mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-10-30 16:07:39 +00:00
No description
de3510e52b
Memory backed or zoned null block devices may generate actual request timeout errors due to the submission path being blocked on memory allocation or zone locking. Unlike fake timeouts or injected timeouts, the request submission path will call blk_mq_complete_request() or blk_mq_end_request() for these real timeout errors, causing a double completion and use after free situation as the block layer timeout handler executes blk_mq_rq_timed_out() and __blk_mq_free_request() in blk_mq_check_expired(). This problem often triggers a NULL pointer dereference such as: BUG: kernel NULL pointer dereference, address: 0000000000000050 RIP: 0010:blk_mq_sched_mark_restart_hctx+0x5/0x20 ... Call Trace: dd_finish_request+0x56/0x80 blk_mq_free_request+0x37/0x130 null_handle_cmd+0xbf/0x250 [null_blk] ? null_queue_rq+0x67/0xd0 [null_blk] blk_mq_dispatch_rq_list+0x122/0x850 __blk_mq_do_dispatch_sched+0xbb/0x2c0 __blk_mq_sched_dispatch_requests+0x13d/0x190 blk_mq_sched_dispatch_requests+0x30/0x60 __blk_mq_run_hw_queue+0x49/0x90 process_one_work+0x26c/0x580 worker_thread+0x55/0x3c0 ? process_one_work+0x580/0x580 kthread+0x134/0x150 ? kthread_create_worker_on_cpu+0x70/0x70 ret_from_fork+0x1f/0x30 This problem very often triggers when running the full btrfs xfstests on a memory-backed zoned null block device in a VM with limited amount of memory. Avoid this by executing blk_mq_complete_request() in null_timeout_rq() only for commands that are marked for a fake timeout completion using the fake_timeout boolean in struct null_cmd. For timeout errors injected through debugfs, the timeout handler will execute blk_mq_complete_request()i as before. This is safe as the submission path does not execute complete requests in this case. In null_timeout_rq(), also make sure to set the command error field to BLK_STS_TIMEOUT and to propagate this error through to the request completion. Reported-by: Johannes Thumshirn <Johannes.Thumshirn@wdc.com> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com> Tested-by: Johannes Thumshirn <Johannes.Thumshirn@wdc.com> Reviewed-by: Johannes Thumshirn <Johannes.Thumshirn@wdc.com> Link: https://lore.kernel.org/r/20210331225244.126426-1-damien.lemoal@wdc.com Signed-off-by: Jens Axboe <axboe@kernel.dk> |
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| 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.
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.