diff mbox series

[v2,net,3/3] ipv6: prevent possible UAF in ip6_xmit()

Message ID 20240820160859.3786976-4-edumazet@google.com (mailing list archive)
State Accepted
Commit 2d5ff7e339d04622d8282661df36151906d0e1c7
Delegated to: Netdev Maintainers
Headers show
Series ipv6: fix possible UAF in output paths | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag present in non-next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 16 this patch: 16
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers success CCed 6 of 6 maintainers
netdev/build_clang success Errors and warnings before: 16 this patch: 16
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success Fixes tag looks correct
netdev/build_allmodconfig_warn success Errors and warnings before: 16 this patch: 16
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 15 lines checked
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 3 this patch: 3
netdev/source_inline success Was 0 now: 0
netdev/contest success net-next-2024-08-20--18-00 (tests: 711)

Commit Message

Eric Dumazet Aug. 20, 2024, 4:08 p.m. UTC 
If skb_expand_head() returns NULL, skb has been freed
and the associated dst/idev could also have been freed.

We must use rcu_read_lock() to prevent a possible UAF.

Fixes: 0c9f227bee11 ("ipv6: use skb_expand_head in ip6_xmit")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Vasily Averin <vasily.averin@linux.dev>
---
 net/ipv6/ip6_output.c | 4 ++++
 1 file changed, 4 insertions(+)

Comments

David Ahern Aug. 20, 2024, 6:58 p.m. UTC | #1 
On 8/20/24 10:08 AM, Eric Dumazet wrote:
> If skb_expand_head() returns NULL, skb has been freed
> and the associated dst/idev could also have been freed.
> 
> We must use rcu_read_lock() to prevent a possible UAF.
> 
> Fixes: 0c9f227bee11 ("ipv6: use skb_expand_head in ip6_xmit")
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Cc: Vasily Averin <vasily.averin@linux.dev>
> ---
>  net/ipv6/ip6_output.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 

Reviewed-by: David Ahern <dsahern@kernel.org>
diff mbox series

Patch

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 1b9ebee7308f02a626c766de1794e6b114ae8554..f26841f1490f5c31e3b09bce5773391e779128e1 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -287,11 +287,15 @@  int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6,
 		head_room += opt->opt_nflen + opt->opt_flen;
 
 	if (unlikely(head_room > skb_headroom(skb))) {
+		/* Make sure idev stays alive */
+		rcu_read_lock();
 		skb = skb_expand_head(skb, head_room);
 		if (!skb) {
 			IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTDISCARDS);
+			rcu_read_unlock();
 			return -ENOBUFS;
 		}
+		rcu_read_unlock();
 	}
 
 	if (opt) {