Pass the umask-ed create mode to may_o_create() instead of the original one.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Tested-by: Richard W.M. Jones <rjones@redhat.com>
Don't mask S_ISREG off the create mode before passing to ->atomic_open(). Other
methods (->create, ->mknod) also get the complete file mode and filesystems
expect it.
Reported-by: Steve <steveamigauk@yahoo.co.uk>
Reported-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Tested-by: Richard W.M. Jones <rjones@redhat.com>
Currently, mnt_want_write() is sometimes called with i_mutex held and sometimes
without it. This isn't really a problem because mnt_want_write() is a
non-blocking operation (essentially has a trylock semantics) but when the
function starts to handle also frozen filesystems, it will get a full lock
semantics and thus proper lock ordering has to be established. So move
all mnt_want_write() calls outside of i_mutex.
One non-trivial case needing conversion is kern_path_create() /
user_path_create() which didn't include mnt_want_write() but now needs to
because it acquires i_mutex. Because there are virtual file systems which
don't bother with freeze / remount-ro protection we actually provide both
versions of the function - one which calls mnt_want_write() and one which does
not.
[AV: scratch the previous, mnt_want_write() has been moved to kern_path_create()
by now]
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
The write ref to vfsmount taken in lookup_open()/atomic_open() is going to
be dropped; we take the one to stay in dentry_open(). Just grab the temporary
in caller if it looks like we are going to need it (create/truncate/writable open)
and pass (by value) "has it succeeded" flag. Instead of doing mnt_want_write()
inside, check that flag and treat "false" as "mnt_want_write() has just failed".
mnt_want_write() is cheap and the things get considerably simpler and more robust
that way - we get it and drop it in the same function, to start with, rather
than passing a "has something in the guts of really scary functions taken it"
back to caller.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
O_EXCL without O_CREAT has different semantics; it's "fail if already opened",
not "fail if already exists". commit 71574865 broke that...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Adds audit messages for unexpected link restriction violations so that
system owners will have some sort of potentially actionable information
about misbehaving processes.
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This adds symlink and hardlink restrictions to the Linux VFS.
Symlinks:
A long-standing class of security issues is the symlink-based
time-of-check-time-of-use race, most commonly seen in world-writable
directories like /tmp. The common method of exploitation of this flaw
is to cross privilege boundaries when following a given symlink (i.e. a
root process follows a symlink belonging to another user). For a likely
incomplete list of hundreds of examples across the years, please see:
http://cve.mitre.org/cgi-bin/cvekey.cgi?keyword=/tmp
The solution is to permit symlinks to only be followed when outside
a sticky world-writable directory, or when the uid of the symlink and
follower match, or when the directory owner matches the symlink's owner.
Some pointers to the history of earlier discussion that I could find:
1996 Aug, Zygo Blaxell
http://marc.info/?l=bugtraq&m=87602167419830&w=2
1996 Oct, Andrew Tridgell
http://lkml.indiana.edu/hypermail/linux/kernel/9610.2/0086.html
1997 Dec, Albert D Cahalan
http://lkml.org/lkml/1997/12/16/4
2005 Feb, Lorenzo Hernández García-Hierro
http://lkml.indiana.edu/hypermail/linux/kernel/0502.0/1896.html
2010 May, Kees Cook
https://lkml.org/lkml/2010/5/30/144
Past objections and rebuttals could be summarized as:
- Violates POSIX.
- POSIX didn't consider this situation and it's not useful to follow
a broken specification at the cost of security.
- Might break unknown applications that use this feature.
- Applications that break because of the change are easy to spot and
fix. Applications that are vulnerable to symlink ToCToU by not having
the change aren't. Additionally, no applications have yet been found
that rely on this behavior.
- Applications should just use mkstemp() or O_CREATE|O_EXCL.
- True, but applications are not perfect, and new software is written
all the time that makes these mistakes; blocking this flaw at the
kernel is a single solution to the entire class of vulnerability.
- This should live in the core VFS.
- This should live in an LSM. (https://lkml.org/lkml/2010/5/31/135)
- This should live in an LSM.
- This should live in the core VFS. (https://lkml.org/lkml/2010/8/2/188)
Hardlinks:
On systems that have user-writable directories on the same partition
as system files, a long-standing class of security issues is the
hardlink-based time-of-check-time-of-use race, most commonly seen in
world-writable directories like /tmp. The common method of exploitation
of this flaw is to cross privilege boundaries when following a given
hardlink (i.e. a root process follows a hardlink created by another
user). Additionally, an issue exists where users can "pin" a potentially
vulnerable setuid/setgid file so that an administrator will not actually
upgrade a system fully.
The solution is to permit hardlinks to only be created when the user is
already the existing file's owner, or if they already have read/write
access to the existing file.
Many Linux users are surprised when they learn they can link to files
they have no access to, so this change appears to follow the doctrine
of "least surprise". Additionally, this change does not violate POSIX,
which states "the implementation may require that the calling process
has permission to access the existing file"[1].
This change is known to break some implementations of the "at" daemon,
though the version used by Fedora and Ubuntu has been fixed[2] for
a while. Otherwise, the change has been undisruptive while in use in
Ubuntu for the last 1.5 years.
[1] http://pubs.opengroup.org/onlinepubs/9699919799/functions/linkat.html
[2] http://anonscm.debian.org/gitweb/?p=collab-maint/at.git;a=commitdiff;h=f4114656c3a6c6f6070e315ffdf940a49eda3279
This patch is based on the patches in Openwall and grsecurity, along with
suggestions from Al Viro. I have added a sysctl to enable the protected
behavior, and documentation.
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
One side effect - attempt to create a cross-device link on a read-only fs fails
with EROFS instead of EXDEV now. Makes more sense, POSIX allows, etc.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Note that applying umask can't affect their results. While
that affects errno in cases like
mknod("/no_such_directory/a", 030000)
yielding -EINVAL (due to impossible mode_t) instead of
-ENOENT (due to inexistent directory), IMO that makes a lot
more sense, POSIX allows to return either and any software
that relies on getting -ENOENT instead of -EINVAL in that
case deserves everything it gets.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Split inode_permission() into inode- and superblock-dependent parts.
This is aimed at unionmounts where the superblock from the upper layer has to
be checked rather than the superblock from the lower layer as the upper layer
may be writable, thus allowing an unwritable file from the lower layer to be
copied up and modified.
Original-author: Valerie Aurora <vaurora@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com> (Further development)
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Add comments describing what the directions "up" and "down" mean and ref count
handling to the VFS mount following family of functions.
Signed-off-by: Valerie Aurora <vaurora@redhat.com> (Original author)
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Add a helper that abstracts out the jump to an already parsed struct path
from ->follow_link operation from procfs. Not only does this clean up
the code by moving the two sides of this game into a single helper, but
it also prepares for making struct nameidata private to namei.c
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Currently the non-nd_set_link based versions of ->follow_link are expected
to do a path_put(&nd->path) on failure. This calling convention is unexpected,
undocumented and doesn't match what the nd_set_link-based instances do.
Move the path_put out of the only non-nd_set_link based ->follow_link
instance into the caller.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
all callers want the same thing, actually - a kinda-sorta analog of
kern_path_create(). I.e. they want parent vfsmount/dentry (with
->i_mutex held, to make sure the child dentry is still their child)
+ the child dentry.
Signed-off-by Al Viro <viro@zeniv.linux.org.uk>
Since commit 197e37d9, the banner comment on lookup_open() no longer matches
what the function returns. It used to return a struct file pointer or NULL and
now it returns an integer and is passed the struct file pointer it is to use
amongst its arguments. Update the comment to reflect this.
Also add a banner comment to atomic_open().
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
boolean "does it have to be exclusive?" flag is passed instead;
Local filesystem should just ignore it - the object is guaranteed
not to be there yet.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Just the flags; only NFS cares even about that, but there are
legitimate uses for such argument. And getting rid of that
completely would require splitting ->lookup() into a couple
of methods (at least), so let's leave that alone for now...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Just pass struct file *. Methods are happier that way...
There's no need to return struct file * from finish_open() now,
so let it return int. Next: saner prototypes for parts in
namei.c
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Change of calling conventions:
old new
NULL 1
file 0
ERR_PTR(-ve) -ve
Caller *knows* that struct file *; no need to return it.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
... and let finish_open() report having opened the file via that sucker.
Next step: don't modify od->filp at all.
[AV: FILE_CREATE was already used by cifs; Miklos' fix folded]
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Perform open_check_o_direct() in a common place in do_last after opening the
file.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Move the lookup retry logic to the bottom of the function to make the normal
case simpler to read.
Reported-by: David Howells <dhowells@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Consistently use bool for boolean values in do_last().
Reported-by: David Howells <dhowells@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
All users of open intents have been converted to use ->atomic_{open,create}.
This patch gets rid of nd->intent.open and related infrastructure.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Add a new inode operation which is called on the last component of an open.
Using this the filesystem can look up, possibly create and open the file in one
atomic operation. If it cannot perform this (e.g. the file type turned out to
be wrong) it may signal this by returning NULL instead of an open struct file
pointer.
i_op->atomic_open() is only called if the last component is negative or needs
lookup. Handling cached positive dentries here doesn't add much value: these
can be opened using f_op->open(). If the cached file turns out to be invalid,
the open can be retried, this time using ->atomic_open() with a fresh dentry.
For now leave the old way of using open intents in lookup and revalidate in
place. This will be removed once all the users are converted.
David Howells noticed that if ->atomic_open() opens the file but does not create
it, handle_truncate() will be called on it even if it is not a regular file.
Fix this by checking the file type in this case too.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Copy __lookup_hash() into lookup_open(). The next patch will insert the atomic
open call just before the real lookup.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Split out lookup + maybe create from do_last(). This is the part under i_mutex
protection.
The function is called lookup_open() and returns a filp even though the open
part is not used yet.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Make the slow lookup part of O_CREAT and non-O_CREAT opens common.
This allows atomic_open to be hooked into the slow lookup part.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Check O_CREAT on the slow lookup paths where necessary. This allows the rest to
be shared with plain open.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
no need for kludgy "set cookie to ERR_PTR(...) because we failed
before we did actual ->follow_link() and want to suppress put_link()",
no pointless check in put_link() itself.
Callers checked if follow_link() has failed anyway; might as well
break out of their loops if that happened, without bothering
to call put_link() first.
[AV: folded fixes from hch]
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
NFS optimizes away d_revalidates for last component of open. This means that
open itself can find the dentry stale.
This patch allows the filesystem to return EOPENSTALE and the VFS will retry the
lookup on just the last component if possible.
If the lookup was done using RCU mode, including the last component, then this
is not possible since the parent dentry is lost. In this case fall back to
non-RCU lookup. Currently this is not used since NFS will always leave RCU
mode.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Now the post lookup code can be shared between O_CREAT and plain opens since
they are essentially the same.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This allows this code to be shared between O_CREAT and plain opens.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This allows this code to be shared between O_CREAT and plain opens.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Check for ENOTDIR before finishing open. This allows this code to be shared
between O_CREAT and plain opens.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Use helper variable instead of path->dentry->d_inode before complete_walk().
This will allow this code to be used in RCU mode.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Allow returning from do_last() with LOOKUP_RCU still set on the "out:" and
"exit:" labels.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Split do_lookup() into two functions:
lookup_fast() - does cached lookup without i_mutex
lookup_slow() - does lookup with i_mutex
Both follow managed dentries.
The new functions are needed by atomic_open.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
lglocks and brlocks are currently generated with some complicated macros
in lglock.h. But there's no reason to not just use common utility
functions and put all the data into a common data structure.
In preparation, this patch changes the API to look more like normal
function calls with pointers, not magic macros.
The patch is rather large because I move over all users in one go to keep
it bisectable. This impacts the VFS somewhat in terms of lines changed.
But no actual behaviour change.
[akpm@linux-foundation.org: checkpatch fixes]
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This changes the interfaces in <asm/word-at-a-time.h> to be a bit more
complicated, but a lot more generic.
In particular, it allows us to really do the operations efficiently on
both little-endian and big-endian machines, pretty much regardless of
machine details. For example, if you can rely on a fast population
count instruction on your architecture, this will allow you to make your
optimized <asm/word-at-a-time.h> file with that.
NOTE! The "generic" version in include/asm-generic/word-at-a-time.h is
not truly generic, it actually only works on big-endian. Why? Because
on little-endian the generic algorithms are wasteful, since you can
inevitably do better. The x86 implementation is an example of that.
(The only truly non-generic part of the asm-generic implementation is
the "find_zero()" function, and you could make a little-endian version
of it. And if the Kbuild infrastructure allowed us to pick a particular
header file, that would be lovely)
The <asm/word-at-a-time.h> functions are as follows:
- WORD_AT_A_TIME_CONSTANTS: specific constants that the algorithm
uses.
- has_zero(): take a word, and determine if it has a zero byte in it.
It gets the word, the pointer to the constant pool, and a pointer to
an intermediate "data" field it can set.
This is the "quick-and-dirty" zero tester: it's what is run inside
the hot loops.
- "prep_zero_mask()": take the word, the data that has_zero() produced,
and the constant pool, and generate an *exact* mask of which byte had
the first zero. This is run directly *outside* the loop, and allows
the "has_zero()" function to answer the "is there a zero byte"
question without necessarily getting exactly *which* byte is the
first one to contain a zero.
If you do multiple byte lookups concurrently (eg "hash_name()", which
looks for both NUL and '/' bytes), after you've done the prep_zero_mask()
phase, the result of those can be or'ed together to get the "either
or" case.
- The result from "prep_zero_mask()" can then be fed into "find_zero()"
(to find the byte offset of the first byte that was zero) or into
"zero_bytemask()" (to find the bytemask of the bytes preceding the
zero byte).
The existence of zero_bytemask() is optional, and is not necessary
for the normal string routines. But dentry name hashing needs it, so
if you enable DENTRY_WORD_AT_A_TIME you need to expose it.
This changes the generic strncpy_from_user() function and the dentry
hashing functions to use these modified word-at-a-time interfaces. This
gets us back to the optimized state of the x86 strncpy that we lost in
the previous commit when moving over to the generic version.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull sparc changes from David S. Miller:
"This has the generic strncpy_from_user() implementation architectures
can now use, which we've been developing on linux-arch over the past
few days.
For good measure I ran both a 32-bit and a 64-bit glibc testsuite run,
and the latter of which pointed out an adjustment I needed to make to
sparc's user_addr_max() definition. Linus, you were right, STACK_TOP
was not the right thing to use, even on sparc itself :-)
From Sam Ravnborg, we have a conversion of sparc32 over to the common
alloc_thread_info_node(), since the aspect which originally blocked
our doing so (sun4c) has been removed."
Fix up trivial arch/sparc/Kconfig and lib/Makefile conflicts.
* git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc:
sparc: Fix user_addr_max() definition.
lib: Sparc's strncpy_from_user is generic enough, move under lib/
kernel: Move REPEAT_BYTE definition into linux/kernel.h
sparc: Increase portability of strncpy_from_user() implementation.
sparc: Optimize strncpy_from_user() zero byte search.
sparc: Add full proper error handling to strncpy_from_user().
sparc32: use the common implementation of alloc_thread_info_node()
Pull user namespace enhancements from Eric Biederman:
"This is a course correction for the user namespace, so that we can
reach an inexpensive, maintainable, and reasonably complete
implementation.
Highlights:
- Config guards make it impossible to enable the user namespace and
code that has not been converted to be user namespace safe.
- Use of the new kuid_t type ensures the if you somehow get past the
config guards the kernel will encounter type errors if you enable
user namespaces and attempt to compile in code whose permission
checks have not been updated to be user namespace safe.
- All uids from child user namespaces are mapped into the initial
user namespace before they are processed. Removing the need to add
an additional check to see if the user namespace of the compared
uids remains the same.
- With the user namespaces compiled out the performance is as good or
better than it is today.
- For most operations absolutely nothing changes performance or
operationally with the user namespace enabled.
- The worst case performance I could come up with was timing 1
billion cache cold stat operations with the user namespace code
enabled. This went from 156s to 164s on my laptop (or 156ns to
164ns per stat operation).
- (uid_t)-1 and (gid_t)-1 are reserved as an internal error value.
Most uid/gid setting system calls treat these value specially
anyway so attempting to use -1 as a uid would likely cause
entertaining failures in userspace.
- If setuid is called with a uid that can not be mapped setuid fails.
I have looked at sendmail, login, ssh and every other program I
could think of that would call setuid and they all check for and
handle the case where setuid fails.
- If stat or a similar system call is called from a context in which
we can not map a uid we lie and return overflowuid. The LFS
experience suggests not lying and returning an error code might be
better, but the historical precedent with uids is different and I
can not think of anything that would break by lying about a uid we
can't map.
- Capabilities are localized to the current user namespace making it
safe to give the initial user in a user namespace all capabilities.
My git tree covers all of the modifications needed to convert the core
kernel and enough changes to make a system bootable to runlevel 1."
Fix up trivial conflicts due to nearby independent changes in fs/stat.c
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (46 commits)
userns: Silence silly gcc warning.
cred: use correct cred accessor with regards to rcu read lock
userns: Convert the move_pages, and migrate_pages permission checks to use uid_eq
userns: Convert cgroup permission checks to use uid_eq
userns: Convert tmpfs to use kuid and kgid where appropriate
userns: Convert sysfs to use kgid/kuid where appropriate
userns: Convert sysctl permission checks to use kuid and kgids.
userns: Convert proc to use kuid/kgid where appropriate
userns: Convert ext4 to user kuid/kgid where appropriate
userns: Convert ext3 to use kuid/kgid where appropriate
userns: Convert ext2 to use kuid/kgid where appropriate.
userns: Convert devpts to use kuid/kgid where appropriate
userns: Convert binary formats to use kuid/kgid where appropriate
userns: Add negative depends on entries to avoid building code that is userns unsafe
userns: signal remove unnecessary map_cred_ns
userns: Teach inode_capable to understand inodes whose uids map to other namespaces.
userns: Fail exec for suid and sgid binaries with ids outside our user namespace.
userns: Convert stat to return values mapped from kuids and kgids
userns: Convert user specfied uids and gids in chown into kuids and kgid
userns: Use uid_eq gid_eq helpers when comparing kuids and kgids in the vfs
...
This branch simplifies and clarifies the dcache lookup, and allows us to
do certain nice optimizations when comparing dentries. It also cleans
up the interface to __d_lookup_rcu(), especially around passing the
inode information around.
* dentry-cleanups:
vfs: make it possible to access the dentry hash/len as one 64-bit entry
vfs: move dentry name length comparison from dentry_cmp() into callers
vfs: do the careful dentry name access for all dentry_cmp cases
vfs: remove unnecessary d_unhashed() check from __d_lookup_rcu
vfs: clean up __d_lookup_rcu() and dentry_cmp() interfaces
This teaches vfs_fstat() to use the appropriate f[get|put]_light
functions, allowing it to avoid some unnecessary locking for the common
case.
More noticeably, it also cleans up and simplifies the "getname_flags()"
function, which now relies on the architecture strncpy_from_user() doing
all the user access checks properly, instead of hacking around the fact
that on x86 it didn't use to do it right (see commit 92ae03f2ef: "x86:
merge 32/64-bit versions of 'strncpy_from_user()' and speed it up").
* vfs-cleanups:
VFS: make vfs_fstat() use f[get|put]_light()
VFS: clean up and simplify getname_flags()
x86: make word-at-a-time strncpy_from_user clear bytes at the end
The calling conventions for __d_lookup_rcu() and dentry_cmp() are
annoying in different ways, and there is actually one single underlying
reason for both of the annoyances.
The fundamental reason is that we do the returned dentry sequence number
check inside __d_lookup_rcu() instead of doing it in the caller. This
results in two annoyances:
- __d_lookup_rcu() now not only needs to return the dentry and the
sequence number that goes along with the lookup, it also needs to
return the inode pointer that was validated by that sequence number
check.
- and because we did the sequence number check early (to validate the
name pointer and length) we also couldn't just pass the dentry itself
to dentry_cmp(), we had to pass the counted string that contained the
name.
So that sequence number decision caused two separate ugly calling
conventions.
Both of these problems would be solved if we just did the sequence
number check in the caller instead. There's only one caller, and that
caller already has to do the sequence number check for the parent
anyway, so just do that.
That allows us to stop returning the dentry->d_inode in that in-out
argument (pointer-to-pointer-to-inode), so we can make the inode
argument just a regular input inode pointer. The caller can just load
the inode from dentry->d_inode, and then do the sequence number check
after that to make sure that it's synchronized with the name we looked
up.
And it allows us to just pass in the dentry to dentry_cmp(), which is
what all the callers really wanted. Sure, dentry_cmp() has to be a bit
careful about the dentry (which is not stable during RCU lookup), but
that's actually very simple.
And now that dentry_cmp() can clearly see that the first string argument
is a dentry, we can use the direct word access for that, instead of the
careful unaligned zero-padding. The dentry name is always properly
aligned, since it is a single path component that is either embedded
into the dentry itself, or was allocated with kmalloc() (see __d_alloc).
Finally, this also uninlines the nasty slow-case for dentry comparisons:
that one *does* need to do a sequence number check, since it will call
in to the low-level filesystems, and we want to give those a stable
inode pointer and path component length/start arguments. Doing an extra
sequence check for that slow case is not a problem, though.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
It turns out that there are more cases than CONFIG_DEBUG_PAGEALLOC that
can have holes in the kernel address space: it seems to happen easily
with Xen, and it looks like the AMD gart64 code will also punch holes
dynamically.
Actually hitting that case is still very unlikely, so just do the
access, and take an exception and fix it up for the very unlikely case
of it being a page-crosser with no next page.
And hey, this abstraction might even help other architectures that have
other issues with unaligned word accesses than the possible missing next
page. IOW, this could do the byte order magic too.
Peter Anvin fixed a thinko in the shifting for the exception case.
Reported-and-tested-by: Jana Saout <jana@saout.de>
Cc: Peter Anvin <hpa@zytor.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This removes a number of silly games around strncpy_from_user() in
do_getname(), and removes that helper function entirely. We instead
make getname_flags() just use strncpy_from_user() properly directly.
Removing the wrapper function simplifies things noticeably, mostly
because we no longer play the unnecessary games with segments (x86
strncpy_from_user() no longer needs the hack), but also because the
empty path handling is just much more obvious. The return value of
"strncpy_to_user()" is much more obvious than checking an odd error
return case from do_getname().
[ non-x86 architectures were notified of this change several weeks ago,
since it is possible that they have copied the old broken x86
strncpy_from_user. But nobody reacted, so .. See
http://www.spinics.net/lists/linux-arch/msg17313.html
for details ]
Cc: linux-arch@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This represents a change in strategy of how to handle user namespaces.
Instead of tagging everything explicitly with a user namespace and bulking
up all of the comparisons of uids and gids in the kernel, all uids and gids
in use will have a mapping to a flat kuid and kgid spaces respectively. This
allows much more of the existing logic to be preserved and in general
allows for faster code.
In this new and improved world we allow someone to utiliize capabilities
over an inode if the inodes owner mapps into the capabilities holders user
namespace and the user has capabilities in their user namespace. Which
is simple and efficient.
Moving the fs uid comparisons to be comparisons in a flat kuid space
follows in later patches, something that is only significant if you
are using user namespaces.
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
I have a new optimized x86 "strncpy_from_user()" that will use these
same helper functions for all the same reasons the name lookup code uses
them. This is preparation for that.
This moves them into an architecture-specific header file. It's
architecture-specific for two reasons:
- some of the functions are likely to want architecture-specific
implementations. Even if the current code happens to be "generic" in
the sense that it should work on any little-endian machine, it's
likely that the "multiply by a big constant and shift" implementation
is less than optimal for an architecture that has a guaranteed fast
bit count instruction, for example.
- I expect that if architectures like sparc want to start playing
around with this, we'll need to abstract out a few more details (in
particular the actual unaligned accesses). So we're likely to have
more architecture-specific stuff if non-x86 architectures start using
this.
(and if it turns out that non-x86 architectures don't start using
this, then having it in an architecture-specific header is still the
right thing to do, of course)
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Safely making device nodes in a container is solvable but simply
having the capability in a user namespace is not sufficient to make
this work.
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
64252c75a2 "vfs: remove dget() from
dentry_unhash()" changed the implementation but not the comment.
Cc: Sage Weil <sage@newdream.net>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Split __lookup_hash into two component functions:
lookup_dcache - tries cached lookup, returns whether real lookup is needed
lookup_real - calls i_op->lookup
This eliminates code duplication between d_alloc_and_lookup() and
d_inode_lookup().
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Everything arriving into if (!dentry) will have need_reval = 1.
Indeed, the only way to get there with need_reval reset to 0 would
be via
if (unlikely(d_need_lookup(dentry)))
goto unlazy;
if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
status = d_revalidate(dentry, nd);
if (unlikely(status <= 0)) {
if (status != -ECHILD)
need_reval = 0;
goto unlazy;
...
unlazy:
/* no assignments to dentry */
if (dentry && unlikely(d_need_lookup(dentry))) {
dput(dentry);
dentry = NULL;
}
and if d_need_lookup() had already been false the first time around, it
will remain false on the second call as well.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
d_lookup() *will* fail after successful d_invalidate(), if we are
holding i_mutex all along. IOW, we don't need to jump back to
l: - we know what path will be taken there and can do that (i.e.
d_alloc_and_lookup()) directly.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Duplicate the revalidation-related parts into if (!dentry) branch.
Next step will be to pull them under i_mutex.
This and the next 8 commits are more or less a splitup of patch
by Miklos; folks, when you are working with something that convoluted,
carve your patches up into easily reviewed steps, especially when
a lot of codepaths involved are rarely hit...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
The only caller of __lookup_hash() that needs the exec permission check on
parent is lookup_one_len().
All lookup_hash() callers already checked permission in LOOKUP_PARENT walk.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
__lookup_hash() calls ->lookup() if the dentry needs lookup and on success
revalidates the dentry (all under dir->i_mutex).
While this is harmless it doesn't make a lot of sense.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Doing revalidate on a dentry which has not yet been looked up makes no sense.
Move the d_need_lookup() check before d_revalidate().
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
"[PATCH 0/3] RFC - module.h usage cleanups in fs/ and lib/"
https://lkml.org/lkml/2012/2/29/589
--
Fix up files in fs/ and lib/ dirs to only use module.h if they really
need it.
These are trivial in scope vs. the work done previously. We now have
things where any few remaining cleanups can be farmed out to arch or
subsystem maintainers, and I have done so when possible. What is
remaining here represents the bits that don't clearly lie within a
single arch/subsystem boundary, like the fs dir and the lib dir.
Some duplicate includes arising from overlapping fixes from
independent subsystem maintainer submissions are also quashed.
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Merge tag 'module-for-3.4' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux
Pull cleanup of fs/ and lib/ users of module.h from Paul Gortmaker:
"Fix up files in fs/ and lib/ dirs to only use module.h if they really
need it.
These are trivial in scope vs the work done previously. We now have
things where any few remaining cleanups can be farmed out to arch or
subsystem maintainers, and I have done so when possible. What is
remaining here represents the bits that don't clearly lie within a
single arch/subsystem boundary, like the fs dir and the lib dir.
Some duplicate includes arising from overlapping fixes from
independent subsystem maintainer submissions are also quashed."
Fix up trivial conflicts due to clashes with other include file cleanups
(including some due to the previous bug.h cleanup pull).
* tag 'module-for-3.4' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux:
lib: reduce the use of module.h wherever possible
fs: reduce the use of module.h wherever possible
includecheck: delete any duplicate instances of module.h
While doing the fs/namei.c cleanups, I ran sparse on it, and it pointed
out other large integers and a couple of cases of us using '0' instead
of the proper 'NULL'.
Sparse still doesn't understand some of the conditional locking going
on, but that's no excuse for not fixing up the trivial stuff.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In commit commit 1de5b41cd3 ("fs/namei.c: fix warnings on 32-bit")
Andrew said that there must be a tidier way of doing this.
This is that tidier way.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We want it to match what hash_name() is doing, which means extra
multiply by 9 in this case...
Reported-and-Tested-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Merge first batch of patches from Andrew Morton:
"A few misc things and all the MM queue"
* emailed from Andrew Morton <akpm@linux-foundation.org>: (92 commits)
memcg: avoid THP split in task migration
thp: add HPAGE_PMD_* definitions for !CONFIG_TRANSPARENT_HUGEPAGE
memcg: clean up existing move charge code
mm/memcontrol.c: remove unnecessary 'break' in mem_cgroup_read()
mm/memcontrol.c: remove redundant BUG_ON() in mem_cgroup_usage_unregister_event()
mm/memcontrol.c: s/stealed/stolen/
memcg: fix performance of mem_cgroup_begin_update_page_stat()
memcg: remove PCG_FILE_MAPPED
memcg: use new logic for page stat accounting
memcg: remove PCG_MOVE_LOCK flag from page_cgroup
memcg: simplify move_account() check
memcg: remove EXPORT_SYMBOL(mem_cgroup_update_page_stat)
memcg: kill dead prev_priority stubs
memcg: remove PCG_CACHE page_cgroup flag
memcg: let css_get_next() rely upon rcu_read_lock()
cgroup: revert ss_id_lock to spinlock
idr: make idr_get_next() good for rcu_read_lock()
memcg: remove unnecessary thp check in page stat accounting
memcg: remove redundant returns
memcg: enum lru_list lru
...
i386 allnoconfig:
fs/namei.c: In function 'has_zero':
fs/namei.c:1617: warning: integer constant is too large for 'unsigned long' type
fs/namei.c:1617: warning: integer constant is too large for 'unsigned long' type
fs/namei.c: In function 'hash_name':
fs/namei.c:1635: warning: integer constant is too large for 'unsigned long' type
There must be a tidier way of doing this.
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull vfs pile 1 from Al Viro:
"This is _not_ all; in particular, Miklos' and Jan's stuff is not there
yet."
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (64 commits)
ext4: initialization of ext4_li_mtx needs to be done earlier
debugfs-related mode_t whack-a-mole
hfsplus: add an ioctl to bless files
hfsplus: change finder_info to u32
hfsplus: initialise userflags
qnx4: new helper - try_extent()
qnx4: get rid of qnx4_bread/qnx4_getblk
take removal of PF_FORKNOEXEC to flush_old_exec()
trim includes in inode.c
um: uml_dup_mmap() relies on ->mmap_sem being held, but activate_mm() doesn't hold it
um: embed ->stub_pages[] into mmu_context
gadgetfs: list_for_each_safe() misuse
ocfs2: fix leaks on failure exits in module_init
ecryptfs: make register_filesystem() the last potential failure exit
ntfs: forgets to unregister sysctls on register_filesystem() failure
logfs: missing cleanup on register_filesystem() failure
jfs: mising cleanup on register_filesystem() failure
make configfs_pin_fs() return root dentry on success
configfs: configfs_create_dir() has parent dentry in dentry->d_parent
configfs: sanitize configfs_create()
...
Pull kmap_atomic cleanup from Cong Wang.
It's been in -next for a long time, and it gets rid of the (no longer
used) second argument to k[un]map_atomic().
Fix up a few trivial conflicts in various drivers, and do an "evil
merge" to catch some new uses that have come in since Cong's tree.
* 'kmap_atomic' of git://github.com/congwang/linux: (59 commits)
feature-removal-schedule.txt: schedule the deprecated form of kmap_atomic() for removal
highmem: kill all __kmap_atomic() [swarren@nvidia.com: highmem: Fix ARM build break due to __kmap_atomic rename]
drbd: remove the second argument of k[un]map_atomic()
zcache: remove the second argument of k[un]map_atomic()
gma500: remove the second argument of k[un]map_atomic()
dm: remove the second argument of k[un]map_atomic()
tomoyo: remove the second argument of k[un]map_atomic()
sunrpc: remove the second argument of k[un]map_atomic()
rds: remove the second argument of k[un]map_atomic()
net: remove the second argument of k[un]map_atomic()
mm: remove the second argument of k[un]map_atomic()
lib: remove the second argument of k[un]map_atomic()
power: remove the second argument of k[un]map_atomic()
kdb: remove the second argument of k[un]map_atomic()
udf: remove the second argument of k[un]map_atomic()
ubifs: remove the second argument of k[un]map_atomic()
squashfs: remove the second argument of k[un]map_atomic()
reiserfs: remove the second argument of k[un]map_atomic()
ocfs2: remove the second argument of k[un]map_atomic()
ntfs: remove the second argument of k[un]map_atomic()
...
New field of struct super_block - ->s_max_links. Maximal allowed
value of ->i_nlink or 0; in the latter case all checks still need
to be done in ->link/->mkdir/->rename instances. Note that this
limit applies both to directoris and to non-directories.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* branch 'dcache-word-accesses':
vfs: use 'unsigned long' accesses for dcache name comparison and hashing
This does the name hashing and lookup using word-sized accesses when
that is efficient, namely on x86 (although any little-endian machine
with good unaligned accesses would do).
It does very much depend on little-endian logic, but it's a very hot
couple of functions under some real loads, and this patch improves the
performance of __d_lookup_rcu() and link_path_walk() by up to about 30%.
Giving a 10% improvement on some very pathname-heavy benchmarks.
Because we do make unaligned accesses past the filename, the
optimization is disabled when CONFIG_DEBUG_PAGEALLOC is active, and we
effectively depend on the fact that on x86 we don't really ever have the
last page of usable RAM followed immediately by any IO memory (due to
ACPI tables, BIOS buffer areas etc).
Some of the bit operations we do are a bit "subtle". It's commented,
but you do need to really think about the code. Or just consider it
black magic.
Thanks to people on G+ for some of the optimized bit tricks.
complete_walk() returns either ECHILD or ESTALE. do_last() turns this into
ECHILD unconditionally. If not in RCU mode, this error will reach userspace
which is complete nonsense.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
CC: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
complete_walk() already puts nd->path, no need to do it again at cleanup time.
This would result in Oopses if triggered, apparently the codepath is not too
well exercised.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
CC: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
