Re: [PATCH 6.1.y] bpf, sockmap: Fix race between element replace and close()

[Sasha Levin <sashal@kernel.org>]

[ Sasha's backport helper bot ]

Hi,

The upstream commit SHA1 provided is correct: ed1fc5d76b81a4d681211333c026202cad4d5649

WARNING: Author mismatch between patch and upstream commit:
Backport author: Alva Lan<alvalan9@foxmail.com>
Commit author: Michal Luczaj<mhal@rbox.co>


Status in newer kernel trees:
6.12.y | Present (different SHA1: bf2318e288f6)
6.6.y | Present (different SHA1: b015f19fedd2)
6.1.y | Present (different SHA1: b543d4a4153f)

Note: The patch differs from the upstream commit:
---
1:  ed1fc5d76b81 ! 1:  559c7465df3b bpf, sockmap: Fix race between element replace and close()
    @@ Metadata
      ## Commit message ##
         bpf, sockmap: Fix race between element replace and close()
     
    +    [ Upstream commit ed1fc5d76b81a4d681211333c026202cad4d5649 ]
    +
         Element replace (with a socket different from the one stored) may race
         with socket's close() link popping & unlinking. __sock_map_delete()
         unconditionally unrefs the (wrong) element:
    @@ Commit message
         Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
         Reviewed-by: John Fastabend <john.fastabend@gmail.com>
         Link: https://lore.kernel.org/bpf/20241202-sockmap-replace-v1-3-1e88579e7bd5@rbox.co
    +    Signed-off-by: Alva Lan <alvalan9@foxmail.com>
     
      ## net/core/sock_map.c ##
     @@ net/core/sock_map.c: static void *sock_map_lookup_sys(struct bpf_map *map, void *key)
    @@ net/core/sock_map.c: static void *sock_map_lookup_sys(struct bpf_map *map, void
     +	struct sock *sk = NULL;
      	int err = 0;
      
    - 	spin_lock_bh(&stab->lock);
    + 	if (irqs_disabled())
    + 		return -EOPNOTSUPP; /* locks here are hardirq-unsafe */
    + 
    + 	raw_spin_lock_bh(&stab->lock);
     -	sk = *psk;
     -	if (!sk_test || sk_test == sk)
    ++
     +	if (!sk_test || sk_test == *psk)
      		sk = xchg(psk, NULL);
      
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-6.1.y        |  Success    |  Success   |