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Commit6f8191fdf4("block: simplify disk shutdown") removed the call to blk_get_queue() during gendisk allocation but missed to remove the corresponding cleanup code blk_put_queue() for it. Thus, if the gendisk allocation fails, the request_queue refcount gets decremented and reaches 0, causing blk_mq_release() to be called with a hctx still alive. That triggers a WARNING report, as found by syzkaller: ------------[ cut here ]------------ WARNING: CPU: 0 PID: 23016 at block/blk-mq.c:3881 blk_mq_release+0xf8/0x3e0 block/blk-mq.c:3881 [...] stripped RIP: 0010:blk_mq_release+0xf8/0x3e0 block/blk-mq.c:3881 [...] stripped Call Trace: <TASK> blk_release_queue+0x153/0x270 block/blk-sysfs.c:780 kobject_cleanup lib/kobject.c:673 [inline] kobject_release lib/kobject.c:704 [inline] kref_put include/linux/kref.h:65 [inline] kobject_put+0x1c8/0x540 lib/kobject.c:721 __alloc_disk_node+0x4f7/0x610 block/genhd.c:1388 __blk_mq_alloc_disk+0x13b/0x1f0 block/blk-mq.c:3961 loop_add+0x3e2/0xaf0 drivers/block/loop.c:1978 loop_control_ioctl+0x133/0x620 drivers/block/loop.c:2150 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd [...] stripped Fixes:6f8191fdf4("block: simplify disk shutdown") Reported-by: syzbot+31c9594f6e43b9289b25@syzkaller.appspotmail.com Suggested-by: Hillf Danton <hdanton@sina.com> Signed-off-by: Rafael Mendonca <rafaelmendsr@gmail.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20220811232338.254673-1-rafaelmendsr@gmail.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
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.