KASAN: slab-out-of-bounds Read in skb_gso_transport_seglen

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: d71f695c Linux 4.14.179
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=114b5b70100000
kernel config: https://syzkaller.appspot.com/x/.config?x=580f01c69a690433
dashboard link: https://syzkaller.appspot.com/bug?extid=e0b5cfed4ac23a208501
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+e0b5cf...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-out-of-bounds in __tcp_hdrlen include/linux/tcp.h:35 [inline]
BUG: KASAN: slab-out-of-bounds in tcp_hdrlen include/linux/tcp.h:40 [inline]
BUG: KASAN: slab-out-of-bounds in skb_gso_transport_seglen+0x2df/0x300 net/core/skbuff.c:4944
Read of size 2 at addr ffff888066eb8a8c by task syz-executor.5/29803

CPU: 1 PID: 29803 Comm: syz-executor.5 Not tainted 4.14.179-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x13e/0x194 lib/dump_stack.c:58
print_address_description.cold+0x7c/0x1e2 mm/kasan/report.c:252
kasan_report_error mm/kasan/report.c:351 [inline]
kasan_report mm/kasan/report.c:409 [inline]
kasan_report.cold+0xa9/0x2ae mm/kasan/report.c:393
__tcp_hdrlen include/linux/tcp.h:35 [inline]
tcp_hdrlen include/linux/tcp.h:40 [inline]
skb_gso_transport_seglen+0x2df/0x300 net/core/skbuff.c:4944
skb_gso_mac_seglen include/linux/skbuff.h:4124 [inline]
tbf_enqueue+0x248/0x930 net/sched/sch_tbf.c:191
__dev_xmit_skb net/core/dev.c:3229 [inline]
__dev_queue_xmit+0x12dc/0x25c0 net/core/dev.c:3493
packet_snd net/packet/af_packet.c:3012 [inline]
packet_sendmsg+0x1bf7/0x54b0 net/packet/af_packet.c:3037
sock_sendmsg_nosec net/socket.c:646 [inline]
sock_sendmsg+0xc5/0x100 net/socket.c:656
SYSC_sendto+0x1c4/0x2b0 net/socket.c:1763
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45c829
RSP: 002b:00007f8044138c78 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 0000000000500fa0 RCX: 000000000045c829
RDX: 0000000000004e60 RSI: 0000000020000180 RDI: 0000000000000003
RBP: 000000000078bf00 R08: 0000000000000000 R09: fffffffffffffe5d
R10: 0000000000000810 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000a0f R14: 00000000004ccc62 R15: 00007f80441396d4

Allocated by task 29803:
save_stack+0x32/0xa0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_kmalloc mm/kasan/kasan.c:551 [inline]
kasan_kmalloc+0xbf/0xe0 mm/kasan/kasan.c:529
__do_kmalloc_node mm/slab.c:3682 [inline]
__kmalloc_node_track_caller+0x4c/0x70 mm/slab.c:3696
__kmalloc_reserve.isra.0+0x35/0xd0 net/core/skbuff.c:137
__alloc_skb+0xca/0x4c0 net/core/skbuff.c:205
alloc_skb include/linux/skbuff.h:980 [inline]
alloc_skb_with_frags+0x85/0x4f0 net/core/skbuff.c:5228
sock_alloc_send_pskb+0x586/0x6d0 net/core/sock.c:2081
packet_alloc_skb net/packet/af_packet.c:2862 [inline]
packet_snd net/packet/af_packet.c:2957 [inline]
packet_sendmsg+0x1529/0x54b0 net/packet/af_packet.c:3037
sock_sendmsg_nosec net/socket.c:646 [inline]
sock_sendmsg+0xc5/0x100 net/socket.c:656
SYSC_sendto+0x1c4/0x2b0 net/socket.c:1763
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 1:
save_stack+0x32/0xa0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_slab_free+0x75/0xc0 mm/kasan/kasan.c:524
__cache_free mm/slab.c:3496 [inline]
kfree+0xcb/0x260 mm/slab.c:3815
kernfs_fop_release+0x10d/0x180 fs/kernfs/file.c:783
__fput+0x25f/0x790 fs/file_table.c:210
task_work_run+0x113/0x190 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x1d6/0x220 arch/x86/entry/common.c:164
prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
do_syscall_64+0x4a3/0x640 arch/x86/entry/common.c:297
entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff888066eb8840
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 76 bytes to the right of
512-byte region [ffff888066eb8840, ffff888066eb8a40)
The buggy address belongs to the page:
page:ffffea00019bae00 count:1 mapcount:0 mapping:ffff888066eb80c0 index:0xffff888066eb8d40
flags: 0xfffe0000000100(slab)
raw: 00fffe0000000100 ffff888066eb80c0 ffff888066eb8d40 0000000100000003
raw: ffffea00021da660 ffffea0001690160 ffff88812fe54940 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff888066eb8980: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888066eb8a00: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
>ffff888066eb8a80: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
^
ffff888066eb8b00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888066eb8b80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.