From: Eric Dumazet edumazet@google.com
[ Upstream commit 0a182f8d607464911756b4dbef5d6cad8de22469 ]
sock_map_free() calls release_sock(sk) without owning a reference on the socket. This can cause use-after-free as syzbot found [1]
Jakub Sitnicki already took care of a similar issue in sock_hash_free() in commit 75e68e5bf2c7 ("bpf, sockhash: Synchronize delete from bucket list on map free")
[1] refcount_t: decrement hit 0; leaking memory. WARNING: CPU: 0 PID: 3785 at lib/refcount.c:31 refcount_warn_saturate+0x17c/0x1a0 lib/refcount.c:31 Modules linked in: CPU: 0 PID: 3785 Comm: kworker/u4:6 Not tainted 6.1.0-rc7-syzkaller-00103-gef4d3ea40565 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 Workqueue: events_unbound bpf_map_free_deferred RIP: 0010:refcount_warn_saturate+0x17c/0x1a0 lib/refcount.c:31 Code: 68 8b 31 c0 e8 75 71 15 fd 0f 0b e9 64 ff ff ff e8 d9 6e 4e fd c6 05 62 9c 3d 0a 01 48 c7 c7 80 bb 68 8b 31 c0 e8 54 71 15 fd <0f> 0b e9 43 ff ff ff 89 d9 80 e1 07 80 c1 03 38 c1 0f 8c a2 fe ff RSP: 0018:ffffc9000456fb60 EFLAGS: 00010246 RAX: eae59bab72dcd700 RBX: 0000000000000004 RCX: ffff8880207057c0 RDX: 0000000000000000 RSI: 0000000000000201 RDI: 0000000000000000 RBP: 0000000000000004 R08: ffffffff816fdabd R09: fffff520008adee5 R10: fffff520008adee5 R11: 1ffff920008adee4 R12: 0000000000000004 R13: dffffc0000000000 R14: ffff88807b1c6c00 R15: 1ffff1100f638dcf FS: 0000000000000000(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000001b30c30000 CR3: 000000000d08e000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> __refcount_dec include/linux/refcount.h:344 [inline] refcount_dec include/linux/refcount.h:359 [inline] __sock_put include/net/sock.h:779 [inline] tcp_release_cb+0x2d0/0x360 net/ipv4/tcp_output.c:1092 release_sock+0xaf/0x1c0 net/core/sock.c:3468 sock_map_free+0x219/0x2c0 net/core/sock_map.c:356 process_one_work+0x81c/0xd10 kernel/workqueue.c:2289 worker_thread+0xb14/0x1330 kernel/workqueue.c:2436 kthread+0x266/0x300 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306 </TASK>
Fixes: 7e81a3530206 ("bpf: Sockmap, ensure sock lock held during tear down") Signed-off-by: Eric Dumazet edumazet@google.com Reported-by: syzbot syzkaller@googlegroups.com Cc: Jakub Sitnicki jakub@cloudflare.com Cc: John Fastabend john.fastabend@gmail.com Cc: Alexei Starovoitov ast@kernel.org Cc: Daniel Borkmann daniel@iogearbox.net Cc: Song Liu songliubraving@fb.com Acked-by: John Fastabend john.fastabend@gmail.com Link: https://lore.kernel.org/r/20221202111640.2745533-1-edumazet@google.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/core/sock_map.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/net/core/sock_map.c b/net/core/sock_map.c index cbf4184fabc9..ee5d3f49b0b5 100644 --- a/net/core/sock_map.c +++ b/net/core/sock_map.c @@ -358,11 +358,13 @@ static void sock_map_free(struct bpf_map *map)
sk = xchg(psk, NULL); if (sk) { + sock_hold(sk); lock_sock(sk); rcu_read_lock(); sock_map_unref(sk, psk); rcu_read_unlock(); release_sock(sk); + sock_put(sk); } }