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There is a problem if we are going to unmap a rbd device and the
watch_dwork is going to queue delayed work for watch:
unmap Thread watch Thread timer
do_rbd_remove
cancel_tasks_sync(rbd_dev)
queue_delayed_work for watch
destroy_workqueue(rbd_dev->task_wq)
drain_workqueue(wq)
destroy other resources in wq
call_timer_fn
__queue_work()
Then the delayed work escape the cancel_tasks_sync() and
destroy_workqueue() and we will get an user-after-free call trace:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
PGD 0 P4D 0
Oops: 0000 [#1] SMP PTI
Modules linked in:
CPU: 7 PID: 0 Comm: swapper/7 Tainted: G OE 4.17.0-rc6+ #13
Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
RIP: 0010:__queue_work+0x6a/0x3b0
RSP: 0018:ffff9427df1c3e90 EFLAGS: 00010086
RAX: ffff9427deca8400 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff9427deca8400 RSI: ffff9427df1c3e50 RDI: 0000000000000000
RBP: ffff942783e39e00 R08: ffff9427deca8400 R09: ffff9427df1c3f00
R10: 0000000000000004 R11: 0000000000000005 R12: ffff9427cfb85970
R13: 0000000000002000 R14: 000000000001eca0 R15: 0000000000000007
FS: 0000000000000000(0000) GS:ffff9427df1c0000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 00000004c900a005 CR4: 00000000000206e0
Call Trace:
<IRQ>
? __queue_work+0x3b0/0x3b0
call_timer_fn+0x2d/0x130
run_timer_softirq+0x16e/0x430
? tick_sched_timer+0x37/0x70
__do_softirq+0xd2/0x280
irq_exit+0xd5/0xe0
smp_apic_timer_interrupt+0x6c/0x130
apic_timer_interrupt+0xf/0x20
[ Move rbd_dev->watch_dwork cancellation so that rbd_reregister_watch()
either bails out early because the watch is UNREGISTERED at that point
or just gets cancelled. ]
Cc: stable@vger.kernel.org
Fixes:
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|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.