KASAN: use-after-free Read in rds_inc_put

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: dbc29aff Linux 4.19.74
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=116f78a1600000
kernel config: https://syzkaller.appspot.com/x/.config?x=c3b60234a72e3893
dashboard link: https://syzkaller.appspot.com/bug?extid=d286b07e2259eaea4282
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+d286b0...@syzkaller.appspotmail.com

netlink: 8 bytes leftover after parsing attributes in process
`syz-executor.1'.
==================================================================
BUG: KASAN: use-after-free in rds_inc_put+0x141/0x150 net/rds/recv.c:87
Read of size 8 at addr ffff88809a353ee8 by task syz-executor.0/7932

CPU: 1 PID: 7932 Comm: syz-executor.0 Not tainted 4.19.74 #0
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:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report mm/kasan/report.c:412 [inline]
kasan_report.cold+0x8c/0x2ba mm/kasan/report.c:396
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
rds_inc_put+0x141/0x150 net/rds/recv.c:87
rds_clear_recv_queue+0x157/0x380 net/rds/recv.c:761
rds_release+0x108/0x3c0 net/rds/af_rds.c:73
__sock_release+0xce/0x2a0 net/socket.c:579
sock_close+0x1b/0x30 net/socket.c:1140
__fput+0x2dd/0x8b0 fs/file_table.c:278
____fput+0x16/0x20 fs/file_table.c:309
task_work_run+0x145/0x1c0 kernel/task_work.c:113
exit_task_work include/linux/task_work.h:22 [inline]
do_exit+0x994/0x2fa0 kernel/exit.c:876
do_group_exit+0x135/0x370 kernel/exit.c:979
get_signal+0x3ec/0x1fc0 kernel/signal.c:2574
do_signal+0x95/0x1960 arch/x86/kernel/signal.c:821
exit_to_usermode_loop+0x244/0x2c0 arch/x86/entry/common.c:163
prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
syscall_return_slowpath arch/x86/entry/common.c:271 [inline]
do_syscall_64+0x53d/0x620 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459a09
Code: Bad RIP value.
RSP: 002b:00007f4e8f119cf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 000000000075bfd0 RCX: 0000000000459a09
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000075bfd0
RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000075bfd4
R13: 00007fff3265f91f R14: 00007f4e8f11a9c0 R15: 000000000075bfd4

The buggy address belongs to the page:
page:ffffea000268d4c0 count:0 mapcount:-128 mapping:0000000000000000
index:0x0
flags: 0x1fffc0000000000()
raw: 01fffc0000000000 ffffea0002448dc8 ffffea000254a808 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffff7f 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88809a353d80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88809a353e00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> ffff88809a353e80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff88809a353f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88809a353f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


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[syzbot]

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