[PATCH AUTOSEL 4.9 21/23] net/rds: Avoid potential use after free in rds_send_remove_from_sock

[Sasha Levin]

From: Aditya Pakki <pakki...@umn.edu>

[ 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 <pakki...@umn.edu>
Acked-by: Santosh Shilimkar <santosh.shilim...@oracle.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
 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 6cb91061556a..bee84584ce34 100644
--- a/net/rds/message.c
+++ b/net/rds/message.c
@@ -90,6 +90,7 @@ 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 50241d30e16d..a84198e1b87c 100644
--- a/net/rds/send.c
+++ b/net/rds/send.c
@@ -640,7 +640,7 @@ 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