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

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syzbot

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Sep 15, 2020, 6:13:23 AM9/15/20
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Hello,

syzbot found the following issue on:

HEAD commit: a87f9628 Linux 4.19.145
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=15e2ee53900000
kernel config: https://syzkaller.appspot.com/x/.config?x=6c1d3a90df2d2f09
dashboard link: https://syzkaller.appspot.com/bug?extid=70b24c3816befdfd7785
compiler: gcc (GCC) 10.1.0-syz 20200507

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+70b24c...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-out-of-bounds in tcp_orphan_retries net/ipv4/tcp_timer.c:139 [inline]
BUG: KASAN: slab-out-of-bounds in tcp_probe_timer net/ipv4/tcp_timer.c:374 [inline]
BUG: KASAN: slab-out-of-bounds in tcp_write_timer_handler+0xa4b/0xa60 net/ipv4/tcp_timer.c:602
Read of size 4 at addr ffff8880a41d8828 by task swapper/1/0

CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.19.145-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1fc/0x2fe lib/dump_stack.c:118
print_address_description.cold+0x54/0x219 mm/kasan/report.c:256
kasan_report_error.cold+0x8a/0x1c7 mm/kasan/report.c:354
kasan_report mm/kasan/report.c:412 [inline]
__asan_report_load4_noabort+0x88/0x90 mm/kasan/report.c:432
tcp_orphan_retries net/ipv4/tcp_timer.c:139 [inline]
tcp_probe_timer net/ipv4/tcp_timer.c:374 [inline]
tcp_write_timer_handler+0xa4b/0xa60 net/ipv4/tcp_timer.c:602
tcp_write_timer+0x103/0x1b0 net/ipv4/tcp_timer.c:618
call_timer_fn+0x177/0x700 kernel/time/timer.c:1338
expire_timers+0x243/0x4e0 kernel/time/timer.c:1375
__run_timers kernel/time/timer.c:1703 [inline]
run_timer_softirq+0x21c/0x670 kernel/time/timer.c:1716
__do_softirq+0x26c/0x9a0 kernel/softirq.c:292
invoke_softirq kernel/softirq.c:372 [inline]
irq_exit+0x215/0x260 kernel/softirq.c:412
exiting_irq arch/x86/include/asm/apic.h:544 [inline]
smp_apic_timer_interrupt+0x136/0x550 arch/x86/kernel/apic/apic.c:1094
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:894
</IRQ>
RIP: 0010:native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:61
Code: 48 89 df e8 44 1c 61 fa e9 2e ff ff ff 48 89 df e8 37 1c 61 fa eb 82 90 90 90 90 90 e9 07 00 00 00 0f 00 2d 24 2b 49 00 fb f4 <c3> 90 e9 07 00 00 00 0f 00 2d 14 2b 49 00 f4 c3 90 90 41 56 41 55
RSP: 0018:ffff8880a9f4fd58 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
RAX: 1ffffffff11a4b6c RBX: dffffc0000000000 RCX: 0000000000000000
RDX: dffffc0000000000 RSI: 0000000000000001 RDI: ffff8880a9f3cc44
RBP: 0000000000000001 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff88d25b50
R13: 1ffff110153e9fb5 R14: 0000000000000000 R15: 0000000000000000
arch_safe_halt arch/x86/include/asm/paravirt.h:94 [inline]
default_idle+0x49/0x310 arch/x86/kernel/process.c:557
cpuidle_idle_call kernel/sched/idle.c:153 [inline]
do_idle+0x2ec/0x4b0 kernel/sched/idle.c:263
cpu_startup_entry+0xc5/0xe0 kernel/sched/idle.c:369
start_secondary+0x41f/0x580 arch/x86/kernel/smpboot.c:271
secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

Allocated by task 3696:
kmem_cache_alloc+0x122/0x370 mm/slab.c:3559
getname_flags+0xce/0x590 fs/namei.c:140
do_sys_open+0x26c/0x520 fs/open.c:1079
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 3696:
__cache_free mm/slab.c:3503 [inline]
kmem_cache_free+0x7f/0x260 mm/slab.c:3765
putname+0xe1/0x120 fs/namei.c:261
do_sys_open+0x2ba/0x520 fs/open.c:1094
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8880a41d8900
which belongs to the cache names_cache of size 4096
The buggy address is located 216 bytes to the left of
4096-byte region [ffff8880a41d8900, ffff8880a41d9900)
The buggy address belongs to the page:
page:ffffea0002907600 count:1 mapcount:0 mapping:ffff8880aa00ab40 index:0x0 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffffea000245a608 ffffea0002907688 ffff8880aa00ab40
raw: 0000000000000000 ffff8880a41d8900 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880a41d8700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880a41d8780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880a41d8800: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
^
ffff8880a41d8880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880a41d8900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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syzbot

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Jan 13, 2021, 5:13:20 AM1/13/21
to syzkaller...@googlegroups.com
Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.
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