next_pidmap: fix overflow condition
authorLinus Torvalds <torvalds@linux-foundation.org>
Mon, 18 Apr 2011 17:35:30 +0000 (10:35 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Mon, 18 Apr 2011 17:35:30 +0000 (10:35 -0700)
commitc78193e9c7bcbf25b8237ad0dec82f805c4ea69b
tree1d0c3c90770acb003af06d727b794eb002d58ec7
parenta1b49cb7e2a7961ec3aa8b64860bf480d4ec9077
next_pidmap: fix overflow condition

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>
include/linux/pid.h
kernel/pid.c