CVE-2024-47680 Information

Description

In the Linux kernel the following vulnerability has been resolved:

f2fs: check discard support for conventional zones

As the helper function f2fs_bdev_support_discard() shows f2fs checks if the target block devices support discard by calling bdev_max_discard_sectors() and bdev_is_zoned(). This check works well for most cases but it does not work for conventional zones on zoned block devices. F2fs assumes that zoned block devices support discard and calls __submit_discard_cmd(). When __submit_discard_cmd() is called for sequential write required zones it works fine since __submit_discard_cmd() issues zone reset commands instead of discard commands. However when __submit_discard_cmd() is called for conventional zones __blkdev_issue_discard() is called even when the devices do not support discard.

The inappropriate __blkdev_issue_discard() call was not a problem before the commit 30f1e7241422 (lock: move discard checks into the ioctl handler) because __blkdev_issue_discard() checked if the target devices support discard or not. If not it returned EOPNOTSUPP. After the commit __blkdev_issue_discard() no longer checks it. It always returns zero and sets NULL to the given bio pointer. This NULL pointer triggers f2fs_bug_on() in __submit_discard_cmd(). The BUG is recreated with the commands below at the umount step where /dev/nullb0 is a zoned null_blk with 5GB total size 128MB zone size and 10 conventional zones.

$ mkfs.f2fs -f -m /dev/nullb0 $ mount /dev/nullb0 /mnt $ for ((i=0;i<5;i++)); do dd if=/dev/zero of=/mnt/test bs=65536 count=1600 conv=fsync; done $ umount /mnt

To fix the BUG avoid the inappropriate __blkdev_issue_discard() call. When discard is requested for conventional zones check if the device supports discard or not. If not return EOPNOTSUPP.

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Reference

https://git.kernel.org/stable/c/7bd7ce68ddad5a28565e42ef21cacaff113773a9 https://git.kernel.org/stable/c/d2352b57897f6a3349666fc318dcbec99092c6a5 https://git.kernel.org/stable/c/43aec4d01bd2ce961817a777b3846f8318f398e4

Attack Complexity

LOW

Privileges Required

LOW

User Interaction Required

LOW

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

NONE

Availability Impact

NONE

Base Score

HIGH

Base Severity

5.5