linux-kernel - [PATCH] net/rds: Avoid potential use after free in rds_send_remove_from

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Date:   Tue,  6 Apr 2021 19:09:12 -0500
From:   Aditya Pakki <pakki001@....edu>
To:     pakki001@....edu
Cc:     Santosh Shilimkar <santosh.shilimkar@...cle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        linux-rdma@...r.kernel.org, rds-devel@....oracle.com,
        linux-kernel@...r.kernel.org
Subject: [PATCH] net/rds: Avoid potential use after free in rds_send_remove_from_sock

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@....edu>
---
 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 071a261fdaab..90ebcfe5fe3b 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 985d0b7713ac..fe5264b9d4b3 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);
 	}
 
-- 
2.25.1