d7e10d4769
Abaci Robot reported following panic: BUG: kernel NULL pointer dereference, address: 0000000000000000 PGD 800000010ef3f067 P4D 800000010ef3f067 PUD 10d9df067 PMD 0 Oops: 0002 [#1] SMP PTI CPU: 0 PID: 1869 Comm: io_wqe_worker-0 Not tainted 5.11.0-rc3+ #1 Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011 RIP: 0010:put_files_struct+0x1b/0x120 Code: 24 18 c7 00 f4 ff ff ff e9 4d fd ff ff 66 90 0f 1f 44 00 00 41 57 41 56 49 89 fe 41 55 41 54 55 53 48 83 ec 08 e8 b5 6b db ff 41 ff 0e 74 13 48 83 c4 08 5b 5d 41 5c 41 5d 41 5e 41 5f e9 9c RSP: 0000:ffffc90002147d48 EFLAGS: 00010293 RAX: 0000000000000000 RBX: ffff88810d9a5300 RCX: 0000000000000000 RDX: ffff88810d87c280 RSI: ffffffff8144ba6b RDI: 0000000000000000 RBP: 0000000000000080 R08: 0000000000000001 R09: ffffffff81431500 R10: ffff8881001be000 R11: 0000000000000000 R12: ffff88810ac2f800 R13: ffff88810af38a00 R14: 0000000000000000 R15: ffff8881057130c0 FS: 0000000000000000(0000) GS:ffff88813bc00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 000000010dbaa002 CR4: 00000000003706f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __io_clean_op+0x10c/0x2a0 io_dismantle_req+0x3c7/0x600 __io_free_req+0x34/0x280 io_put_req+0x63/0xb0 io_worker_handle_work+0x60e/0x830 ? io_wqe_worker+0x135/0x520 io_wqe_worker+0x158/0x520 ? __kthread_parkme+0x96/0xc0 ? io_worker_handle_work+0x830/0x830 kthread+0x134/0x180 ? kthread_create_worker_on_cpu+0x90/0x90 ret_from_fork+0x1f/0x30 Modules linked in: CR2: 0000000000000000 ---[ end trace c358ca86af95b1e7 ]--- I guess case below can trigger above panic: there're two threads which operates different io_uring ctxs and share same sqthread identity, and later one thread exits, io_uring_cancel_task_requests() will clear task->io_uring->identity->files to be NULL in sqpoll mode, then another ctx that uses same identity will panic. Indeed we don't need to clear task->io_uring->identity->files here, io_grab_identity() should handle identity->files changes well, if task->io_uring->identity->files is not equal to current->files, io_cow_identity() should handle this changes well. Cc: stable@vger.kernel.org # 5.5+ Reported-by: Abaci Robot <abaci@linux.alibaba.com> Signed-off-by: Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com> Reviewed-by: Pavel Begunkov <asml.silence@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.