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ceph: fix bounds check in ceph_decode_need and ceph_encode_need 

Given a large n, the bounds check (*p + n > end) can be bypassed due to
pointer wraparound.  A safer check is (n > end - *p).

[elder@dreamhost.com: inverted test and renamed ceph_has_room()]

Signed-off-by: Xi Wang <xi.wang@gmail.com>
Reviewed-by: Alex Elder <elder@dreamhost.com>
This commit is contained in:
Xi Wang 2012-04-20 15:49:44 -05:00 committed by Alex Elder
parent 065a68f916
commit 76aa542fb9
1 changed files with 7 additions and 2 deletions
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9
include/linux/ceph/decode.h
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@ -45,9 +45,14 @@ static inline void ceph_decode_copy(void **p, void *pv, size_t n)
/*
* bounds check input.
*/
static inline int ceph_has_room(void **p, void *end, size_t n)
{
return end >= *p && n <= end - *p;
}
#define ceph_decode_need(p, end, n, bad) \
do { \
if (unlikely(*(p) + (n) > (end))) \
if (!likely(ceph_has_room(p, end, n))) \
goto bad; \
} while (0)
@ -166,7 +171,7 @@ static inline void ceph_encode_string(void **p, void *end,
#define ceph_encode_need(p, end, n, bad) \
do { \
if (unlikely(*(p) + (n) > (end))) \
if (!likely(ceph_has_room(p, end, n))) \
goto bad; \
} while (0)