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235b42b586
IPv6 input attaches a non-refcounted (NOREF) dst to skbs under RCU.
When an ingress multicast packet misses MFC lookup,
ip6mr_cache_unresolved() places the skb onto the unresolved queue,
escaping the receive-side RCU grace period.
If the underlying route is deleted and freed, and the MFC queue is later
resolved with a wrong parent interface, ip6_mr_forward() invokes
ip6mr_cache_report(..., MRT6MSG_WRONGMIF), which executes
dst_clone(skb_dst(pkt)) on the freed dst entry, triggering a slab
use-after-free.
Report packets queued to mroute6_sk (a raw socket) and netlink
notifications do not require an attached dst entry.
Fix this by:
1. Removing dst_clone() in ip6mr_cache_report() and ensuring report skbs
do not hold a dst.
2. Dropping skb_dst before queuing unresolved skbs in
ip6mr_cache_unresolved(), matching the fact that multicast
forwarding resolves outgoing routes anew via ip6_route_output().
Fixes: 67f415dd29 ("ipv6: convert rx data path to not take refcnt on dst")
Reported-by: Zero Day Initiative <zdi-disclosures@trendmicro.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Hangbin Liu <liuhangbin@kylinos.cn>
Link: https://patch.msgid.link/20260818172755.4083692-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2832 lines
67 KiB
2832 lines
67 KiB