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authorLinus Torvalds <torvalds@linux-foundation.org>2011-04-18 10:35:30 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-04-18 10:35:30 -0700
commitc78193e9c7bcbf25b8237ad0dec82f805c4ea69b (patch)
tree1d0c3c90770acb003af06d727b794eb002d58ec7
parenta1b49cb7e2a7961ec3aa8b64860bf480d4ec9077 (diff)
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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>
-rw-r--r--include/linux/pid.h2
-rw-r--r--kernel/pid.c5
2 files changed, 5 insertions, 2 deletions
diff --git a/include/linux/pid.h b/include/linux/pid.h
index 31afb7ecbe1..cdced84261d 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 02f22127426..57a8346a270 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];