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authorEric Dumazet <edumazet@google.com>2022-01-31 18:23:58 -0800
committerJakub Kicinski <kuba@kernel.org>2022-02-01 20:21:10 -0800
commite42e70ad6ae2ae511a6143d2e8da929366e58bd9 (patch)
tree6de2e6b00a83cddc31fe8089aa93fa9b5df593cf /net/packet
parentc6f6f2444bdbe0079e41914a35081530d0409963 (diff)
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af_packet: fix data-race in packet_setsockopt / packet_setsockopt
When packet_setsockopt( PACKET_FANOUT_DATA ) reads po->fanout, no lock is held, meaning that another thread can change po->fanout. Given that po->fanout can only be set once during the socket lifetime (it is only cleared from fanout_release()), we can use READ_ONCE()/WRITE_ONCE() to document the race. BUG: KCSAN: data-race in packet_setsockopt / packet_setsockopt write to 0xffff88813ae8e300 of 8 bytes by task 14653 on cpu 0: fanout_add net/packet/af_packet.c:1791 [inline] packet_setsockopt+0x22fe/0x24a0 net/packet/af_packet.c:3931 __sys_setsockopt+0x209/0x2a0 net/socket.c:2180 __do_sys_setsockopt net/socket.c:2191 [inline] __se_sys_setsockopt net/socket.c:2188 [inline] __x64_sys_setsockopt+0x62/0x70 net/socket.c:2188 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae read to 0xffff88813ae8e300 of 8 bytes by task 14654 on cpu 1: packet_setsockopt+0x691/0x24a0 net/packet/af_packet.c:3935 __sys_setsockopt+0x209/0x2a0 net/socket.c:2180 __do_sys_setsockopt net/socket.c:2191 [inline] __se_sys_setsockopt net/socket.c:2188 [inline] __x64_sys_setsockopt+0x62/0x70 net/socket.c:2188 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae value changed: 0x0000000000000000 -> 0xffff888106f8c000 Reported by Kernel Concurrency Sanitizer on: CPU: 1 PID: 14654 Comm: syz-executor.3 Not tainted 5.16.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Fixes: 47dceb8ecdc1 ("packet: add classic BPF fanout mode") Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Willem de Bruijn <willemb@google.com> Reported-by: syzbot <syzkaller@googlegroups.com> Link: https://lore.kernel.org/r/20220201022358.330621-1-eric.dumazet@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/packet')
-rw-r--r--net/packet/af_packet.c8
1 files changed, 6 insertions, 2 deletions
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 85ea7ddb48db..ab87f22cc7ec 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1789,7 +1789,10 @@ static int fanout_add(struct sock *sk, struct fanout_args *args)
err = -ENOSPC;
if (refcount_read(&match->sk_ref) < match->max_num_members) {
__dev_remove_pack(&po->prot_hook);
- po->fanout = match;
+
+ /* Paired with packet_setsockopt(PACKET_FANOUT_DATA) */
+ WRITE_ONCE(po->fanout, match);
+
po->rollover = rollover;
rollover = NULL;
refcount_set(&match->sk_ref, refcount_read(&match->sk_ref) + 1);
@@ -3934,7 +3937,8 @@ packet_setsockopt(struct socket *sock, int level, int optname, sockptr_t optval,
}
case PACKET_FANOUT_DATA:
{
- if (!po->fanout)
+ /* Paired with the WRITE_ONCE() in fanout_add() */
+ if (!READ_ONCE(po->fanout))
return -EINVAL;
return fanout_set_data(po, optval, optlen);