Fix dmesg_restrict patch to avoid regression (rhbz 952655)
This commit is contained in:
Josh Boyer
parent
4751fcd387
commit
89560ac259
|
|
@ -1,33 +1,106 @@
|
|||
From ce10d1b72b4da3c98bbbcb1b945687d964c31923 Mon Sep 17 00:00:00 2001
|
||||
From: Josh Boyer <jwboyer@redhat.com>
|
||||
Date: Tue, 9 Apr 2013 11:08:13 -0400
|
||||
Subject: [PATCH] kmsg: Honor dmesg_restrict sysctl on /dev/kmsg
|
||||
To fix /dev/kmsg, let's compare the existing interfaces and what they allow:
|
||||
|
||||
The dmesg_restrict sysctl currently covers the syslog method for access
|
||||
dmesg, however /dev/kmsg isn't covered by the same protections. Most
|
||||
people haven't noticed because util-linux dmesg(1) defaults to using the
|
||||
syslog method for access in older versions. With util-linux dmesg(1)
|
||||
defaults to reading directly from /dev/kmsg.
|
||||
- /proc/kmsg allows:
|
||||
- open (SYSLOG_ACTION_OPEN) if CAP_SYSLOG since it uses a destructive
|
||||
single-reader interface (SYSLOG_ACTION_READ).
|
||||
- everything, after an open.
|
||||
|
||||
Fix this by reworking all of the access methods to use the
|
||||
check_syslog_permissions function and adding checks to devkmsg_open and
|
||||
devkmsg_read.
|
||||
- syslog syscall allows:
|
||||
- anything, if CAP_SYSLOG.
|
||||
- SYSLOG_ACTION_READ_ALL and SYSLOG_ACTION_SIZE_BUFFER, if dmesg_restrict==0.
|
||||
- nothing else (EPERM).
|
||||
|
||||
This fixes https://bugzilla.redhat.com/show_bug.cgi?id=903192
|
||||
The use-cases were:
|
||||
- dmesg(1) needs to do non-destructive SYSLOG_ACTION_READ_ALLs.
|
||||
- sysklog(1) needs to open /proc/kmsg, drop privs, and still issue the
|
||||
destructive SYSLOG_ACTION_READs.
|
||||
|
||||
AIUI, dmesg(1) is moving to /dev/kmsg, and systemd-journald doesn't
|
||||
clear the ring buffer.
|
||||
|
||||
Based on the comments in devkmsg_llseek, it sounds like actions besides
|
||||
reading aren't going to be supported by /dev/kmsg (i.e. SYSLOG_ACTION_CLEAR),
|
||||
so we have a strict subset of the non-destructive syslog syscall actions.
|
||||
|
||||
To this end, move the check as Josh had done, but also rename the constants
|
||||
to reflect their new uses (SYSLOG_FROM_CALL becomes SYSLOG_FROM_READER, and
|
||||
SYSLOG_FROM_FILE becomes SYSLOG_FROM_PROC). SYSLOG_FROM_READER allows
|
||||
non-destructive actions, and SYSLOG_FROM_PROC allows destructive actions
|
||||
after a capabilities-constrained SYSLOG_ACTION_OPEN check.
|
||||
|
||||
- /dev/kmsg allows:
|
||||
- open if CAP_SYSLOG or dmesg_restrict==0
|
||||
- reading/polling, after open
|
||||
|
||||
Signed-off-by: Kees Cook <keescook@chromium.org>
|
||||
Reported-by: Christian Kujau <lists@nerdbynature.de>
|
||||
CC: stable@vger.kernel.org
|
||||
Signed-off-by: Eric Paris <eparis@redhat.com>
|
||||
Signed-off-by: Josh Boyer <jwboyer@redhat.com>
|
||||
Cc: Josh Boyer <jwboyer@redhat.com>
|
||||
Cc: Kay Sievers <kay@vrfy.org>
|
||||
Cc: stable@vger.kernel.org
|
||||
---
|
||||
kernel/printk.c | 91 +++++++++++++++++++++++++++++----------------------------
|
||||
1 file changed, 47 insertions(+), 44 deletions(-)
|
||||
fs/proc/kmsg.c | 10 +++---
|
||||
include/linux/syslog.h | 4 +--
|
||||
kernel/printk.c | 91 ++++++++++++++++++++++++++----------------------
|
||||
3 files changed, 57 insertions(+), 48 deletions(-)
|
||||
|
||||
diff --git a/fs/proc/kmsg.c b/fs/proc/kmsg.c
|
||||
index bd4b5a7..bdfabda 100644
|
||||
--- a/fs/proc/kmsg.c
|
||||
+++ b/fs/proc/kmsg.c
|
||||
@@ -21,12 +21,12 @@ extern wait_queue_head_t log_wait;
|
||||
|
||||
static int kmsg_open(struct inode * inode, struct file * file)
|
||||
{
|
||||
- return do_syslog(SYSLOG_ACTION_OPEN, NULL, 0, SYSLOG_FROM_FILE);
|
||||
+ return do_syslog(SYSLOG_ACTION_OPEN, NULL, 0, SYSLOG_FROM_PROC);
|
||||
}
|
||||
|
||||
static int kmsg_release(struct inode * inode, struct file * file)
|
||||
{
|
||||
- (void) do_syslog(SYSLOG_ACTION_CLOSE, NULL, 0, SYSLOG_FROM_FILE);
|
||||
+ (void) do_syslog(SYSLOG_ACTION_CLOSE, NULL, 0, SYSLOG_FROM_PROC);
|
||||
return 0;
|
||||
}
|
||||
|
||||
@@ -34,15 +34,15 @@ static ssize_t kmsg_read(struct file *file, char __user *buf,
|
||||
size_t count, loff_t *ppos)
|
||||
{
|
||||
if ((file->f_flags & O_NONBLOCK) &&
|
||||
- !do_syslog(SYSLOG_ACTION_SIZE_UNREAD, NULL, 0, SYSLOG_FROM_FILE))
|
||||
+ !do_syslog(SYSLOG_ACTION_SIZE_UNREAD, NULL, 0, SYSLOG_FROM_PROC))
|
||||
return -EAGAIN;
|
||||
- return do_syslog(SYSLOG_ACTION_READ, buf, count, SYSLOG_FROM_FILE);
|
||||
+ return do_syslog(SYSLOG_ACTION_READ, buf, count, SYSLOG_FROM_PROC);
|
||||
}
|
||||
|
||||
static unsigned int kmsg_poll(struct file *file, poll_table *wait)
|
||||
{
|
||||
poll_wait(file, &log_wait, wait);
|
||||
- if (do_syslog(SYSLOG_ACTION_SIZE_UNREAD, NULL, 0, SYSLOG_FROM_FILE))
|
||||
+ if (do_syslog(SYSLOG_ACTION_SIZE_UNREAD, NULL, 0, SYSLOG_FROM_PROC))
|
||||
return POLLIN | POLLRDNORM;
|
||||
return 0;
|
||||
}
|
||||
diff --git a/include/linux/syslog.h b/include/linux/syslog.h
|
||||
index 3891139..98a3153 100644
|
||||
--- a/include/linux/syslog.h
|
||||
+++ b/include/linux/syslog.h
|
||||
@@ -44,8 +44,8 @@
|
||||
/* Return size of the log buffer */
|
||||
#define SYSLOG_ACTION_SIZE_BUFFER 10
|
||||
|
||||
-#define SYSLOG_FROM_CALL 0
|
||||
-#define SYSLOG_FROM_FILE 1
|
||||
+#define SYSLOG_FROM_READER 0
|
||||
+#define SYSLOG_FROM_PROC 1
|
||||
|
||||
int do_syslog(int type, char __user *buf, int count, bool from_file);
|
||||
|
||||
diff --git a/kernel/printk.c b/kernel/printk.c
|
||||
index abbdd9e..5541095 100644
|
||||
index abbdd9e..53b5c5e 100644
|
||||
--- a/kernel/printk.c
|
||||
+++ b/kernel/printk.c
|
||||
@@ -368,6 +368,46 @@ static void log_store(int facility, int level,
|
||||
@@ -368,6 +368,53 @@ static void log_store(int facility, int level,
|
||||
log_next_seq++;
|
||||
}
|
||||
|
||||
|
|
@ -41,8 +114,12 @@ index abbdd9e..5541095 100644
|
|||
+{
|
||||
+ if (dmesg_restrict)
|
||||
+ return 1;
|
||||
+ /* Unless restricted, we allow "read all" and "get buffer size" for everybody */
|
||||
+ return type != SYSLOG_ACTION_READ_ALL && type != SYSLOG_ACTION_SIZE_BUFFER;
|
||||
+ /*
|
||||
+ * Unless restricted, we allow "read all" and "get buffer size"
|
||||
+ * for everybody.
|
||||
+ */
|
||||
+ return type != SYSLOG_ACTION_READ_ALL &&
|
||||
+ type != SYSLOG_ACTION_SIZE_BUFFER;
|
||||
+}
|
||||
+
|
||||
+static int check_syslog_permissions(int type, bool from_file)
|
||||
|
|
@ -52,55 +129,42 @@ index abbdd9e..5541095 100644
|
|||
+ * already done the capabilities checks at open time.
|
||||
+ */
|
||||
+ if (from_file && type != SYSLOG_ACTION_OPEN)
|
||||
+ goto ok;
|
||||
+ return 0;
|
||||
+
|
||||
+ if (syslog_action_restricted(type)) {
|
||||
+ if (capable(CAP_SYSLOG))
|
||||
+ goto ok;
|
||||
+ /* For historical reasons, accept CAP_SYS_ADMIN too, with a warning */
|
||||
+ return 0;
|
||||
+ /*
|
||||
+ * For historical reasons, accept CAP_SYS_ADMIN too, with
|
||||
+ * a warning.
|
||||
+ */
|
||||
+ if (capable(CAP_SYS_ADMIN)) {
|
||||
+ printk_once(KERN_WARNING "%s (%d): "
|
||||
+ "Attempt to access syslog with CAP_SYS_ADMIN "
|
||||
+ "but no CAP_SYSLOG (deprecated).\n",
|
||||
+ current->comm, task_pid_nr(current));
|
||||
+ goto ok;
|
||||
+ return 0;
|
||||
+ }
|
||||
+ return -EPERM;
|
||||
+ }
|
||||
+ok:
|
||||
+ return security_syslog(type);
|
||||
+}
|
||||
+
|
||||
+
|
||||
/* /dev/kmsg - userspace message inject/listen interface */
|
||||
struct devkmsg_user {
|
||||
u64 seq;
|
||||
@@ -443,10 +483,16 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
|
||||
char cont = '-';
|
||||
size_t len;
|
||||
ssize_t ret;
|
||||
+ int err;
|
||||
|
||||
if (!user)
|
||||
return -EBADF;
|
||||
|
||||
+ err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
|
||||
+ SYSLOG_FROM_FILE);
|
||||
+ if (err)
|
||||
+ return err;
|
||||
+
|
||||
ret = mutex_lock_interruptible(&user->lock);
|
||||
if (ret)
|
||||
return ret;
|
||||
@@ -624,7 +670,7 @@ static int devkmsg_open(struct inode *inode, struct file *file)
|
||||
@@ -624,7 +671,8 @@ static int devkmsg_open(struct inode *inode, struct file *file)
|
||||
if ((file->f_flags & O_ACCMODE) == O_WRONLY)
|
||||
return 0;
|
||||
|
||||
- err = security_syslog(SYSLOG_ACTION_READ_ALL);
|
||||
+ err = check_syslog_permissions(SYSLOG_ACTION_OPEN, SYSLOG_FROM_FILE);
|
||||
+ err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
|
||||
+ SYSLOG_FROM_READER);
|
||||
if (err)
|
||||
return err;
|
||||
|
||||
@@ -817,45 +863,6 @@ static inline void boot_delay_msec(int level)
|
||||
@@ -817,45 +865,6 @@ static inline void boot_delay_msec(int level)
|
||||
}
|
||||
#endif
|
||||
|
||||
|
|
@ -146,17 +210,19 @@ index abbdd9e..5541095 100644
|
|||
#if defined(CONFIG_PRINTK_TIME)
|
||||
static bool printk_time = 1;
|
||||
#else
|
||||
@@ -1131,10 +1138,6 @@ int do_syslog(int type, char __user *buf, int len, bool from_file)
|
||||
if (error)
|
||||
goto out;
|
||||
@@ -1253,7 +1262,7 @@ out:
|
||||
|
||||
- error = security_syslog(type);
|
||||
- if (error)
|
||||
- return error;
|
||||
-
|
||||
switch (type) {
|
||||
case SYSLOG_ACTION_CLOSE: /* Close log */
|
||||
break;
|
||||
SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
|
||||
{
|
||||
- return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
|
||||
+ return do_syslog(type, buf, len, SYSLOG_FROM_READER);
|
||||
}
|
||||
|
||||
/*
|
||||
--
|
||||
1.8.1.4
|
||||
1.7.9.5
|
||||
|
||||
|
||||
--
|
||||
Kees Cook
|
||||
Chrome OS Security
|
||||
|
|
|
|||
|
|
@ -2356,6 +2356,9 @@ fi
|
|||
# '-' | |
|
||||
# '-'
|
||||
%changelog
|
||||
* Tue May 07 2013 Josh Boyer <jwboyer@redhat.com>
|
||||
- Fix dmesg_restrict patch to avoid regression (rhbz 952655)
|
||||
|
||||
* Wed May 01 2013 Justin M. Forbes <jforbes@redhat.com> - 3.8.11-100
|
||||
- Linux v3.8.11
|
||||
|
||||
|
|
|
|||
Loading…
Reference in New Issue