From 40f0b1047918539f0b0f795ac65e35336b4c2c78 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 15 Jun 2026 09:02:37 +0000 Subject: [PATCH] xfrm: validate selector family and prefixlen during match syzbot reported a shift-out-of-bounds in xfrm_selector_match() due to AF_UNSPEC selector with large prefixlen (e.g. 128) matched against IPv4 flow (when XFRM_STATE_AF_UNSPEC is set). Fix this by: - Rejecting mismatched families in xfrm_selector_match. - Returning false in addr4_match if prefixlen > 32. - Returning false in addr_match if prefixlen > 128 (prevents overflow). Fixes: 3f0ab59e6537 ("xfrm: validate new SA's prefixlen using SA family when sel.family is unset") Reported-by: syzbot+9383b1ff0df4b29ca5e6@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/6a2fbe35.be3f099c.2836ae.0018.GAE@google.com/T/#u Signed-off-by: Eric Dumazet Signed-off-by: Steffen Klassert --- include/net/xfrm.h | 7 +++++++ net/xfrm/xfrm_policy.c | 3 +++ 2 files changed, 10 insertions(+) diff --git a/include/net/xfrm.h b/include/net/xfrm.h index 35a743129329..f8c909b0f0c3 100644 --- a/include/net/xfrm.h +++ b/include/net/xfrm.h @@ -943,6 +943,9 @@ static inline bool addr_match(const void *token1, const void *token2, unsigned int pdw; unsigned int pbi; + if (prefixlen > 128) + return false; + pdw = prefixlen >> 5; /* num of whole u32 in prefix */ pbi = prefixlen & 0x1f; /* num of bits in incomplete u32 in prefix */ @@ -967,6 +970,10 @@ static inline bool addr4_match(__be32 a1, __be32 a2, u8 prefixlen) /* C99 6.5.7 (3): u32 << 32 is undefined behaviour */ if (sizeof(long) == 4 && prefixlen == 0) return true; + + if (prefixlen > 32) + return false; + return !((a1 ^ a2) & htonl(~0UL << (32 - prefixlen))); } diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c index 1f4afd580105..639934f30016 100644 --- a/net/xfrm/xfrm_policy.c +++ b/net/xfrm/xfrm_policy.c @@ -242,6 +242,9 @@ __xfrm6_selector_match(const struct xfrm_selector *sel, const struct flowi *fl) bool xfrm_selector_match(const struct xfrm_selector *sel, const struct flowi *fl, unsigned short family) { + if (family != sel->family && sel->family != AF_UNSPEC) + return false; + switch (family) { case AF_INET: return __xfrm4_selector_match(sel, fl);