[PATCH AUTOSEL 5.4 35/39] net/rds: Avoid potential use after free in rds_send_remove_from_sock

[Sasha Levin]

From: Aditya Pakki <pakki001@xxxxxxx>

[ Upstream commit 0c85a7e87465f2d4cbc768e245f4f45b2f299b05 ]

In case of rs failure in rds_send_remove_from_sock(), the 'rm' resource
is freed and later under spinlock, causing potential use-after-free.
Set the free pointer to NULL to avoid undefined behavior.

Signed-off-by: Aditya Pakki <pakki001@xxxxxxx>
Acked-by: Santosh Shilimkar <santosh.shilimkar@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 net/rds/message.c | 1 +
 net/rds/send.c    | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/rds/message.c b/net/rds/message.c
index 2d43e13d6dd5..c3ecde854454 100644
--- a/net/rds/message.c
+++ b/net/rds/message.c
@@ -180,6 +180,7 @@ void rds_message_put(struct rds_message *rm)
 		rds_message_purge(rm);
 
 		kfree(rm);
+		rm = NULL;
 	}
 }
 EXPORT_SYMBOL_GPL(rds_message_put);
diff --git a/net/rds/send.c b/net/rds/send.c
index 68e2bdb08fd0..aa3bc081773f 100644
--- a/net/rds/send.c
+++ b/net/rds/send.c
@@ -665,7 +665,7 @@ static void rds_send_remove_from_sock(struct list_head *messages, int status)
 unlock_and_drop:
 		spin_unlock_irqrestore(&rm->m_rs_lock, flags);
 		rds_message_put(rm);
-		if (was_on_sock)
+		if (was_on_sock && rm)
 			rds_message_put(rm);
 	}
 
-- 
2.30.2