linux/net/8021q
Eric Dumazet dacab578c7 vlan: fix a potential uninit-value in vlan_dev_hard_start_xmit()
syzbot triggered the following splat [1], sending an empty message
through pppoe_sendmsg().

When VLAN_FLAG_REORDER_HDR flag is set, vlan_dev_hard_header()
does not push extra bytes for the VLAN header, because vlan is offloaded.

Unfortunately vlan_dev_hard_start_xmit() first reads veth->h_vlan_proto
before testing (vlan->flags & VLAN_FLAG_REORDER_HDR).

We need to swap the two conditions.

[1]
BUG: KMSAN: uninit-value in vlan_dev_hard_start_xmit+0x171/0x7f0 net/8021q/vlan_dev.c:111
vlan_dev_hard_start_xmit+0x171/0x7f0 net/8021q/vlan_dev.c:111
__netdev_start_xmit include/linux/netdevice.h:4883 [inline]
netdev_start_xmit include/linux/netdevice.h:4897 [inline]
xmit_one net/core/dev.c:3580 [inline]
dev_hard_start_xmit+0x253/0xa20 net/core/dev.c:3596
__dev_queue_xmit+0x3c7f/0x5ac0 net/core/dev.c:4246
dev_queue_xmit include/linux/netdevice.h:3053 [inline]
pppoe_sendmsg+0xa93/0xb80 drivers/net/ppp/pppoe.c:900
sock_sendmsg_nosec net/socket.c:724 [inline]
sock_sendmsg net/socket.c:747 [inline]
____sys_sendmsg+0xa24/0xe40 net/socket.c:2501
___sys_sendmsg+0x2a1/0x3f0 net/socket.c:2555
__sys_sendmmsg+0x411/0xa50 net/socket.c:2641
__do_sys_sendmmsg net/socket.c:2670 [inline]
__se_sys_sendmmsg net/socket.c:2667 [inline]
__x64_sys_sendmmsg+0xbc/0x120 net/socket.c:2667
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Uninit was created at:
slab_post_alloc_hook+0x12d/0xb60 mm/slab.h:774
slab_alloc_node mm/slub.c:3452 [inline]
kmem_cache_alloc_node+0x543/0xab0 mm/slub.c:3497
kmalloc_reserve+0x148/0x470 net/core/skbuff.c:520
__alloc_skb+0x3a7/0x850 net/core/skbuff.c:606
alloc_skb include/linux/skbuff.h:1277 [inline]
sock_wmalloc+0xfe/0x1a0 net/core/sock.c:2583
pppoe_sendmsg+0x3af/0xb80 drivers/net/ppp/pppoe.c:867
sock_sendmsg_nosec net/socket.c:724 [inline]
sock_sendmsg net/socket.c:747 [inline]
____sys_sendmsg+0xa24/0xe40 net/socket.c:2501
___sys_sendmsg+0x2a1/0x3f0 net/socket.c:2555
__sys_sendmmsg+0x411/0xa50 net/socket.c:2641
__do_sys_sendmmsg net/socket.c:2670 [inline]
__se_sys_sendmmsg net/socket.c:2667 [inline]
__x64_sys_sendmmsg+0xbc/0x120 net/socket.c:2667
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

CPU: 0 PID: 29770 Comm: syz-executor.0 Not tainted 6.3.0-rc6-syzkaller-gc478e5b17829 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2023-05-17 12:55:39 +01:00
..
Kconfig treewide: replace '---help---' in Kconfig files with 'help' 2020-06-14 01:57:21 +09:00
Makefile net: remove blank lines at end of file 2018-07-24 14:10:43 -07:00
vlan_core.c net: gro: skb_gro_header helper function 2022-08-25 10:33:21 +02:00
vlan_dev.c vlan: fix a potential uninit-value in vlan_dev_hard_start_xmit() 2023-05-17 12:55:39 +01:00
vlan_gvrp.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
vlan_mvrp.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
vlan_netlink.c vlan: fix memory leak in vlan_newlink() 2022-07-09 12:26:59 +01:00
vlan.c net: add netif_inherit_tso_max() 2022-05-06 12:07:56 +01:00
vlan.h vlan: introduce vlan_dev_free_egress_priority 2022-02-09 13:33:39 +00:00
vlanproc.c vlan: use correct format characters 2022-03-17 16:34:49 -07:00
vlanproc.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00