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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</div>
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</head><body><pre style="font-family: sans-serif; font-size: 100%; white-space: pre-wrap; word-wrap: break-word">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>
---
v2:
- Add link to KASAN report and reproducer code.
- Add Reviewed-by tags.
net/rds/tcp.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/net/rds/tcp.c b/net/rds/tcp.c
index a1de114d5e2e..453d4077a85e 100644
--- a/net/rds/tcp.c
+++ b/net/rds/tcp.c
@@ -655,13 +655,13 @@ 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 = {
--
2.53.0
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