---
id: CVE-2024-56565
title: 'f2fs: fix to drop all discards after creating snapshot on lvm device'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  f2fs: fix to drop all discards after creating snapshot on lvm device

  Piergiorgio reported a bug in bugzilla as below:

  ------------[ cut here ]------------
  WARNING: CP…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 35ec7d5748849762008e8ae9f8ad2766229d5794 <
    0f3b00763dae90e94eed94a39d32d252d8750e9d
  - >-
    Linux >= 35ec7d5748849762008e8ae9f8ad2766229d5794 <
    ed24ab98242f8d22b66fbe0452c97751b5ea4e22
  - >-
    Linux >= 35ec7d5748849762008e8ae9f8ad2766229d5794 <
    15136c3861a3341db261ebdbb6ae4ae1765635e2
  - >-
    Linux >= 35ec7d5748849762008e8ae9f8ad2766229d5794 <
    bc8aeb04fd80cb8cfae3058445c84410fd0beb5e
  - Linux 4.19
published: '2024-12-27'
updated: '2026-10-30'
sourceUpdated: '2026-10-30T12:20:18.174Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2024-56565'
references:
  - url: 'https://git.kernel.org/stable/c/0f3b00763dae90e94eed94a39d32d252d8750e9d'
  - url: 'https://git.kernel.org/stable/c/ed24ab98242f8d22b66fbe0452c97751b5ea4e22'
  - url: 'https://git.kernel.org/stable/c/15136c3861a3341db261ebdbb6ae4ae1765635e2'
  - url: 'https://git.kernel.org/stable/c/bc8aeb04fd80cb8cfae3058445c84410fd0beb5e'
tags:
  - cve.org
epss: 0.0022
epssPercentile: 0.12576
ingestedAt: '2026-11-03T14:47:02.525Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

f2fs: fix to drop all discards after creating snapshot on lvm device

Piergiorgio reported a bug in bugzilla as below:

------------[ cut here ]------------
WARNING: CPU: 2 PID: 969 at fs/f2fs/segment.c:1330
RIP: 0010:__submit_discard_cmd+0x27d/0x400 [f2fs]
Call Trace:
 __issue_discard_cmd+0x1ca/0x350 [f2fs]
 issue_discard_thread+0x191/0x480 [f2fs]
 kthread+0xcf/0x100
 ret_from_fork+0x31/0x50
 ret_from_fork_asm+0x1a/0x30

w/ below testcase, it can reproduce this bug quickly:
- pvcreate /dev/vdb
- vgcreate myvg1 /dev/vdb
- lvcreate -L 1024m -n mylv1 myvg1
- mount /dev/myvg1/mylv1 /mnt/f2fs
- dd if=/dev/zero of=/mnt/f2fs/file bs=1M count=20
- sync
- rm /mnt/f2fs/file
- sync
- lvcreate -L 1024m -s -n mylv1-snapshot /dev/myvg1/mylv1
- umount /mnt/f2fs

The root cause is: it will update discard_max_bytes of mounted lvm
device to zero after creating snapshot on this lvm device, then,
__submit_discard_cmd() will pass parameter @nr_sects w/ zero value
to __blkdev_issue_discard(), it returns a NULL bio pointer, result
in panic.

This patch changes as below for fixing:
1. Let's drop all remained discards in f2fs_unfreeze() if snapshot
of lvm device is created.
2. Checking discard_max_bytes before submitting discard during
__submit_discard_cmd().

## Affected

- `Linux >= 35ec7d5748849762008e8ae9f8ad2766229d5794 < 0f3b00763dae90e94eed94a39d32d252d8750e9d`
- `Linux >= 35ec7d5748849762008e8ae9f8ad2766229d5794 < ed24ab98242f8d22b66fbe0452c97751b5ea4e22`
- `Linux >= 35ec7d5748849762008e8ae9f8ad2766229d5794 < 15136c3861a3341db261ebdbb6ae4ae1765635e2`
- `Linux >= 35ec7d5748849762008e8ae9f8ad2766229d5794 < bc8aeb04fd80cb8cfae3058445c84410fd0beb5e`
- `Linux 4.19`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.