| From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2021-47637: ubifs: Fix deadlock in concurrent rename whiteout and inode writeback |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| ubifs: Fix deadlock in concurrent rename whiteout and inode writeback |
| |
| Following hung tasks: |
| [ 77.028764] task:kworker/u8:4 state:D stack: 0 pid: 132 |
| [ 77.028820] Call Trace: |
| [ 77.029027] schedule+0x8c/0x1b0 |
| [ 77.029067] mutex_lock+0x50/0x60 |
| [ 77.029074] ubifs_write_inode+0x68/0x1f0 [ubifs] |
| [ 77.029117] __writeback_single_inode+0x43c/0x570 |
| [ 77.029128] writeback_sb_inodes+0x259/0x740 |
| [ 77.029148] wb_writeback+0x107/0x4d0 |
| [ 77.029163] wb_workfn+0x162/0x7b0 |
| |
| [ 92.390442] task:aa state:D stack: 0 pid: 1506 |
| [ 92.390448] Call Trace: |
| [ 92.390458] schedule+0x8c/0x1b0 |
| [ 92.390461] wb_wait_for_completion+0x82/0xd0 |
| [ 92.390469] __writeback_inodes_sb_nr+0xb2/0x110 |
| [ 92.390472] writeback_inodes_sb_nr+0x14/0x20 |
| [ 92.390476] ubifs_budget_space+0x705/0xdd0 [ubifs] |
| [ 92.390503] do_rename.cold+0x7f/0x187 [ubifs] |
| [ 92.390549] ubifs_rename+0x8b/0x180 [ubifs] |
| [ 92.390571] vfs_rename+0xdb2/0x1170 |
| [ 92.390580] do_renameat2+0x554/0x770 |
| |
| , are caused by concurrent rename whiteout and inode writeback processes: |
| rename_whiteout(Thread 1) wb_workfn(Thread2) |
| ubifs_rename |
| do_rename |
| lock_4_inodes (Hold ui_mutex) |
| ubifs_budget_space |
| make_free_space |
| shrink_liability |
| __writeback_inodes_sb_nr |
| bdi_split_work_to_wbs (Queue new wb work) |
| wb_do_writeback(wb work) |
| __writeback_single_inode |
| ubifs_write_inode |
| LOCK(ui_mutex) |
| ↑ |
| wb_wait_for_completion (Wait wb work) <-- deadlock! |
| |
| Reproducer (Detail program in [Link]): |
| 1. SYS_renameat2("/mp/dir/file", "/mp/dir/whiteout", RENAME_WHITEOUT) |
| 2. Consume out of space before kernel(mdelay) doing budget for whiteout |
| |
| Fix it by doing whiteout space budget before locking ubifs inodes. |
| BTW, it also fixes wrong goto tag 'out_release' in whiteout budget |
| error handling path(It should at least recover dir i_size and unlock |
| 4 ubifs inodes). |
| |
| The Linux kernel CVE team has assigned CVE-2021-47637 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 4.9 with commit 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798 and fixed in 4.19.238 with commit 9dddc8211430fb851ddf0b168e3a00c6f66cc185 |
| Issue introduced in 4.9 with commit 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798 and fixed in 5.4.189 with commit 37bdf1ad592555ecda1d55b89f6e393e4c0589d1 |
| Issue introduced in 4.9 with commit 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798 and fixed in 5.10.110 with commit 83e42a78428fc354f5e2049935b84c8d8d29b787 |
| Issue introduced in 4.9 with commit 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798 and fixed in 5.15.33 with commit c58af8564a7b08757173009030b74baf4b2b762b |
| Issue introduced in 4.9 with commit 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798 and fixed in 5.16.19 with commit 70e9090acc32348cedc5def0cd6d5c126efc97b9 |
| Issue introduced in 4.9 with commit 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798 and fixed in 5.17.2 with commit 8b278c8dcfb565cb65eceb62a38cbf7a7c326db5 |
| Issue introduced in 4.9 with commit 9e0a1fff8db56eaaebb74b4a3ef65f86811c4798 and fixed in 5.18 with commit afd427048047e8efdedab30e8888044e2be5aa9c |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2021-47637 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| fs/ubifs/dir.c |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/9dddc8211430fb851ddf0b168e3a00c6f66cc185 |
| https://git.kernel.org/stable/c/37bdf1ad592555ecda1d55b89f6e393e4c0589d1 |
| https://git.kernel.org/stable/c/83e42a78428fc354f5e2049935b84c8d8d29b787 |
| https://git.kernel.org/stable/c/c58af8564a7b08757173009030b74baf4b2b762b |
| https://git.kernel.org/stable/c/70e9090acc32348cedc5def0cd6d5c126efc97b9 |
| https://git.kernel.org/stable/c/8b278c8dcfb565cb65eceb62a38cbf7a7c326db5 |
| https://git.kernel.org/stable/c/afd427048047e8efdedab30e8888044e2be5aa9c |
