Patch "sock_map: fix a NULL pointer dereference in sock_map_link_update_prog()" has been added to the 6.11-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    sock_map: fix a NULL pointer dereference in sock_map_link_update_prog()

to the 6.11-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     sock_map-fix-a-null-pointer-dereference-in-sock_map_.patch
and it can be found in the queue-6.11 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 58dbfe028aaf957aebbc0a0979a5a2c6b909404b
Author: Cong Wang <cong.wang@xxxxxxxxxxxxx>
Date:   Sat Oct 26 11:55:22 2024 -0700

    sock_map: fix a NULL pointer dereference in sock_map_link_update_prog()
    
    [ Upstream commit 740be3b9a6d73336f8c7d540842d0831dc7a808b ]
    
    The following race condition could trigger a NULL pointer dereference:
    
    sock_map_link_detach():         sock_map_link_update_prog():
       mutex_lock(&sockmap_mutex);
       ...
       sockmap_link->map = NULL;
       mutex_unlock(&sockmap_mutex);
                                       mutex_lock(&sockmap_mutex);
                                       ...
                                       sock_map_prog_link_lookup(sockmap_link->map);
                                       mutex_unlock(&sockmap_mutex);
       <continue>
    
    Fix it by adding a NULL pointer check. In this specific case, it makes
    no sense to update a link which is being released.
    
    Reported-by: Ruan Bonan <bonan.ruan@xxxxxxxxx>
    Fixes: 699c23f02c65 ("bpf: Add bpf_link support for sk_msg and sk_skb progs")
    Cc: Yonghong Song <yonghong.song@xxxxxxxxx>
    Cc: John Fastabend <john.fastabend@xxxxxxxxx>
    Cc: Jakub Sitnicki <jakub@xxxxxxxxxxxxxx>
    Signed-off-by: Cong Wang <cong.wang@xxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20241026185522.338562-1-xiyou.wangcong@xxxxxxxxx
    Signed-off-by: Martin KaFai Lau <martin.lau@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index 219fd8f1ca2a4..0550837775d5e 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -1771,6 +1771,10 @@ static int sock_map_link_update_prog(struct bpf_link *link,
 		ret = -EINVAL;
 		goto out;
 	}
+	if (!sockmap_link->map) {
+		ret = -ENOLINK;
+		goto out;
+	}
 
 	ret = sock_map_prog_link_lookup(sockmap_link->map, &pprog, &plink,
 					sockmap_link->attach_type);