From: Xi Wang Date: Tue, 29 Nov 2011 09:26:30 +0000 (+0000) Subject: sctp: better integer overflow check in sctp_auth_create_key() X-Git-Tag: v3.2-rc5~56^2~16 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=c89304b8ea34ab48ba6ae10e06a8b1b8c8212307;p=profile%2Fivi%2Fkernel-x86-ivi.git 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 Cc: Vlad Yasevich Signed-off-by: David S. Miller --- diff --git a/net/sctp/auth.c b/net/sctp/auth.c index 865e68f..bf81204 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 */