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1133b93fc7
ublk_start_cancel() previously bailed out early when ublk_get_disk()
returned NULL, treating it as "our disk has been dead". That is correct
for the post-teardown case, but it also wrongly covers the pre-start
case: ublk_ctrl_start_dev() has not assigned ub->ub_disk yet, while
io_uring is already tearing down the daemon's uring_cmds via
ublk_uring_cmd_cancel_fn().
In that window, the cancel path skips ublk_set_canceling(), so
ubq->canceling stays false, even though ublk_cancel_cmd() goes on to
NULL out every io->cmd. ublk_ctrl_start_dev() then proceeds to set
ub->ub_disk, call add_disk(), and schedule partition_scan_work. When
ublk_partition_scan_work() runs bdev_disk_changed() and the resulting
read reaches ublk_queue_rq() -> ublk_queue_cmd(), the ubq->canceling
check passes and the code dereferences the NULL io->cmd:
BUG: kernel NULL pointer dereference, address: 0000000000000018
RIP: ublk_queue_cmd drivers/block/ublk_drv.c [inline]
RIP: ublk_queue_rq+0x73/0x100
Call Trace:
blk_mq_dispatch_rq_list+0x1c5/0xca0
...
bdev_disk_changed+0x3d4/0x5e0
ublk_partition_scan_work+0x89/0xe0
process_one_work+0x344/0x8a0
Fix it by always setting ub->canceling / ubq->canceling under
cancel_mutex. When the disk is allocated, keep the existing
quiesce/unquiesce dance so the flag is observed across the
ublk_queue_rq() barrier. When the disk is not yet allocated, there is
no request_queue and ublk_queue_rq() cannot be running concurrently, so
simply flipping the flag is sufficient: any subsequent I/O - including
the partition scan started by ublk_ctrl_start_dev() - will see
canceling set and be aborted via __ublk_queue_rq_common().
Fixes:
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| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .pylintrc | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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