3.16.78-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet edumazet@google.com
commit 32d3182cd2cd29b2e7e04df7b0db350fbe11289f upstream.
packet_sendmsg() checks tx_ring.pg_vec to decide if it must call tpacket_snd().
Problem is that the check is lockless, meaning another thread can issue a concurrent setsockopt(PACKET_TX_RING ) to flip tx_ring.pg_vec back to NULL.
Given that tpacket_snd() grabs pg_vec_lock mutex, we can perform the check again to solve the race.
syzbot reported :
kasan: CONFIG_KASAN_INLINE enabled kasan: GPF could be caused by NULL-ptr deref or user memory access general protection fault: 0000 [#1] PREEMPT SMP KASAN CPU: 1 PID: 11429 Comm: syz-executor394 Not tainted 5.3.0-rc4+ #101 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:packet_lookup_frame+0x8d/0x270 net/packet/af_packet.c:474 Code: c1 ee 03 f7 73 0c 80 3c 0e 00 0f 85 cb 01 00 00 48 8b 0b 89 c0 4c 8d 24 c1 48 b8 00 00 00 00 00 fc ff df 4c 89 e1 48 c1 e9 03 <80> 3c 01 00 0f 85 94 01 00 00 48 8d 7b 10 4d 8b 3c 24 48 b8 00 00 RSP: 0018:ffff88809f82f7b8 EFLAGS: 00010246 RAX: dffffc0000000000 RBX: ffff8880a45c7030 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 1ffff110148b8e06 RDI: ffff8880a45c703c RBP: ffff88809f82f7e8 R08: ffff888087aea200 R09: fffffbfff134ae50 R10: fffffbfff134ae4f R11: ffffffff89a5727f R12: 0000000000000000 R13: 0000000000000001 R14: ffff8880a45c6ac0 R15: 0000000000000000 FS: 00007fa04716f700(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fa04716edb8 CR3: 0000000091eb4000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: packet_current_frame net/packet/af_packet.c:487 [inline] tpacket_snd net/packet/af_packet.c:2667 [inline] packet_sendmsg+0x590/0x6250 net/packet/af_packet.c:2975 sock_sendmsg_nosec net/socket.c:637 [inline] sock_sendmsg+0xd7/0x130 net/socket.c:657 ___sys_sendmsg+0x3e2/0x920 net/socket.c:2311 __sys_sendmmsg+0x1bf/0x4d0 net/socket.c:2413 __do_sys_sendmmsg net/socket.c:2442 [inline] __se_sys_sendmmsg net/socket.c:2439 [inline] __x64_sys_sendmmsg+0x9d/0x100 net/socket.c:2439 do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe
Fixes: 69e3c75f4d54 ("net: TX_RING and packet mmap") Signed-off-by: Eric Dumazet edumazet@google.com Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Ben Hutchings ben@decadent.org.uk --- net/packet/af_packet.c | 7 +++++++ 1 file changed, 7 insertions(+)
--- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -2286,6 +2286,13 @@ static int tpacket_snd(struct packet_soc
mutex_lock(&po->pg_vec_lock);
+ /* packet_sendmsg() check on tx_ring.pg_vec was lockless, + * we need to confirm it under protection of pg_vec_lock. + */ + if (unlikely(!po->tx_ring.pg_vec)) { + err = -EBUSY; + goto out; + } if (likely(saddr == NULL)) { dev = packet_cached_dev_get(po); proto = po->num;