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SubjectRe: KASAN: use-after-free Write in skb_release_data (2)
From
syzbot has found a reproducer for the following crash on:

HEAD commit: 68cc2999 Merge branch 'devlink-small-spring-cleanup'
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13737c07200000
kernel config: https://syzkaller.appspot.com/x/.config?x=9ab5bbbbf283c99a
dashboard link: https://syzkaller.appspot.com/bug?extid=580be3953ed99133804f
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=123a3d3b200000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11d34f93200000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+580be3953ed99133804f@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in atomic_sub_return
include/asm-generic/atomic-instrumented.h:159 [inline]
BUG: KASAN: use-after-free in skb_release_data+0x11d/0x7a0
net/core/skbuff.c:566
Write of size 4 at addr ffff88808dee74e0 by task syz-executor887/7877

CPU: 0 PID: 7877 Comm: syz-executor887 Not tainted 5.0.0+ #108
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x172/0x1f0 lib/dump_stack.c:113
print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187
kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
check_memory_region_inline mm/kasan/generic.c:185 [inline]
check_memory_region+0x123/0x190 mm/kasan/generic.c:191
kasan_check_write+0x14/0x20 mm/kasan/common.c:108
atomic_sub_return include/asm-generic/atomic-instrumented.h:159 [inline]
skb_release_data+0x11d/0x7a0 net/core/skbuff.c:566
skb_release_all+0x4d/0x60 net/core/skbuff.c:631
__kfree_skb net/core/skbuff.c:645 [inline]
kfree_skb net/core/skbuff.c:663 [inline]
kfree_skb+0xe8/0x390 net/core/skbuff.c:657
skb_queue_purge+0x19/0x40 net/core/skbuff.c:2906
packet_release+0x8eb/0xbf0 net/packet/af_packet.c:3026
__sock_release+0xd3/0x2b0 net/socket.c:599
sock_close+0x1b/0x30 net/socket.c:1247
__fput+0x2e5/0x8d0 fs/file_table.c:278
____fput+0x16/0x20 fs/file_table.c:309
task_work_run+0x14a/0x1c0 kernel/task_work.c:113
exit_task_work include/linux/task_work.h:22 [inline]
do_exit+0x90a/0x2fa0 kernel/exit.c:876
do_group_exit+0x135/0x370 kernel/exit.c:980
get_signal+0x399/0x1d50 kernel/signal.c:2575
do_signal+0x87/0x1940 arch/x86/kernel/signal.c:816
exit_to_usermode_loop+0x244/0x2c0 arch/x86/entry/common.c:162
prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
do_syscall_64+0x52d/0x610 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4474d9
Code: 7a 6c 69 62 77 00 73 74 72 65 61 6d 2e 63 00 6f 70 65 6e 20 65 72 72
6f 72 20 25 64 2c 20 66 69 6c 65 20 27 25 73 27 3a 20 25 <73> 0a 00 66 69
6c 65 20 25 64 20 69 73 20 61 20 74 74 79 2d 74 79
RSP: 002b:00007f7ce163fdb8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00000000006ddc38 RCX: 00000000004474d9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00000000006ddc38
RBP: 00000000006ddc30 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006ddc3c
R13: 00007ffe04f36bbf R14: 00007f7ce16409c0 R15: 000000000000002d

Allocated by task 7876:
save_stack+0x45/0xd0 mm/kasan/common.c:75
set_track mm/kasan/common.c:87 [inline]
__kasan_kmalloc mm/kasan/common.c:497 [inline]
__kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:470
kasan_kmalloc+0x9/0x10 mm/kasan/common.c:511
__do_kmalloc_node mm/slab.c:3686 [inline]
__kmalloc_node_track_caller+0x4e/0x70 mm/slab.c:3700
__kmalloc_reserve.isra.0+0x40/0xf0 net/core/skbuff.c:140
__alloc_skb+0x10b/0x5e0 net/core/skbuff.c:208
alloc_skb_fclone include/linux/skbuff.h:1107 [inline]
sk_stream_alloc_skb+0x113/0xd10 net/ipv4/tcp.c:889
tcp_connect+0xfd8/0x4280 net/ipv4/tcp_output.c:3521
tcp_v4_connect+0x1514/0x1c40 net/ipv4/tcp_ipv4.c:315
__inet_stream_connect+0x83f/0xea0 net/ipv4/af_inet.c:659
tcp_sendmsg_fastopen net/ipv4/tcp.c:1158 [inline]
tcp_sendmsg_locked+0x2314/0x34d0 net/ipv4/tcp.c:1200
tcp_sendmsg+0x30/0x50 net/ipv4/tcp.c:1434
inet_sendmsg+0x147/0x5e0 net/ipv4/af_inet.c:802
sock_sendmsg_nosec net/socket.c:651 [inline]
sock_sendmsg+0xdd/0x130 net/socket.c:661
__sys_sendto+0x262/0x380 net/socket.c:1932
__do_sys_sendto net/socket.c:1944 [inline]
__se_sys_sendto net/socket.c:1940 [inline]
__x64_sys_sendto+0xe1/0x1a0 net/socket.c:1940
do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 7877:
save_stack+0x45/0xd0 mm/kasan/common.c:75
set_track mm/kasan/common.c:87 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/common.c:459
kasan_slab_free+0xe/0x10 mm/kasan/common.c:467
__cache_free mm/slab.c:3498 [inline]
kfree+0xcf/0x230 mm/slab.c:3821
skb_free_head+0x93/0xb0 net/core/skbuff.c:557
skb_release_data+0x576/0x7a0 net/core/skbuff.c:577
skb_release_all+0x4d/0x60 net/core/skbuff.c:631
__kfree_skb net/core/skbuff.c:645 [inline]
kfree_skb net/core/skbuff.c:663 [inline]
kfree_skb+0xe8/0x390 net/core/skbuff.c:657
skb_queue_purge+0x19/0x40 net/core/skbuff.c:2906
packet_release+0x8eb/0xbf0 net/packet/af_packet.c:3026
__sock_release+0xd3/0x2b0 net/socket.c:599
sock_close+0x1b/0x30 net/socket.c:1247
__fput+0x2e5/0x8d0 fs/file_table.c:278
____fput+0x16/0x20 fs/file_table.c:309
task_work_run+0x14a/0x1c0 kernel/task_work.c:113
exit_task_work include/linux/task_work.h:22 [inline]
do_exit+0x90a/0x2fa0 kernel/exit.c:876
do_group_exit+0x135/0x370 kernel/exit.c:980
get_signal+0x399/0x1d50 kernel/signal.c:2575
do_signal+0x87/0x1940 arch/x86/kernel/signal.c:816
exit_to_usermode_loop+0x244/0x2c0 arch/x86/entry/common.c:162
prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
do_syscall_64+0x52d/0x610 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff88808dee7200
which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 736 bytes inside of
1024-byte region [ffff88808dee7200, ffff88808dee7600)
The buggy address belongs to the page:
page:ffffea000237b980 count:1 mapcount:0 mapping:ffff88812c3f0ac0 index:0x0
compound_mapcount: 0
flags: 0x1fffc0000010200(slab|head)
raw: 01fffc0000010200 ffffea000224ba08 ffffea0002a63288 ffff88812c3f0ac0
raw: 0000000000000000 ffff88808dee6000 0000000100000007 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88808dee7380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88808dee7400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff88808dee7480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88808dee7500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88808dee7580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

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