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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 9/17/26 12:19, Ryan Lee wrote: > On Thu, Sep 17, 2026 at 11:59 AM Wentao Liang wrote: >> >> The inner block in aa_unix_file_perm() re-declares plabel, shadowing the >> outer variable that is released at the out label. The reference taken by >> aa_get_label_rcu() is thus lost when the block exits, and aa_put_label() >> at out is a no-op on the still NULL outer plabel, leaking one label per >> permission check on a non-filesystem unix socket. >> >> Drop the shadowing declaration so the outer plabel is used and released. >> >> Fixes: 88fec3526e84 ("apparmor: make sure unix socket labeling is correctly updated.") >> Cc: stable@vger.kernel.org >> Signed-off-by: Wentao Liang >> --- >> security/apparmor/af_unix.c | 1 - >> 1 file changed, 1 deletion(-) >> >> diff --git a/security/apparmor/af_unix.c b/security/apparmor/af_unix.c >> index fdb4a9f212c3..ecb40cfe7e14 100644 >> --- a/security/apparmor/af_unix.c >> +++ b/security/apparmor/af_unix.c >> @@ -758,7 +758,6 @@ int aa_unix_file_perm(const struct cred *subj_cred, struct aa_label *label, >> unix_fs_perm(op, request, subj_cred, label, >> is_unix_fs(peer_sk) ? &peer_path : NULL)); >> } else if (!is_sk_fs) { >> - struct aa_label *plabel; >> struct aa_sk_ctx *pctx = aa_sock(peer_sk); >> >> rcu_read_lock(); >> -- >> 2.34.1 >> >> > > NACK: this exact patch has been proposed before, and unfortunately > exposes an additional latent bug around plabel handling that results > in a use-after-free if the shadowed declaration is removed without > additional fixes. > > I can try to dig out the relevant exchange from the AppArmor mailing > list later, if you'd be interested. > The series Ryan is referring to is in Linus's tree, so you should see the fix rolling out to stable kernels as well soon. 6d25e7b47616c apparmor: fix refcount leak when updating the sk_ctx b1aea2c196077 apparmor: fix race in unix socket mediation when peer_path is used 4483efe4f2151 apparmor: fix shadowing of plabel that prevents cache from being updated > Ryan