net: openvswitch: conntrack: avoid modifying shared unconfirmed ct entry

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In a case where skb with an unconfirmed ct entry gets cloned, we may
end up committing both but with different sets of extensions.

The series of events:

 1. The first clone wants to commit and runs the helpers wiring up
    the extension pointer into the expectation list.
 2. Then it looses the confirmation keeping the entry unconfirmed.
 3. Second clone now wants to commit labels and adds the new extension
    for that breaking the pointer in the expectation list causing
    UAF on the destruction path later.

While this is possible to trigger, there should be no practical
network pipeline where committing both clones without modifications
into the same zone is needed.  So, let's just reset the entry in case
for some reason we got an skb with a shared one during commit.  This
doesn't affect any known use cases, but avoids any potential problems
with sharing and modification of the unconfirmed ct entry.

The fixes tag points to the introduction of helpers, since that's the
main UAF trigger for the sharing.

Fixes: cae3a26275 ("openvswitch: Allow attaching helpers to ct action")
Cc: stable@vger.kernel.org
Reported-by: Axel Mierczuk <axel.mierczuk@1password.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
Reviewed-by: Aaron Conole <aconole@redhat.com>
Link: https://patch.msgid.link/20260921145655.3167436-2-i.maximets@ovn.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

...

This commit is contained in:

Ilya Maximets 2026-09-21 16:55:43 +02:00 • committed by Jakub Kicinski

parent 33a61f0923

commit 26b2bd70d2

2 changed files with 17 additions and 0 deletions

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5

include/net/netfilter/nf_conntrack.h

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12

net/openvswitch/conntrack.c

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