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author | John Fastabend <john.fastabend@gmail.com> | 2018-01-04 20:02:09 -0800 |
---|---|---|
committer | Daniel Borkmann <daniel@iogearbox.net> | 2018-01-07 00:01:46 +0100 |
commit | 5731a879d03bdaa00265f8ebc32dfd0e65d25276 (patch) | |
tree | 3a9d68d5c946353b0f0583e3440655e555826d60 /kernel | |
parent | 5133550296d43236439494aa955bfb765a89f615 (diff) | |
download | linux-5731a879d03bdaa00265f8ebc32dfd0e65d25276.tar.gz linux-5731a879d03bdaa00265f8ebc32dfd0e65d25276.tar.bz2 linux-5731a879d03bdaa00265f8ebc32dfd0e65d25276.zip |
bpf: sockmap missing NULL psock check
Add psock NULL check to handle a racing sock event that can get the
sk_callback_lock before this case but after xchg happens causing the
refcnt to hit zero and sock user data (psock) to be null and queued
for garbage collection.
Also add a comment in the code because this is a bit subtle and
not obvious in my opinion.
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/bpf/sockmap.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/kernel/bpf/sockmap.c b/kernel/bpf/sockmap.c index 5ee2e41893d9..1712d319c2d8 100644 --- a/kernel/bpf/sockmap.c +++ b/kernel/bpf/sockmap.c @@ -591,8 +591,15 @@ static void sock_map_free(struct bpf_map *map) write_lock_bh(&sock->sk_callback_lock); psock = smap_psock_sk(sock); - smap_list_remove(psock, &stab->sock_map[i]); - smap_release_sock(psock, sock); + /* This check handles a racing sock event that can get the + * sk_callback_lock before this case but after xchg happens + * causing the refcnt to hit zero and sock user data (psock) + * to be null and queued for garbage collection. + */ + if (likely(psock)) { + smap_list_remove(psock, &stab->sock_map[i]); + smap_release_sock(psock, sock); + } write_unlock_bh(&sock->sk_callback_lock); } rcu_read_unlock(); |