kernel-ark/fs/cachefiles/interface.c
David Howells a818101d7b cachefiles: Fix attempt to read i_blocks after deleting file [ver #2]
An NULL-pointer dereference happens in cachefiles_mark_object_inactive()
when it tries to read i_blocks so that it can tell the cachefilesd daemon
how much space it's making available.

The problem is that cachefiles_drop_object() calls
cachefiles_mark_object_inactive() after calling cachefiles_delete_object()
because the object being marked active staves off attempts to (re-)use the
file at that filename until after it has been deleted.  This means that
d_inode is NULL by the time we come to try to access it.

To fix the problem, have the caller of cachefiles_mark_object_inactive()
supply the number of blocks freed up.

Without this, the following oops may occur:

BUG: unable to handle kernel NULL pointer dereference at 0000000000000098
IP: [<ffffffffa06c5cc1>] cachefiles_mark_object_inactive+0x61/0xb0 [cachefiles]
...
CPU: 11 PID: 527 Comm: kworker/u64:4 Tainted: G          I    ------------   3.10.0-470.el7.x86_64 #1
Hardware name: Hewlett-Packard HP Z600 Workstation/0B54h, BIOS 786G4 v03.19 03/11/2011
Workqueue: fscache_object fscache_object_work_func [fscache]
task: ffff880035edaf10 ti: ffff8800b77c0000 task.ti: ffff8800b77c0000
RIP: 0010:[<ffffffffa06c5cc1>] cachefiles_mark_object_inactive+0x61/0xb0 [cachefiles]
RSP: 0018:ffff8800b77c3d70  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8800bf6cc400 RCX: 0000000000000034
RDX: 0000000000000000 RSI: ffff880090ffc710 RDI: ffff8800bf761ef8
RBP: ffff8800b77c3d88 R08: 2000000000000000 R09: 0090ffc710000000
R10: ff51005d2ff1c400 R11: 0000000000000000 R12: ffff880090ffc600
R13: ffff8800bf6cc520 R14: ffff8800bf6cc400 R15: ffff8800bf6cc498
FS:  0000000000000000(0000) GS:ffff8800bb8c0000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 0000000000000098 CR3: 00000000019ba000 CR4: 00000000000007e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Stack:
 ffff880090ffc600 ffff8800bf6cc400 ffff8800867df140 ffff8800b77c3db0
 ffffffffa06c48cb ffff880090ffc600 ffff880090ffc180 ffff880090ffc658
 ffff8800b77c3df0 ffffffffa085d846 ffff8800a96b8150 ffff880090ffc600
Call Trace:
 [<ffffffffa06c48cb>] cachefiles_drop_object+0x6b/0xf0 [cachefiles]
 [<ffffffffa085d846>] fscache_drop_object+0xd6/0x1e0 [fscache]
 [<ffffffffa085d615>] fscache_object_work_func+0xa5/0x200 [fscache]
 [<ffffffff810a605b>] process_one_work+0x17b/0x470
 [<ffffffff810a6e96>] worker_thread+0x126/0x410
 [<ffffffff810a6d70>] ? rescuer_thread+0x460/0x460
 [<ffffffff810ae64f>] kthread+0xcf/0xe0
 [<ffffffff810ae580>] ? kthread_create_on_node+0x140/0x140
 [<ffffffff81695418>] ret_from_fork+0x58/0x90
 [<ffffffff810ae580>] ? kthread_create_on_node+0x140/0x140

The oopsing code shows:

	callq  0xffffffff810af6a0 <wake_up_bit>
	mov    0xf8(%r12),%rax
	mov    0x30(%rax),%rax
	mov    0x98(%rax),%rax   <---- oops here
	lock add %rax,0x130(%rbx)

where this is:

	d_backing_inode(object->dentry)->i_blocks

Fixes: a5b3a80b89 (CacheFiles: Provide read-and-reset release counters for cachefilesd)
Reported-by: Jianhong Yin <jiyin@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Steve Dickson <steved@redhat.com>
cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2016-09-27 18:31:29 -04:00

557 lines
15 KiB
C

/* FS-Cache interface to CacheFiles
*
* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*/
#include <linux/slab.h>
#include <linux/mount.h>
#include "internal.h"
struct cachefiles_lookup_data {
struct cachefiles_xattr *auxdata; /* auxiliary data */
char *key; /* key path */
};
static int cachefiles_attr_changed(struct fscache_object *_object);
/*
* allocate an object record for a cookie lookup and prepare the lookup data
*/
static struct fscache_object *cachefiles_alloc_object(
struct fscache_cache *_cache,
struct fscache_cookie *cookie)
{
struct cachefiles_lookup_data *lookup_data;
struct cachefiles_object *object;
struct cachefiles_cache *cache;
struct cachefiles_xattr *auxdata;
unsigned keylen, auxlen;
void *buffer;
char *key;
cache = container_of(_cache, struct cachefiles_cache, cache);
_enter("{%s},%p,", cache->cache.identifier, cookie);
lookup_data = kmalloc(sizeof(*lookup_data), cachefiles_gfp);
if (!lookup_data)
goto nomem_lookup_data;
/* create a new object record and a temporary leaf image */
object = kmem_cache_alloc(cachefiles_object_jar, cachefiles_gfp);
if (!object)
goto nomem_object;
ASSERTCMP(object->backer, ==, NULL);
BUG_ON(test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags));
atomic_set(&object->usage, 1);
fscache_object_init(&object->fscache, cookie, &cache->cache);
object->type = cookie->def->type;
/* get hold of the raw key
* - stick the length on the front and leave space on the back for the
* encoder
*/
buffer = kmalloc((2 + 512) + 3, cachefiles_gfp);
if (!buffer)
goto nomem_buffer;
keylen = cookie->def->get_key(cookie->netfs_data, buffer + 2, 512);
ASSERTCMP(keylen, <, 512);
*(uint16_t *)buffer = keylen;
((char *)buffer)[keylen + 2] = 0;
((char *)buffer)[keylen + 3] = 0;
((char *)buffer)[keylen + 4] = 0;
/* turn the raw key into something that can work with as a filename */
key = cachefiles_cook_key(buffer, keylen + 2, object->type);
if (!key)
goto nomem_key;
/* get hold of the auxiliary data and prepend the object type */
auxdata = buffer;
auxlen = 0;
if (cookie->def->get_aux) {
auxlen = cookie->def->get_aux(cookie->netfs_data,
auxdata->data, 511);
ASSERTCMP(auxlen, <, 511);
}
auxdata->len = auxlen + 1;
auxdata->type = cookie->def->type;
lookup_data->auxdata = auxdata;
lookup_data->key = key;
object->lookup_data = lookup_data;
_leave(" = %p [%p]", &object->fscache, lookup_data);
return &object->fscache;
nomem_key:
kfree(buffer);
nomem_buffer:
BUG_ON(test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags));
kmem_cache_free(cachefiles_object_jar, object);
fscache_object_destroyed(&cache->cache);
nomem_object:
kfree(lookup_data);
nomem_lookup_data:
_leave(" = -ENOMEM");
return ERR_PTR(-ENOMEM);
}
/*
* attempt to look up the nominated node in this cache
* - return -ETIMEDOUT to be scheduled again
*/
static int cachefiles_lookup_object(struct fscache_object *_object)
{
struct cachefiles_lookup_data *lookup_data;
struct cachefiles_object *parent, *object;
struct cachefiles_cache *cache;
const struct cred *saved_cred;
int ret;
_enter("{OBJ%x}", _object->debug_id);
cache = container_of(_object->cache, struct cachefiles_cache, cache);
parent = container_of(_object->parent,
struct cachefiles_object, fscache);
object = container_of(_object, struct cachefiles_object, fscache);
lookup_data = object->lookup_data;
ASSERTCMP(lookup_data, !=, NULL);
/* look up the key, creating any missing bits */
cachefiles_begin_secure(cache, &saved_cred);
ret = cachefiles_walk_to_object(parent, object,
lookup_data->key,
lookup_data->auxdata);
cachefiles_end_secure(cache, saved_cred);
/* polish off by setting the attributes of non-index files */
if (ret == 0 &&
object->fscache.cookie->def->type != FSCACHE_COOKIE_TYPE_INDEX)
cachefiles_attr_changed(&object->fscache);
if (ret < 0 && ret != -ETIMEDOUT) {
if (ret != -ENOBUFS)
pr_warn("Lookup failed error %d\n", ret);
fscache_object_lookup_error(&object->fscache);
}
_leave(" [%d]", ret);
return ret;
}
/*
* indication of lookup completion
*/
static void cachefiles_lookup_complete(struct fscache_object *_object)
{
struct cachefiles_object *object;
object = container_of(_object, struct cachefiles_object, fscache);
_enter("{OBJ%x,%p}", object->fscache.debug_id, object->lookup_data);
if (object->lookup_data) {
kfree(object->lookup_data->key);
kfree(object->lookup_data->auxdata);
kfree(object->lookup_data);
object->lookup_data = NULL;
}
}
/*
* increment the usage count on an inode object (may fail if unmounting)
*/
static
struct fscache_object *cachefiles_grab_object(struct fscache_object *_object)
{
struct cachefiles_object *object =
container_of(_object, struct cachefiles_object, fscache);
_enter("{OBJ%x,%d}", _object->debug_id, atomic_read(&object->usage));
#ifdef CACHEFILES_DEBUG_SLAB
ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
#endif
atomic_inc(&object->usage);
return &object->fscache;
}
/*
* update the auxiliary data for an object object on disk
*/
static void cachefiles_update_object(struct fscache_object *_object)
{
struct cachefiles_object *object;
struct cachefiles_xattr *auxdata;
struct cachefiles_cache *cache;
struct fscache_cookie *cookie;
const struct cred *saved_cred;
unsigned auxlen;
_enter("{OBJ%x}", _object->debug_id);
object = container_of(_object, struct cachefiles_object, fscache);
cache = container_of(object->fscache.cache, struct cachefiles_cache,
cache);
if (!fscache_use_cookie(_object)) {
_leave(" [relinq]");
return;
}
cookie = object->fscache.cookie;
if (!cookie->def->get_aux) {
fscache_unuse_cookie(_object);
_leave(" [no aux]");
return;
}
auxdata = kmalloc(2 + 512 + 3, cachefiles_gfp);
if (!auxdata) {
fscache_unuse_cookie(_object);
_leave(" [nomem]");
return;
}
auxlen = cookie->def->get_aux(cookie->netfs_data, auxdata->data, 511);
fscache_unuse_cookie(_object);
ASSERTCMP(auxlen, <, 511);
auxdata->len = auxlen + 1;
auxdata->type = cookie->def->type;
cachefiles_begin_secure(cache, &saved_cred);
cachefiles_update_object_xattr(object, auxdata);
cachefiles_end_secure(cache, saved_cred);
kfree(auxdata);
_leave("");
}
/*
* discard the resources pinned by an object and effect retirement if
* requested
*/
static void cachefiles_drop_object(struct fscache_object *_object)
{
struct cachefiles_object *object;
struct cachefiles_cache *cache;
const struct cred *saved_cred;
struct inode *inode;
blkcnt_t i_blocks = 0;
ASSERT(_object);
object = container_of(_object, struct cachefiles_object, fscache);
_enter("{OBJ%x,%d}",
object->fscache.debug_id, atomic_read(&object->usage));
cache = container_of(object->fscache.cache,
struct cachefiles_cache, cache);
#ifdef CACHEFILES_DEBUG_SLAB
ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
#endif
/* We need to tidy the object up if we did in fact manage to open it.
* It's possible for us to get here before the object is fully
* initialised if the parent goes away or the object gets retired
* before we set it up.
*/
if (object->dentry) {
/* delete retired objects */
if (test_bit(FSCACHE_OBJECT_RETIRED, &object->fscache.flags) &&
_object != cache->cache.fsdef
) {
_debug("- retire object OBJ%x", object->fscache.debug_id);
inode = d_backing_inode(object->dentry);
if (inode)
i_blocks = inode->i_blocks;
cachefiles_begin_secure(cache, &saved_cred);
cachefiles_delete_object(cache, object);
cachefiles_end_secure(cache, saved_cred);
}
/* close the filesystem stuff attached to the object */
if (object->backer != object->dentry)
dput(object->backer);
object->backer = NULL;
}
/* note that the object is now inactive */
if (test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags))
cachefiles_mark_object_inactive(cache, object, i_blocks);
dput(object->dentry);
object->dentry = NULL;
_leave("");
}
/*
* dispose of a reference to an object
*/
static void cachefiles_put_object(struct fscache_object *_object)
{
struct cachefiles_object *object;
struct fscache_cache *cache;
ASSERT(_object);
object = container_of(_object, struct cachefiles_object, fscache);
_enter("{OBJ%x,%d}",
object->fscache.debug_id, atomic_read(&object->usage));
#ifdef CACHEFILES_DEBUG_SLAB
ASSERT((atomic_read(&object->usage) & 0xffff0000) != 0x6b6b0000);
#endif
ASSERTIFCMP(object->fscache.parent,
object->fscache.parent->n_children, >, 0);
if (atomic_dec_and_test(&object->usage)) {
_debug("- kill object OBJ%x", object->fscache.debug_id);
ASSERT(!test_bit(CACHEFILES_OBJECT_ACTIVE, &object->flags));
ASSERTCMP(object->fscache.parent, ==, NULL);
ASSERTCMP(object->backer, ==, NULL);
ASSERTCMP(object->dentry, ==, NULL);
ASSERTCMP(object->fscache.n_ops, ==, 0);
ASSERTCMP(object->fscache.n_children, ==, 0);
if (object->lookup_data) {
kfree(object->lookup_data->key);
kfree(object->lookup_data->auxdata);
kfree(object->lookup_data);
object->lookup_data = NULL;
}
cache = object->fscache.cache;
fscache_object_destroy(&object->fscache);
kmem_cache_free(cachefiles_object_jar, object);
fscache_object_destroyed(cache);
}
_leave("");
}
/*
* sync a cache
*/
static void cachefiles_sync_cache(struct fscache_cache *_cache)
{
struct cachefiles_cache *cache;
const struct cred *saved_cred;
int ret;
_enter("%p", _cache);
cache = container_of(_cache, struct cachefiles_cache, cache);
/* make sure all pages pinned by operations on behalf of the netfs are
* written to disc */
cachefiles_begin_secure(cache, &saved_cred);
down_read(&cache->mnt->mnt_sb->s_umount);
ret = sync_filesystem(cache->mnt->mnt_sb);
up_read(&cache->mnt->mnt_sb->s_umount);
cachefiles_end_secure(cache, saved_cred);
if (ret == -EIO)
cachefiles_io_error(cache,
"Attempt to sync backing fs superblock"
" returned error %d",
ret);
}
/*
* check if the backing cache is updated to FS-Cache
* - called by FS-Cache when evaluates if need to invalidate the cache
*/
static int cachefiles_check_consistency(struct fscache_operation *op)
{
struct cachefiles_object *object;
struct cachefiles_cache *cache;
const struct cred *saved_cred;
int ret;
_enter("{OBJ%x}", op->object->debug_id);
object = container_of(op->object, struct cachefiles_object, fscache);
cache = container_of(object->fscache.cache,
struct cachefiles_cache, cache);
cachefiles_begin_secure(cache, &saved_cred);
ret = cachefiles_check_auxdata(object);
cachefiles_end_secure(cache, saved_cred);
_leave(" = %d", ret);
return ret;
}
/*
* notification the attributes on an object have changed
* - called with reads/writes excluded by FS-Cache
*/
static int cachefiles_attr_changed(struct fscache_object *_object)
{
struct cachefiles_object *object;
struct cachefiles_cache *cache;
const struct cred *saved_cred;
struct iattr newattrs;
uint64_t ni_size;
loff_t oi_size;
int ret;
_object->cookie->def->get_attr(_object->cookie->netfs_data, &ni_size);
_enter("{OBJ%x},[%llu]",
_object->debug_id, (unsigned long long) ni_size);
object = container_of(_object, struct cachefiles_object, fscache);
cache = container_of(object->fscache.cache,
struct cachefiles_cache, cache);
if (ni_size == object->i_size)
return 0;
if (!object->backer)
return -ENOBUFS;
ASSERT(d_is_reg(object->backer));
fscache_set_store_limit(&object->fscache, ni_size);
oi_size = i_size_read(d_backing_inode(object->backer));
if (oi_size == ni_size)
return 0;
cachefiles_begin_secure(cache, &saved_cred);
inode_lock(d_inode(object->backer));
/* if there's an extension to a partial page at the end of the backing
* file, we need to discard the partial page so that we pick up new
* data after it */
if (oi_size & ~PAGE_MASK && ni_size > oi_size) {
_debug("discard tail %llx", oi_size);
newattrs.ia_valid = ATTR_SIZE;
newattrs.ia_size = oi_size & PAGE_MASK;
ret = notify_change(object->backer, &newattrs, NULL);
if (ret < 0)
goto truncate_failed;
}
newattrs.ia_valid = ATTR_SIZE;
newattrs.ia_size = ni_size;
ret = notify_change(object->backer, &newattrs, NULL);
truncate_failed:
inode_unlock(d_inode(object->backer));
cachefiles_end_secure(cache, saved_cred);
if (ret == -EIO) {
fscache_set_store_limit(&object->fscache, 0);
cachefiles_io_error_obj(object, "Size set failed");
ret = -ENOBUFS;
}
_leave(" = %d", ret);
return ret;
}
/*
* Invalidate an object
*/
static void cachefiles_invalidate_object(struct fscache_operation *op)
{
struct cachefiles_object *object;
struct cachefiles_cache *cache;
const struct cred *saved_cred;
struct path path;
uint64_t ni_size;
int ret;
object = container_of(op->object, struct cachefiles_object, fscache);
cache = container_of(object->fscache.cache,
struct cachefiles_cache, cache);
op->object->cookie->def->get_attr(op->object->cookie->netfs_data,
&ni_size);
_enter("{OBJ%x},[%llu]",
op->object->debug_id, (unsigned long long)ni_size);
if (object->backer) {
ASSERT(d_is_reg(object->backer));
fscache_set_store_limit(&object->fscache, ni_size);
path.dentry = object->backer;
path.mnt = cache->mnt;
cachefiles_begin_secure(cache, &saved_cred);
ret = vfs_truncate(&path, 0);
if (ret == 0)
ret = vfs_truncate(&path, ni_size);
cachefiles_end_secure(cache, saved_cred);
if (ret != 0) {
fscache_set_store_limit(&object->fscache, 0);
if (ret == -EIO)
cachefiles_io_error_obj(object,
"Invalidate failed");
}
}
fscache_op_complete(op, true);
_leave("");
}
/*
* dissociate a cache from all the pages it was backing
*/
static void cachefiles_dissociate_pages(struct fscache_cache *cache)
{
_enter("");
}
const struct fscache_cache_ops cachefiles_cache_ops = {
.name = "cachefiles",
.alloc_object = cachefiles_alloc_object,
.lookup_object = cachefiles_lookup_object,
.lookup_complete = cachefiles_lookup_complete,
.grab_object = cachefiles_grab_object,
.update_object = cachefiles_update_object,
.invalidate_object = cachefiles_invalidate_object,
.drop_object = cachefiles_drop_object,
.put_object = cachefiles_put_object,
.sync_cache = cachefiles_sync_cache,
.attr_changed = cachefiles_attr_changed,
.read_or_alloc_page = cachefiles_read_or_alloc_page,
.read_or_alloc_pages = cachefiles_read_or_alloc_pages,
.allocate_page = cachefiles_allocate_page,
.allocate_pages = cachefiles_allocate_pages,
.write_page = cachefiles_write_page,
.uncache_page = cachefiles_uncache_page,
.dissociate_pages = cachefiles_dissociate_pages,
.check_consistency = cachefiles_check_consistency,
};