This bug is a in the Linux kernel, specifically in the filesystem / io_uring / audit areas.
** Package changed: ubuntu => linux (Ubuntu) -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/2043841 Title: kernel BUG: io_uring openat triggers audit reference count underflow Status in linux-azure-6.2 package in Ubuntu: New Bug description: I first encountered a bug in 6.2.0-1012-azure #12~22.04.1-Ubuntu that occurs during io_uring openat audit processing. I have a kernel patch that was accepted into the upstream kernel as well as the v6.6, v6.5.9, and v6.1.60 releases. The bug was first introduced in the upstream v5.16 kernel. I do not see the change yet in: * The Ubuntu-azure-6.2-6.2.0-1017.17_22.04.1 tag in the jammy kernel repository. * The Ubuntu-azure-6.5.0-1009.9 tag in the mantic kernel repository. Can this upstream commit be cherry picked? The upstream commit is: 03adc61edad49e1bbecfb53f7ea5d78f398fe368 The upstream patch thread is: https://lore.kernel.org/audit/20231012215518.ga4...@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net/T/#u The maintainer pull request thread is: https://lore.kernel.org/lkml/20231019-kampfsport- metapher-e5211d7be247@brauner The pre-patch discussion thread is: https://lore.kernel.org/io- uring/mw2pr2101mb1033fff044a258f84aeaa584f1...@mw2pr2101mb1033.namprd21.prod.outlook.com/T/#u The commit log message is: commit 03adc61edad49e1bbecfb53f7ea5d78f398fe368 Author: Dan Clash <dacl...@linux.microsoft.com> Date: Thu Oct 12 14:55:18 2023 -0700 audit,io_uring: io_uring openat triggers audit reference count underflow An io_uring openat operation can update an audit reference count from multiple threads resulting in the call trace below. A call to io_uring_submit() with a single openat op with a flag of IOSQE_ASYNC results in the following reference count updates. These first part of the system call performs two increments that do not race. do_syscall_64() __do_sys_io_uring_enter() io_submit_sqes() io_openat_prep() __io_openat_prep() getname() getname_flags() /* update 1 (increment) */ __audit_getname() /* update 2 (increment) */ The openat op is queued to an io_uring worker thread which starts the opportunity for a race. The system call exit performs one decrement. do_syscall_64() syscall_exit_to_user_mode() syscall_exit_to_user_mode_prepare() __audit_syscall_exit() audit_reset_context() putname() /* update 3 (decrement) */ The io_uring worker thread performs one increment and two decrements. These updates can race with the system call decrement. io_wqe_worker() io_worker_handle_work() io_wq_submit_work() io_issue_sqe() io_openat() io_openat2() do_filp_open() path_openat() __audit_inode() /* update 4 (increment) */ putname() /* update 5 (decrement) */ __audit_uring_exit() audit_reset_context() putname() /* update 6 (decrement) */ The fix is to change the refcnt member of struct audit_names from int to atomic_t. kernel BUG at fs/namei.c:262! Call Trace: ... ? putname+0x68/0x70 audit_reset_context.part.0.constprop.0+0xe1/0x300 __audit_uring_exit+0xda/0x1c0 io_issue_sqe+0x1f3/0x450 ? lock_timer_base+0x3b/0xd0 io_wq_submit_work+0x8d/0x2b0 ? __try_to_del_timer_sync+0x67/0xa0 io_worker_handle_work+0x17c/0x2b0 io_wqe_worker+0x10a/0x350 Cc: sta...@vger.kernel.org Link: https://lore.kernel.org/lkml/mw2pr2101mb1033fff044a258f84aeaa584f1...@mw2pr2101mb1033.namprd21.prod.outlook.com/ Fixes: 5bd2182d58e9 ("audit,io_uring,io-wq: add some basic audit support to io_uring") Signed-off-by: Dan Clash <dacl...@linux.microsoft.com> Link: https://lore.kernel.org/r/20231012215518.ga4...@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net Reviewed-by: Jens Axboe <ax...@kernel.dk> Signed-off-by: Christian Brauner <brau...@kernel.org> To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux-azure-6.2/+bug/2043841/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
