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authorXi Wang <xi.wang@gmail.com>2011-11-29 10:26:30 +0100
committerDavid S. Miller <davem@davemloft.net>2011-11-29 21:51:03 +0100
commitc89304b8ea34ab48ba6ae10e06a8b1b8c8212307 (patch)
treeef464824214e0e82b488664df25d1e9ebb9128b7 /net/sctp
parentMerge branch 'nf' of git://1984.lsi.us.es/net (diff)
downloadlinux-c89304b8ea34ab48ba6ae10e06a8b1b8c8212307.tar.xz
linux-c89304b8ea34ab48ba6ae10e06a8b1b8c8212307.zip
sctp: better integer overflow check in sctp_auth_create_key()
The check from commit 30c2235c is incomplete and cannot prevent cases like key_len = 0x80000000 (INT_MAX + 1). In that case, the left-hand side of the check (INT_MAX - key_len), which is unsigned, becomes 0xffffffff (UINT_MAX) and bypasses the check. However this shouldn't be a security issue. The function is called from the following two code paths: 1) setsockopt() 2) sctp_auth_asoc_set_secret() In case (1), sca_keylength is never going to exceed 65535 since it's bounded by a u16 from the user API. As such, the key length will never overflow. In case (2), sca_keylength is computed based on the user key (1 short) and 2 * key_vector (3 shorts) for a total of 7 * USHRT_MAX, which still will not overflow. In other words, this overflow check is not really necessary. Just make it more correct. Signed-off-by: Xi Wang <xi.wang@gmail.com> Cc: Vlad Yasevich <vladislav.yasevich@hp.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sctp')
-rw-r--r--net/sctp/auth.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/net/sctp/auth.c b/net/sctp/auth.c
index 865e68fef21c..bf812048cf6f 100644
--- a/net/sctp/auth.c
+++ b/net/sctp/auth.c
@@ -82,7 +82,7 @@ static struct sctp_auth_bytes *sctp_auth_create_key(__u32 key_len, gfp_t gfp)
struct sctp_auth_bytes *key;
/* Verify that we are not going to overflow INT_MAX */
- if ((INT_MAX - key_len) < sizeof(struct sctp_auth_bytes))
+ if (key_len > (INT_MAX - sizeof(struct sctp_auth_bytes)))
return NULL;
/* Allocate the shared key */