| 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-2021-47599: btrfs: use latest_dev in btrfs_show_devname |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| btrfs: use latest_dev in btrfs_show_devname |
| |
| The test case btrfs/238 reports the warning below: |
| |
| WARNING: CPU: 3 PID: 481 at fs/btrfs/super.c:2509 btrfs_show_devname+0x104/0x1e8 [btrfs] |
| CPU: 2 PID: 1 Comm: systemd Tainted: G W O 5.14.0-rc1-custom #72 |
| Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015 |
| Call trace: |
| btrfs_show_devname+0x108/0x1b4 [btrfs] |
| show_mountinfo+0x234/0x2c4 |
| m_show+0x28/0x34 |
| seq_read_iter+0x12c/0x3c4 |
| vfs_read+0x29c/0x2c8 |
| ksys_read+0x80/0xec |
| __arm64_sys_read+0x28/0x34 |
| invoke_syscall+0x50/0xf8 |
| do_el0_svc+0x88/0x138 |
| el0_svc+0x2c/0x8c |
| el0t_64_sync_handler+0x84/0xe4 |
| el0t_64_sync+0x198/0x19c |
| |
| Reason: |
| While btrfs_prepare_sprout() moves the fs_devices::devices into |
| fs_devices::seed_list, the btrfs_show_devname() searches for the devices |
| and found none, leading to the warning as in above. |
| |
| Fix: |
| latest_dev is updated according to the changes to the device list. |
| That means we could use the latest_dev->name to show the device name in |
| /proc/self/mounts, the pointer will be always valid as it's assigned |
| before the device is deleted from the list in remove or replace. |
| The RCU protection is sufficient as the device structure is freed after |
| synchronization. |
| |
| The Linux kernel CVE team has assigned CVE-2021-47599 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Fixed in 5.15.11 with commit e342c2558016ead462f376b6c6c2ac5efc17f3b1 |
| Fixed in 5.16 with commit 6605fd2f394bba0a0059df2b6cfc87b0b6d393a2 |
| |
| 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-2021-47599 |
| 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/btrfs/super.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/e342c2558016ead462f376b6c6c2ac5efc17f3b1 |
| https://git.kernel.org/stable/c/6605fd2f394bba0a0059df2b6cfc87b0b6d393a2 |
