Re: [PATCH net] rds: tcp: fix uninit-value in __inet_bind
From: Charalampos Mitrodimas <hidden>
Date: 2026-02-15 17:41:28
Also in:
linux-rdma, lkml
Tabrez Ahmed [off-list ref] writes:
KMSAN reported an uninit-value access in __inet_bind() when binding an RDS TCP socket. The uninitialized memory originates from rds_tcp_conn_alloc(), which uses kmem_cache_alloc() to allocate the rds_tcp_connection structure. The structure is not zero-initialized, leaving random data in its fields. When the networking stack later tries to bind the socket using these dirty values, KMSAN flags the uninitialized access.
Most fields in rds_tcp_connection are explicitly initialized after allocation right? The only field actually read before being written is t_client_port_group. Could the description be more specific about which field is problematic?
Fix this by using kmem_cache_zalloc() instead of kmem_cache_alloc() to ensure the structure is zeroed out upon allocation. Reported-by: syzbot+aae646f09192f72a68dc@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=aae646f09192f72a68dc Tested-by: syzbot+aae646f09192f72a68dc@syzkaller.appspotmail.com Fixes: 70041088e3b9 ("RDS: Add TCP transport to RDS")
Not sure about this, the field trigger this bug, t_client_port_group,
did not exist in 70041088e3b9. It was introduced in
a20a6992558f ("net/rds: Encode cp_index in TCP source port")
which added both the field and the code in rds_tcp_conn_path_connect()
that reads it uninitialized:
if (++tc->t_client_port_group >= port_groups)
Should the Fixes that reference that instead? If I'm correct ofc.
Also, nit, commit message body should not exceed 75 characters.
Signed-off-by: Tabrez Ahmed <redacted> --- This is my first patch. Any feedback is appreciated!
Best of luck.
quoted hunk ↗ jump to hunk
net/rds/tcp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/net/rds/tcp.c b/net/rds/tcp.c index 45484a93d75f..04f310255692 100644 --- a/net/rds/tcp.c +++ b/net/rds/tcp.c@@ -373,7 +373,7 @@ static int rds_tcp_conn_alloc(struct rds_connection *conn, gfp_t gfp) int ret = 0; for (i = 0; i < RDS_MPATH_WORKERS; i++) { - tc = kmem_cache_alloc(rds_tcp_conn_slab, gfp); + tc = kmem_cache_zalloc(rds_tcp_conn_slab, gfp); if (!tc) { ret = -ENOMEM; goto fail;