From: Cen Zhang (Microsoft) Date: Sun, 19 Jul 2026 21:03:57 +0000 (-0400) Subject: rds: tcp: unregister sysctl before tearing down listen socket X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=167e54c703ccd4fa028feb568b0d1002020cff86;p=thirdparty%2Fkernel%2Flinux.git 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 Signed-off-by: Cen Zhang (Microsoft) Link: https://patch.msgid.link/20260719210357.10179-1-blbllhy@gmail.com Signed-off-by: Jakub Kicinski --- 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 = {