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

Hello,

syzbot found the following issue on:

HEAD commit: 29c52025 Linux 4.14.221
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=10d5357f500000
kernel config: https://syzkaller.appspot.com/x/.config?x=83f668f81cfc5600
dashboard link: https://syzkaller.appspot.com/bug?extid=5d9c74c22a58196140a8

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: [email protected]

audit: type=1804 audit(1614046099.943:396): pid=30514 uid=0 auid=4294967295 ses=4294967295 op="invalid_pcr" cause="open_writers" comm="syz-executor.5" name="/root/syzkaller-testdir719148418/syzkaller.DYs7wp/1119/file0/bus" dev="loop5" ino=67 res=1
FAT-fs (loop5): Invalid FSINFO signature: 0x00000000, 0x00000000 (sector = 1)
==================================================================
BUG: KASAN: slab-out-of-bounds in tcp_retransmit_timer+0x245f/0x28c0 net/ipv4/tcp_timer.c:471
Read of size 8 at addr ffff8880a03c8378 by task swapper/1/0

CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.14.221-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:17 [inline]
dump_stack+0x1b2/0x281 lib/dump_stack.c:58
print_address_description.cold+0x54/0x1d3 mm/kasan/report.c:252
kasan_report_error.cold+0x8a/0x191 mm/kasan/report.c:351
kasan_report mm/kasan/report.c:409 [inline]
__asan_report_load8_noabort+0x68/0x70 mm/kasan/report.c:430
tcp_retransmit_timer+0x245f/0x28c0 net/ipv4/tcp_timer.c:471
tcp_write_timer_handler+0x434/0x780 net/ipv4/tcp_timer.c:583
tcp_write_timer+0xc8/0x160 net/ipv4/tcp_timer.c:601
call_timer_fn+0x14a/0x650 kernel/time/timer.c:1280
expire_timers+0x232/0x4d0 kernel/time/timer.c:1319
__run_timers kernel/time/timer.c:1637 [inline]
run_timer_softirq+0x1d5/0x5a0 kernel/time/timer.c:1650
__do_softirq+0x24d/0x9ff kernel/softirq.c:288
invoke_softirq kernel/softirq.c:368 [inline]
irq_exit+0x193/0x240 kernel/softirq.c:409
exiting_irq arch/x86/include/asm/apic.h:638 [inline]
smp_apic_timer_interrupt+0x141/0x5e0 arch/x86/kernel/apic/apic.c:1106
apic_timer_interrupt+0x93/0xa0 arch/x86/entry/entry_64.S:793
</IRQ>
RIP: 0010:native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:61
RSP: 0018:ffff8880b5477e68 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff10
RAX: 1ffffffff11e1254 RBX: dffffc0000000000 RCX: 0000000000000000
RDX: dffffc0000000000 RSI: 0000000000000001 RDI: ffff8880b5468bc4
RBP: ffffffff88f09290 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffed1016a8d068
R13: ffff8880b5468340 R14: 0000000000000000 R15: 0000000000000000
arch_safe_halt arch/x86/include/asm/paravirt.h:94 [inline]
default_idle+0x47/0x370 arch/x86/kernel/process.c:558
cpuidle_idle_call kernel/sched/idle.c:156 [inline]
do_idle+0x250/0x3c0 kernel/sched/idle.c:246
cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:351
start_secondary+0x4db/0x670 arch/x86/kernel/smpboot.c:272
secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:240

Allocated by task 4629:
save_stack mm/kasan/kasan.c:447 [inline]
set_track mm/kasan/kasan.c:459 [inline]
kasan_kmalloc+0xeb/0x160 mm/kasan/kasan.c:551
kmem_cache_alloc+0x124/0x3c0 mm/slab.c:3552
getname_flags+0xc8/0x550 fs/namei.c:138
user_path_at_empty+0x2a/0x50 fs/namei.c:2631
user_path_at include/linux/namei.h:57 [inline]
vfs_statx+0xd1/0x180 fs/stat.c:185
vfs_lstat include/linux/fs.h:3070 [inline]
SYSC_newlstat fs/stat.c:350 [inline]
SyS_newlstat+0x83/0xe0 fs/stat.c:344
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb

Freed by task 4629:
save_stack mm/kasan/kasan.c:447 [inline]
set_track mm/kasan/kasan.c:459 [inline]
kasan_slab_free+0xc3/0x1a0 mm/kasan/kasan.c:524
__cache_free mm/slab.c:3496 [inline]
kmem_cache_free+0x7c/0x2b0 mm/slab.c:3758
putname+0xcd/0x110 fs/namei.c:259
filename_lookup+0x37b/0x510 fs/namei.c:2386
user_path_at include/linux/namei.h:57 [inline]
vfs_statx+0xd1/0x180 fs/stat.c:185
vfs_lstat include/linux/fs.h:3070 [inline]
SYSC_newlstat fs/stat.c:350 [inline]
SyS_newlstat+0x83/0xe0 fs/stat.c:344
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb

The buggy address belongs to the object at ffff8880a03c86c0
which belongs to the cache names_cache of size 4096
The buggy address is located 840 bytes to the left of
4096-byte region [ffff8880a03c86c0, ffff8880a03c96c0)
The buggy address belongs to the page:
page:ffffea000280f200 count:1 mapcount:0 mapping:ffff8880a03c86c0 index:0x0 compound_mapcount: 0
flags: 0xfff00000008100(slab|head)
raw: 00fff00000008100 ffff8880a03c86c0 0000000000000000 0000000100000001
raw: ffffea0002593fa0 ffffea000280f2a0 ffff88823f8bb200 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880a03c8200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880a03c8280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880a03c8300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
^
ffff8880a03c8380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880a03c8400: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at [email protected].

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

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