From: Allison Henderson allison.henderson@oracle.com

commit f1acf1ac84d2ae97b7889b87223c1064df850069 upstream.

Functions rds_still_queued and rds_clear_recv_queue lock a given socket in order to safely iterate over the incoming rds messages. However calling rds_inc_put while under this lock creates a potential deadlock. rds_inc_put may eventually call rds_message_purge, which will lock m_rs_lock. This is the incorrect locking order since m_rs_lock is meant to be locked before the socket. To fix this, we move the message item to a local list or variable that wont need rs_recv_lock protection. Then we can safely call rds_inc_put on any item stored locally after rs_recv_lock is released.

Fixes: bdbe6fbc6a2f ("RDS: recv.c") Reported-by: syzbot+f9db6ff27b9bfdcfeca0@syzkaller.appspotmail.com Reported-by: syzbot+dcd73ff9291e6d34b3ab@syzkaller.appspotmail.com Signed-off-by: Allison Henderson allison.henderson@oracle.com Link: https://lore.kernel.org/r/20240209022854.200292-1-allison.henderson@oracle.c... Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Denis Rastyogin gerben@altlinux.org --- net/rds/recv.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/net/rds/recv.c b/net/rds/recv.c index 967d115f97ef..f570d64367a4 100644 --- a/net/rds/recv.c +++ b/net/rds/recv.c @@ -424,6 +424,7 @@ static int rds_still_queued(struct rds_sock *rs, struct rds_incoming *inc, struct sock *sk = rds_rs_to_sk(rs); int ret = 0; unsigned long flags; + struct rds_incoming *to_drop = NULL;

write_lock_irqsave(&rs->rs_recv_lock, flags); if (!list_empty(&inc->i_item)) { @@ -434,11 +435,14 @@ static int rds_still_queued(struct rds_sock *rs, struct rds_incoming *inc, -be32_to_cpu(inc->i_hdr.h_len), inc->i_hdr.h_dport); list_del_init(&inc->i_item); - rds_inc_put(inc); + to_drop = inc; } } write_unlock_irqrestore(&rs->rs_recv_lock, flags);

+ if (to_drop) + rds_inc_put(to_drop); + rdsdebug("inc %p rs %p still %d dropped %d\n", inc, rs, ret, drop); return ret; } @@ -761,16 +765,21 @@ void rds_clear_recv_queue(struct rds_sock *rs) struct sock *sk = rds_rs_to_sk(rs); struct rds_incoming *inc, *tmp; unsigned long flags; + LIST_HEAD(to_drop);

write_lock_irqsave(&rs->rs_recv_lock, flags); list_for_each_entry_safe(inc, tmp, &rs->rs_recv_queue, i_item) { rds_recv_rcvbuf_delta(rs, sk, inc->i_conn->c_lcong, -be32_to_cpu(inc->i_hdr.h_len), inc->i_hdr.h_dport); + list_move(&inc->i_item, &to_drop); + } + write_unlock_irqrestore(&rs->rs_recv_lock, flags); + + list_for_each_entry_safe(inc, tmp, &to_drop, i_item) { list_del_init(&inc->i_item); rds_inc_put(inc); } - write_unlock_irqrestore(&rs->rs_recv_lock, flags); }

/*