Bugzilla – Bug 1226571
VUL-0: CVE-2021-47599: kernel: btrfs: use latest_dev in btrfs_show_devname
Last modified: 2024-06-21 21:01:11 UTC
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. References: http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2021-47599 https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2021/CVE-2021-47599.mbox https://git.kernel.org/stable/c/e342c2558016ead462f376b6c6c2ac5efc17f3b1 https://git.kernel.org/stable/c/6605fd2f394bba0a0059df2b6cfc87b0b6d393a2 https://www.cve.org/CVERecord?id=CVE-2021-47599
This is IMHO not a CVE material, a warning (with stack trace) printed under some conditions but otherwise nothing happens. That a warning is printed is AFAIK considedred a security thing because of panic-on-warn options that somebody might use. That's debatable but upstream stance is known. Nevertheless, it's a backport material.