KASAN: use-after-free Read in cma_cancel_listens

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 3b7c59a1 Merge tag 'pinctrl-v5.4-2' of git://git.kernel.or..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12b639ff600000
kernel config: https://syzkaller.appspot.com/x/.config?x=6c03e4d33fa96d51
dashboard link: https://syzkaller.appspot.com/bug?extid=57a3b121df74c4eccbc7
compiler: clang version 9.0.0 (/home/glider/llvm/clang
80fee25776c2fb61e74c1ecb1a523375c2500b69)

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+57a3b1...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in __list_del_entry_valid+0x9c/0x100
lib/list_debug.c:54
Read of size 8 at addr ffff888097eda1e8 by task syz-executor.2/15086

CPU: 1 PID: 15086 Comm: syz-executor.2 Not tainted 5.4.0-rc4+ #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+0x1d8/0x2f8 lib/dump_stack.c:113
print_address_description+0x75/0x5c0 mm/kasan/report.c:374
__kasan_report+0x14b/0x1c0 mm/kasan/report.c:506
kasan_report+0x26/0x50 mm/kasan/common.c:634
__asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
__list_del_entry_valid+0x9c/0x100 lib/list_debug.c:54
__list_del_entry include/linux/list.h:131 [inline]
list_del include/linux/list.h:139 [inline]
cma_cancel_listens+0x40/0x390 drivers/infiniband/core/cma.c:1750
cma_cancel_operation drivers/infiniband/core/cma.c:1778 [inline]
rdma_destroy_id+0x44f/0x1080 drivers/infiniband/core/cma.c:1842
ucma_close+0x1eb/0x2c0 drivers/infiniband/core/ucma.c:1762
__fput+0x2e4/0x740 fs/file_table.c:280
____fput+0x15/0x20 fs/file_table.c:313
task_work_run+0x17e/0x1b0 kernel/task_work.c:113
exit_task_work include/linux/task_work.h:22 [inline]
do_exit+0x5e8/0x2190 kernel/exit.c:817
do_group_exit+0x15c/0x2b0 kernel/exit.c:921
get_signal+0x4ac/0x1d60 kernel/signal.c:2734
do_signal+0x37/0x640 arch/x86/kernel/signal.c:815
exit_to_usermode_loop arch/x86/entry/common.c:159 [inline]
prepare_exit_to_usermode+0x303/0x580 arch/x86/entry/common.c:194
syscall_return_slowpath+0x113/0x4a0 arch/x86/entry/common.c:274
do_syscall_64+0x11f/0x1c0 arch/x86/entry/common.c:300
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459ef9
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7
48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
ff 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007faedb0c5cf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 000000000075bf28 RCX: 0000000000459ef9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000075bf28
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000075bf2c
R13: 00007ffe74d4703f R14: 00007faedb0c69c0 R15: 000000000075bf2c

Allocated by task 15089:
save_stack mm/kasan/common.c:69 [inline]
set_track mm/kasan/common.c:77 [inline]
__kasan_kmalloc+0x11c/0x1b0 mm/kasan/common.c:510
kasan_kmalloc+0x9/0x10 mm/kasan/common.c:524
kmem_cache_alloc_trace+0x221/0x2f0 mm/slab.c:3550
kmalloc include/linux/slab.h:556 [inline]
kzalloc include/linux/slab.h:690 [inline]
__rdma_create_id+0x66/0x480 drivers/infiniband/core/cma.c:882
ucma_create_id+0x250/0x540 drivers/infiniband/core/ucma.c:501
ucma_write+0x2da/0x360 drivers/infiniband/core/ucma.c:1684
__vfs_write+0xb8/0x740 fs/read_write.c:494
vfs_write+0x275/0x590 fs/read_write.c:558
ksys_write+0x117/0x220 fs/read_write.c:611
__do_sys_write fs/read_write.c:623 [inline]
__se_sys_write fs/read_write.c:620 [inline]
__x64_sys_write+0x7b/0x90 fs/read_write.c:620
do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 15272:
save_stack mm/kasan/common.c:69 [inline]
set_track mm/kasan/common.c:77 [inline]
kasan_set_free_info mm/kasan/common.c:332 [inline]
__kasan_slab_free+0x12a/0x1e0 mm/kasan/common.c:471
kasan_slab_free+0xe/0x10 mm/kasan/common.c:480
__cache_free mm/slab.c:3425 [inline]
kfree+0x115/0x200 mm/slab.c:3756
rdma_destroy_id+0xea2/0x1080 drivers/infiniband/core/cma.c:1877
ucma_close+0x1eb/0x2c0 drivers/infiniband/core/ucma.c:1762
__fput+0x2e4/0x740 fs/file_table.c:280
____fput+0x15/0x20 fs/file_table.c:313
task_work_run+0x17e/0x1b0 kernel/task_work.c:113
get_signal+0x1ca8/0x1d60 kernel/signal.c:2528
do_signal+0x37/0x640 arch/x86/kernel/signal.c:815
exit_to_usermode_loop arch/x86/entry/common.c:159 [inline]
prepare_exit_to_usermode+0x303/0x580 arch/x86/entry/common.c:194
syscall_return_slowpath+0x113/0x4a0 arch/x86/entry/common.c:274
do_syscall_64+0x11f/0x1c0 arch/x86/entry/common.c:300
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff888097eda000
which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 488 bytes inside of
2048-byte region [ffff888097eda000, ffff888097eda800)
The buggy address belongs to the page:
page:ffffea00025fb680 refcount:1 mapcount:0 mapping:ffff8880aa400e00
index:0x0
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea0002982a08 ffffea0002561a48 ffff8880aa400e00
raw: 0000000000000000 ffff888097eda000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff888097eda080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888097eda100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff888097eda180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888097eda200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888097eda280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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[Hillf Danton]

On Wed, 23 Oct 2019 22:41:06 -0700

Detect and avoid repeated cancelation.

--- a/drivers/infiniband/core/cma.c
+++ b/drivers/infiniband/core/cma.c
@@ -1747,7 +1747,9 @@ static void cma_cancel_listens(struct rd
* additional listen requests.
*/
mutex_lock(&lock);
- list_del(&id_priv->list);
+ if (list_empty(&id_priv->list))
+ goto unlock;
+ list_del_init(&id_priv->list);

while (!list_empty(&id_priv->listen_list)) {
dev_id_priv = list_entry(id_priv->listen_list.next,
@@ -1760,6 +1762,7 @@ static void cma_cancel_listens(struct rd
rdma_destroy_id(&dev_id_priv->id);
mutex_lock(&lock);
}
+unlock:
mutex_unlock(&lock);
}

[Jason Gunthorpe]

On Thu, Oct 24, 2019 at 07:57:00PM +0800, Hillf Danton wrote:
> Detect and avoid repeated cancelation.
>

> +++ b/drivers/infiniband/core/cma.c
> @@ -1747,7 +1747,9 @@ static void cma_cancel_listens(struct rd
> * additional listen requests.
> */
> mutex_lock(&lock);
> - list_del(&id_priv->list);
> + if (list_empty(&id_priv->list))
> + goto unlock;
> + list_del_init(&id_priv->list);
>
> while (!list_empty(&id_priv->listen_list)) {
> dev_id_priv = list_entry(id_priv->listen_list.next,
> @@ -1760,6 +1762,7 @@ static void cma_cancel_listens(struct rd
> rdma_destroy_id(&dev_id_priv->id);
> mutex_lock(&lock);
> }
> +unlock:
> mutex_unlock(&lock);
> }

Hum, it seems like a harmless change, but the real issue here is that
cma_cancel_listens() was called twice at all.

It seems pretty clear that the intent was it would be called on the
state, and the state is transitioned away before it is called. Ie see
how cma_cancel_operation() works with the 'state' argument.

So the only way to trigger this is to race two state transitions,
which means this is the usual syzkaller bug, the 'cma_exch'
synchronization scheme is just totally broken.

Jason

[syzbot]

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