4.7

CVE-2021-47599

btrfs: use latest_dev in btrfs_show_devname

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.
Daten sind bereitgestellt durch National Vulnerability Database (NVD)
Linux ≫ Linux Kernel Version < 5.15.11
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Zu dieser CVE wurde keine Warnung gefunden.
EPSS Metriken
Typ Quelle Score Percentile
EPSS FIRST.org 0.15% 0.043
CVSS Metriken
Quelle Base Score Exploit Score Impact Score Vector String
nvd@nist.gov 4.7 1 3.6
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

https://git.kernel.org/stable/c/6605fd2f394bba0a0059df2b6cfc87b0b6d393a2
Patch
https://git.kernel.org/stable/c/e342c2558016ead462f376b6c6c2ac5efc17f3b1
Patch