Commit 167e54c703cc for kernel

commit 167e54c703ccd4fa028feb568b0d1002020cff86
Author: Cen Zhang (Microsoft) <blbllhy@gmail.com>
Date:   Sun Jul 19 17:03:57 2026 -0400

    rds: tcp: unregister sysctl before tearing down listen socket

    rds_tcp_exit_net() frees the per-netns RDS TCP listen socket via
    rds_tcp_kill_sock() before unregistering the per-netns sysctl table.  Since
    rds_tcp_skbuf_handler() derives the netns from
    rtn->rds_tcp_listen_sock->sk, a concurrent sysctl write can race with
    netns teardown and dereference the freed socket/sk.

    KASAN reports the race as:

      BUG: KASAN: slab-use-after-free in rds_tcp_skbuf_handler+0x2aa/0x2e0
      rds_tcp_skbuf_handler              net/rds/tcp.c:721
      proc_sys_call_handler              fs/proc/proc_sysctl.c
      vfs_write                          fs/read_write.c
      __x64_sys_pwrite64                 fs/read_write.c

    Fix this by unregistering the RDS TCP sysctl table before calling
    rds_tcp_kill_sock().  unregister_net_sysctl_table() prevents new sysctl
    handlers from starting and waits for in-flight handlers to finish, so
    the listen socket can then be released safely. The fix was tested
    against the linked reproducer.

    Fixes: 7f5611cbc487 ("rds: sysctl: rds_tcp_{rcv,snd}buf: avoid using current->nsproxy")
    Reported-by: AutonomousCodeSecurity@microsoft.com
    Link: https://lore.kernel.org/all/20260719203718.9680-1-blbllhy@gmail.com
    Reviewed-by: Allison Henderson <achender@kernel.org>
    Signed-off-by: Cen Zhang (Microsoft) <blbllhy@gmail.com>
    Link: https://patch.msgid.link/20260719210357.10179-1-blbllhy@gmail.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/rds/tcp.c b/net/rds/tcp.c
index 955d92277d5a..5de35d556f29 100644
--- a/net/rds/tcp.c
+++ b/net/rds/tcp.c
@@ -657,13 +657,13 @@ static void __net_exit rds_tcp_exit_net(struct net *net)
 {
 	struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid);

-	rds_tcp_kill_sock(net);
-
 	if (rtn->rds_tcp_sysctl)
 		unregister_net_sysctl_table(rtn->rds_tcp_sysctl);

 	if (net != &init_net)
 		kfree(rtn->ctl_table);
+
+	rds_tcp_kill_sock(net);
 }

 static struct pernet_operations rds_tcp_net_ops = {