diff options
| author | Linus Torvalds <torvalds@linux-foundation.org> | 2011-04-18 10:35:30 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2011-04-21 14:32:52 -0700 |
| commit | c8b265db1e63fdb296ec2721f5c1473c44bc4dc5 (patch) | |
| tree | ef932aa910796d144dbe99a85d2d9123167c8705 | |
| parent | dd8eece9b71a865b6f223c2f84058788870cd655 (diff) | |
| download | lwn-c8b265db1e63fdb296ec2721f5c1473c44bc4dc5.tar.gz lwn-c8b265db1e63fdb296ec2721f5c1473c44bc4dc5.zip | |
next_pidmap: fix overflow condition
commit c78193e9c7bcbf25b8237ad0dec82f805c4ea69b upstream.
next_pidmap() just quietly accepted whatever 'last' pid that was passed
in, which is not all that safe when one of the users is /proc.
Admittedly the proc code should do some sanity checking on the range
(and that will be the next commit), but that doesn't mean that the
helper functions should just do that pidmap pointer arithmetic without
checking the range of its arguments.
So clamp 'last' to PID_MAX_LIMIT. The fact that we then do "last+1"
doesn't really matter, the for-loop does check against the end of the
pidmap array properly (it's only the actual pointer arithmetic overflow
case we need to worry about, and going one bit beyond isn't going to
overflow).
[ Use PID_MAX_LIMIT rather than pid_max as per Eric Biederman ]
Reported-by: Tavis Ormandy <taviso@cmpxchg8b.com>
Analyzed-by: Robert Święcki <robert@swiecki.net>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| -rw-r--r-- | include/linux/pid.h | 2 | ||||
| -rw-r--r-- | kernel/pid.c | 5 |
2 files changed, 5 insertions, 2 deletions
diff --git a/include/linux/pid.h b/include/linux/pid.h index 49f1c2f66e95..ec9f2df57f1b 100644 --- a/include/linux/pid.h +++ b/include/linux/pid.h @@ -117,7 +117,7 @@ extern struct pid *find_vpid(int nr); */ extern struct pid *find_get_pid(int nr); extern struct pid *find_ge_pid(int nr, struct pid_namespace *); -int next_pidmap(struct pid_namespace *pid_ns, int last); +int next_pidmap(struct pid_namespace *pid_ns, unsigned int last); extern struct pid *alloc_pid(struct pid_namespace *ns); extern void free_pid(struct pid *pid); diff --git a/kernel/pid.c b/kernel/pid.c index 39b65b69584f..6aeebc20d34b 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -217,11 +217,14 @@ static int alloc_pidmap(struct pid_namespace *pid_ns) return -1; } -int next_pidmap(struct pid_namespace *pid_ns, int last) +int next_pidmap(struct pid_namespace *pid_ns, unsigned int last) { int offset; struct pidmap *map, *end; + if (last >= PID_MAX_LIMIT) + return -1; + offset = (last + 1) & BITS_PER_PAGE_MASK; map = &pid_ns->pidmap[(last + 1)/BITS_PER_PAGE]; end = &pid_ns->pidmap[PIDMAP_ENTRIES]; |