5.4-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
[ Upstream commit 77ee7a6d16b6ec07b5c3ae2b6b60a24c1afbed09 ]
Blamed commit forgot MSG_PEEK case, allowing a crash [1] as found by syzbot.
Rework vlan_get_tci() to not touch skb at all, so that it can be used from many cpus on the same skb.
Add a const qualifier to skb argument.
[1] skbuff: skb_under_panic: text:ffffffff8a8da482 len:32 put:14 head:ffff88807a1d5800 data:ffff88807a1d5810 tail:0x14 end:0x140 dev:<NULL> ------------[ cut here ]------------ kernel BUG at net/core/skbuff.c:206 ! Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI CPU: 0 UID: 0 PID: 5880 Comm: syz-executor172 Not tainted 6.13.0-rc3-syzkaller-00762-g9268abe611b0 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024 RIP: 0010:skb_panic net/core/skbuff.c:206 [inline] RIP: 0010:skb_under_panic+0x14b/0x150 net/core/skbuff.c:216 Code: 0b 8d 48 c7 c6 9e 6c 26 8e 48 8b 54 24 08 8b 0c 24 44 8b 44 24 04 4d 89 e9 50 41 54 41 57 41 56 e8 3a 5a 79 f7 48 83 c4 20 90 <0f> 0b 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 RSP: 0018:ffffc90003baf5b8 EFLAGS: 00010286 RAX: 0000000000000087 RBX: dffffc0000000000 RCX: 8565c1eec37aa000 RDX: 0000000000000000 RSI: 0000000080000000 RDI: 0000000000000000 RBP: ffff88802616fb50 R08: ffffffff817f0a4c R09: 1ffff92000775e50 R10: dffffc0000000000 R11: fffff52000775e51 R12: 0000000000000140 R13: ffff88807a1d5800 R14: ffff88807a1d5810 R15: 0000000000000014 FS: 00007fa03261f6c0(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007ffd65753000 CR3: 0000000031720000 CR4: 00000000003526f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> skb_push+0xe5/0x100 net/core/skbuff.c:2636 vlan_get_tci+0x272/0x550 net/packet/af_packet.c:565 packet_recvmsg+0x13c9/0x1ef0 net/packet/af_packet.c:3616 sock_recvmsg_nosec net/socket.c:1044 [inline] sock_recvmsg+0x22f/0x280 net/socket.c:1066 ____sys_recvmsg+0x1c6/0x480 net/socket.c:2814 ___sys_recvmsg net/socket.c:2856 [inline] do_recvmmsg+0x426/0xab0 net/socket.c:2951 __sys_recvmmsg net/socket.c:3025 [inline] __do_sys_recvmmsg net/socket.c:3048 [inline] __se_sys_recvmmsg net/socket.c:3041 [inline] __x64_sys_recvmmsg+0x199/0x250 net/socket.c:3041 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
Fixes: 79eecf631c14 ("af_packet: Handle outgoing VLAN packets without hardware offloading") Reported-by: syzbot+8400677f3fd43f37d3bc@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/6772c485.050a0220.2f3838.04c6.GAE@google.com/... Signed-off-by: Eric Dumazet edumazet@google.com Cc: Chengen Du chengen.du@canonical.com Reviewed-by: Willem de Bruijn willemb@google.com Link: https://patch.msgid.link/20241230161004.2681892-1-edumazet@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/packet/af_packet.c | 12 +++--------- 1 file changed, 3 insertions(+), 9 deletions(-)
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 88bc4a21dda4..4938926137b2 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -492,10 +492,8 @@ static void *packet_current_frame(struct packet_sock *po, return packet_lookup_frame(po, rb, rb->head, status); }
-static u16 vlan_get_tci(struct sk_buff *skb, struct net_device *dev) +static u16 vlan_get_tci(const struct sk_buff *skb, struct net_device *dev) { - u8 *skb_orig_data = skb->data; - int skb_orig_len = skb->len; struct vlan_hdr vhdr, *vh; unsigned int header_len;
@@ -516,12 +514,8 @@ static u16 vlan_get_tci(struct sk_buff *skb, struct net_device *dev) else return 0;
- skb_push(skb, skb->data - skb_mac_header(skb)); - vh = skb_header_pointer(skb, header_len, sizeof(vhdr), &vhdr); - if (skb_orig_data != skb->data) { - skb->data = skb_orig_data; - skb->len = skb_orig_len; - } + vh = skb_header_pointer(skb, skb_mac_offset(skb) + header_len, + sizeof(vhdr), &vhdr); if (unlikely(!vh)) return 0;