KASAN: use-after-free Read in tasklet_action

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: c6db52a8 Linux 4.14.183
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=14cab6fe100000
kernel config: https://syzkaller.appspot.com/x/.config?x=98bbe4d18401ff4
dashboard link: https://syzkaller.appspot.com/bug?extid=6e383a6434b67479431f
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+6e383a...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in tasklet_action+0x29f/0x340 kernel/softirq.c:506
Read of size 8 at addr ffff88809f4ec9d0 by task syz-executor.4/14973

CPU: 1 PID: 14973 Comm: syz-executor.4 Not tainted 4.14.183-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+0x1b2/0x283 lib/dump_stack.c:58
print_address_description.cold+0x54/0x1dc mm/kasan/report.c:252
kasan_report_error mm/kasan/report.c:351 [inline]
kasan_report mm/kasan/report.c:409 [inline]
kasan_report.cold+0xa9/0x2b9 mm/kasan/report.c:393
tasklet_action+0x29f/0x340 kernel/softirq.c:506
__do_softirq+0x254/0x9bf kernel/softirq.c:288
do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1016
</IRQ>
do_softirq kernel/softirq.c:332 [inline]
do_softirq+0xdf/0x170 kernel/softirq.c:319
__local_bh_enable_ip+0x11d/0x160 kernel/softirq.c:185
sock_orphan include/net/sock.h:1712 [inline]
bcm_release+0x48b/0x5c0 net/can/bcm.c:1582
__sock_release+0xcd/0x2b0 net/socket.c:602
sock_close+0x15/0x20 net/socket.c:1139
__fput+0x25f/0x7a0 fs/file_table.c:210
task_work_run+0x113/0x190 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x1ad/0x200 arch/x86/entry/common.c:164
prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
do_syscall_64+0x4a3/0x640 arch/x86/entry/common.c:297
entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x416661
RSP: 002b:00007fff4a70bb60 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000004 RCX: 0000000000416661
RDX: 0000000000000001 RSI: 0000000000000080 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 00007fff4a70bc50 R11: 0000000000000293 R12: 00000000007915b0
R13: 000000000003e067 R14: ffffffffffffffff R15: 000000000078bf0c

Allocated by task 14976:
save_stack mm/kasan/kasan.c:447 [inline]
set_track mm/kasan/kasan.c:459 [inline]
kasan_kmalloc.part.0+0x4f/0xd0 mm/kasan/kasan.c:551
kmem_cache_alloc_trace+0x14d/0x3f0 mm/slab.c:3618
kmalloc include/linux/slab.h:488 [inline]
kzalloc include/linux/slab.h:661 [inline]
bcm_tx_setup net/can/bcm.c:952 [inline]
bcm_sendmsg+0x219c/0x3770 net/can/bcm.c:1388
sock_sendmsg_nosec net/socket.c:646 [inline]
sock_sendmsg+0xb5/0x100 net/socket.c:656
___sys_sendmsg+0x70a/0x840 net/socket.c:2062
__sys_sendmsg+0xa3/0x120 net/socket.c:2096
SYSC_sendmsg net/socket.c:2107 [inline]
SyS_sendmsg+0x27/0x40 net/socket.c:2103
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb

Freed by task 14973:
save_stack mm/kasan/kasan.c:447 [inline]
set_track mm/kasan/kasan.c:459 [inline]
kasan_slab_free+0xaf/0x190 mm/kasan/kasan.c:524
__cache_free mm/slab.c:3496 [inline]
kfree+0xcb/0x260 mm/slab.c:3815
bcm_release+0xff/0x5c0 net/can/bcm.c:1540
__sock_release+0xcd/0x2b0 net/socket.c:602
sock_close+0x15/0x20 net/socket.c:1139
__fput+0x25f/0x7a0 fs/file_table.c:210
task_work_run+0x113/0x190 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x1ad/0x200 arch/x86/entry/common.c:164
prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
do_syscall_64+0x4a3/0x640 arch/x86/entry/common.c:297
entry_SYSCALL_64_after_hwframe+0x46/0xbb

The buggy address belongs to the object at ffff88809f4ec900
which belongs to the cache kmalloc-1024 of size 1024
The buggy address is located 208 bytes inside of
1024-byte region [ffff88809f4ec900, ffff88809f4ecd00)
The buggy address belongs to the page:
page:ffffea00027d3b00 count:1 mapcount:0 mapping:ffff88809f4ec000 index:0xffff88809f4edb00 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffff88809f4ec000 ffff88809f4edb00 0000000100000001
raw: ffffea0002321120 ffffea00021167a0 ffff8880aa800ac0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88809f4ec880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88809f4ec900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88809f4ec980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88809f4eca00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88809f4eca80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This bug is generated by a bot. It may contain errors.
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[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit: c6db52a8 Linux 4.14.183
git tree: linux-4.14.y

console output: https://syzkaller.appspot.com/x/log.txt?x=142d4fd2100000

kernel config: https://syzkaller.appspot.com/x/.config?x=98bbe4d18401ff4
dashboard link: https://syzkaller.appspot.com/bug?extid=6e383a6434b67479431f
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=177e16fe100000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15e47e0e100000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+6e383a...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in tasklet_action+0x29f/0x340 kernel/softirq.c:506

Read of size 8 at addr ffff888091b5aa10 by task syz-executor859/7904

CPU: 1 PID: 7904 Comm: syz-executor859 Not tainted 4.14.183-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+0x1b2/0x283 lib/dump_stack.c:58
print_address_description.cold+0x54/0x1dc mm/kasan/report.c:252
kasan_report_error mm/kasan/report.c:351 [inline]
kasan_report mm/kasan/report.c:409 [inline]
kasan_report.cold+0xa9/0x2b9 mm/kasan/report.c:393
tasklet_action+0x29f/0x340 kernel/softirq.c:506
__do_softirq+0x254/0x9bf kernel/softirq.c:288
do_softirq_own_stack+0x2a/0x40 arch/x86/entry/entry_64.S:1016
</IRQ>
do_softirq kernel/softirq.c:332 [inline]
do_softirq+0xdf/0x170 kernel/softirq.c:319
__local_bh_enable_ip+0x11d/0x160 kernel/softirq.c:185
sock_orphan include/net/sock.h:1712 [inline]
bcm_release+0x48b/0x5c0 net/can/bcm.c:1582
__sock_release+0xcd/0x2b0 net/socket.c:602
sock_close+0x15/0x20 net/socket.c:1139
__fput+0x25f/0x7a0 fs/file_table.c:210
task_work_run+0x113/0x190 kernel/task_work.c:113

get_signal+0x1887/0x1c90 kernel/signal.c:2234
do_signal+0x7c/0x15d0 arch/x86/kernel/signal.c:814
exit_to_usermode_loop+0x160/0x200 arch/x86/entry/common.c:160

prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
do_syscall_64+0x4a3/0x640 arch/x86/entry/common.c:297
entry_SYSCALL_64_after_hwframe+0x46/0xbb

RIP: 0033:0x44a399
RSP: 002b:00007f19df5a8ce8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: 0000000000000080 RBX: 00000000006e0c28 RCX: 000000000044a399
RDX: 0000000000000000 RSI: 00000000200000c0 RDI: 0000000000000003
RBP: 00000000006e0c20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006e0c2c
R13: 00007ffe00f8f2cf R14: 00007f19df5a99c0 R15: 20c49ba5e353f7cf

Allocated by task 7904:

save_stack mm/kasan/kasan.c:447 [inline]
set_track mm/kasan/kasan.c:459 [inline]
kasan_kmalloc.part.0+0x4f/0xd0 mm/kasan/kasan.c:551
kmem_cache_alloc_trace+0x14d/0x3f0 mm/slab.c:3618
kmalloc include/linux/slab.h:488 [inline]
kzalloc include/linux/slab.h:661 [inline]
bcm_tx_setup net/can/bcm.c:952 [inline]
bcm_sendmsg+0x219c/0x3770 net/can/bcm.c:1388
sock_sendmsg_nosec net/socket.c:646 [inline]
sock_sendmsg+0xb5/0x100 net/socket.c:656
___sys_sendmsg+0x70a/0x840 net/socket.c:2062
__sys_sendmsg+0xa3/0x120 net/socket.c:2096
SYSC_sendmsg net/socket.c:2107 [inline]
SyS_sendmsg+0x27/0x40 net/socket.c:2103
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb

Freed by task 7904:

save_stack mm/kasan/kasan.c:447 [inline]
set_track mm/kasan/kasan.c:459 [inline]
kasan_slab_free+0xaf/0x190 mm/kasan/kasan.c:524
__cache_free mm/slab.c:3496 [inline]
kfree+0xcb/0x260 mm/slab.c:3815
bcm_release+0xff/0x5c0 net/can/bcm.c:1540
__sock_release+0xcd/0x2b0 net/socket.c:602
sock_close+0x15/0x20 net/socket.c:1139
__fput+0x25f/0x7a0 fs/file_table.c:210
task_work_run+0x113/0x190 kernel/task_work.c:113

get_signal+0x1887/0x1c90 kernel/signal.c:2234
do_signal+0x7c/0x15d0 arch/x86/kernel/signal.c:814
exit_to_usermode_loop+0x160/0x200 arch/x86/entry/common.c:160

prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
do_syscall_64+0x4a3/0x640 arch/x86/entry/common.c:297
entry_SYSCALL_64_after_hwframe+0x46/0xbb

The buggy address belongs to the object at ffff888091b5a940

which belongs to the cache kmalloc-1024 of size 1024
The buggy address is located 208 bytes inside of

1024-byte region [ffff888091b5a940, ffff888091b5ad40)

The buggy address belongs to the page:

page:ffffea000246d680 count:1 mapcount:0 mapping:ffff888091b5a040 index:0xffff888091b5bb40 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffff888091b5a040 ffff888091b5bb40 0000000100000001
raw: ffffea00024064a0 ffffea00027b5220 ffff8880aa800ac0 0000000000000000

page dumped because: kasan: bad access detected

Memory state around the buggy address:

ffff888091b5a900: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
ffff888091b5a980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888091b5aa00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888091b5aa80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888091b5ab00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================