Re: KASAN: slab-out-of-bounds Read in tls_push_record

[Dmitry Vyukov]

On Wed, Sep 26, 2018 at 9:49 AM syzbot
<syzbot+942a1909765f0413329b@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    739d0def85ca Merge branch 'hv_netvsc-Support-LRO-RSC-in-th..
> git tree:       net-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=13aa179e400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=e79b9299baeb2298
> dashboard link: https://syzkaller.appspot.com/bug?extid=942a1909765f0413329b
> compiler:       gcc (GCC) 8.0.1 20180413 (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+942a1909765f0413329b@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in sg_mark_end
> include/linux/scatterlist.h:195 [inline]
> BUG: KASAN: slab-out-of-bounds in tls_push_record+0x1243/0x1330
> net/tls/tls_sw.c:521
> Read of size 8 at addr ffff8801a4d235f8 by task syz-executor1/7668

This is probably:

#syz dup: KASAN: out-of-bounds Write in tls_push_record

> CPU: 1 PID: 7668 Comm: syz-executor1 Not tainted 4.19.0-rc4+ #228
> 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+0x1c4/0x2b4 lib/dump_stack.c:113
>   print_address_description.cold.8+0x9/0x1ff mm/kasan/report.c:256
>   kasan_report_error mm/kasan/report.c:354 [inline]
>   kasan_report.cold.9+0x242/0x309 mm/kasan/report.c:412
>   __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
>   sg_mark_end include/linux/scatterlist.h:195 [inline]
>   tls_push_record+0x1243/0x1330 net/tls/tls_sw.c:521
>   tls_sw_push_pending_record+0x22/0x30 net/tls/tls_sw.c:558
>   tls_handle_open_record net/tls/tls_main.c:155 [inline]
>   tls_sk_proto_close+0x439/0x750 net/tls/tls_main.c:272
>   inet_release+0x104/0x1f0 net/ipv4/af_inet.c:428
>   inet6_release+0x50/0x70 net/ipv6/af_inet6.c:458
>   __sock_release+0xd7/0x250 net/socket.c:579
>   sock_close+0x19/0x20 net/socket.c:1141
>   __fput+0x385/0xa30 fs/file_table.c:278
>   ____fput+0x15/0x20 fs/file_table.c:309
>   task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
>   tracehook_notify_resume include/linux/tracehook.h:193 [inline]
>   exit_to_usermode_loop+0x318/0x380 arch/x86/entry/common.c:166
>   prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
>   syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
>   do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x411151
> Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 34 19 00 00 c3 48
> 83 ec 08 e8 0a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48
> 89 c2 e8 53 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01
> RSP: 002b:00007fff8ba9e200 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
> RAX: 0000000000000000 RBX: 0000000000000005 RCX: 0000000000411151
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000001
> R10: 00007fff8ba9e130 R11: 0000000000000293 R12: 000000000000000f
> R13: 0000000000086e3d R14: 0000000000000412 R15: badc0ffeebadface
>
> Allocated by task 0:
> (stack is not available)
>
> Freed by task 0:
> (stack is not available)
>
> The buggy address belongs to the object at ffff8801a4d22d80
>   which belongs to the cache kmalloc-2048 of size 2048
> The buggy address is located 120 bytes to the right of
>   2048-byte region [ffff8801a4d22d80, ffff8801a4d23580)
> The buggy address belongs to the page:
> page:ffffea0006934880 count:1 mapcount:0 mapping:ffff8801da800c40 index:0x0
> compound_mapcount: 0
> flags: 0x2fffc0000008100(slab|head)
> raw: 02fffc0000008100 ffffea000717fd08 ffff8801da801948 ffff8801da800c40
> raw: 0000000000000000 ffff8801a4d22500 0000000100000003 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>   ffff8801a4d23480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>   ffff8801a4d23500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> > ffff8801a4d23580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>                                                                  ^
>   ffff8801a4d23600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>   ffff8801a4d23680: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ==================================================================
>
>
> ---
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>
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