# CVE-2024-46687: btrfs: fix a use-after-free when hitting errors inside btrfs_submit_chunk()

> A use-after-free vulnerability in the Linux kernel's btrfs filesystem allows attackers to cause a denial of service or potentially execute code.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 13 Sep 2024
- **Updated:** 5 Aug 2026
- **Also known as:** AZL-49291, BELL-CVE-2024-46687, DEBIAN-CVE-2024-46687, GHSA-grj2-x9v7-7qqx, UBUNTU-CVE-2024-46687

## What is CVE-2024-46687?

CVE-2024-46687 is a high-severity use after free vulnerability in Linux kernel, published on 13 Sep 2024. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

btrfs: fix a use-after-free when hitting errors inside btrfs_submit_chunk()

[BUG]
There is an internal report that KASAN is reporting use-after-free, with
the following backtrace:

  BUG: KASAN: slab-use-after-free in btrfs_check_read_bio+0xa68/0xb70 [btrfs]
  Read of size 4 at addr ffff8881117cec28 by task kworker/u16:2/45
  CPU: 1 UID: 0 PID: 45 Comm: kworker/u16:2 Not tainted 6.11.0-rc2-next-20240805-default+ #76
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-3-gd478f380-rebuilt.opensuse.org 04/01/2014
  Workqueue: btrfs-endio btrfs_end_bio_work [btrfs]
  Call Trace:
   dump_stack_lvl+0x61/0x80
   print_address_description.constprop.0+0x5e/0x2f0
   print_report+0x118/0x216
   kasan_report+0x11d/0x1f0
   btrfs_check_read_bio+0xa68/0xb70 [btrfs]
   process_one_work+0xce0/0x12a0
   worker_thread+0x717/0x1250
   kthread+0x2e3/0x3c0
   ret_from_fork+0x2d/0x70
   ret_from_fork_asm+0x11/0x20

  Allocated by task 20917:
   kasan_save_stack+0x37/0x60
   kasan_save_track+0x10/0x30
   __kasan_slab_alloc+0x7d/0x80
   kmem_cache_alloc_noprof+0x16e/0x3e0
   mempool_alloc_noprof+0x12e/0x310
   bio_alloc_bioset+0x3f0/0x7a0
   btrfs_bio_alloc+0x2e/0x50 [btrfs]
   submit_extent_page+0x4d1/0xdb0 [btrfs]
   btrfs_do_readpage+0x8b4/0x12a0 [btrfs]
   btrfs_readahead+0x29a/0x430 [btrfs]
   read_pages+0x1a7/0xc60
   page_cache_ra_unbounded+0x2ad/0x560
   filemap_get_pages+0x629/0xa20
   filemap_read+0x335/0xbf0
   vfs_read+0x790/0xcb0
   ksys_read+0xfd/0x1d0
   do_syscall_64+0x6d/0x140
   entry_SYSCALL_64_after_hwframe+0x4b/0x53

  Freed by task 20917:
   kasan_save_stack+0x37/0x60
   kasan_save_track+0x10/0x30
   kasan_save_free_info+0x37/0x50
   __kasan_slab_free+0x4b/0x60
   kmem_cache_free+0x214/0x5d0
   bio_free+0xed/0x180
   end_bbio_data_read+0x1cc/0x580 [btrfs]
   btrfs_submit_chunk+0x98d/0x1880 [btrfs]
   btrfs_submit_bio+0x33/0x70 [btrfs]
   submit_one_bio+0xd4/0x130 [btrfs]
   submit_extent_page+0x3ea/0xdb0 [btrfs]
   btrfs_do_readpage+0x8b4/0x12a0 [btrfs]
   btrfs_readahead+0x29a/0x430 [btrfs]
   read_pages+0x1a7/0xc60
   page_cache_ra_unbounded+0x2ad/0x560
   filemap_get_pages+0x629/0xa20
   filemap_read+0x335/0xbf0
   vfs_read+0x790/0xcb0
   ksys_read+0xfd/0x1d0
   do_syscall_64+0x6d/0x140
   entry_SYSCALL_64_after_hwframe+0x4b/0x53

[CAUSE]
Although I cannot reproduce the error, the report itself is good enough
to pin down the cause.

The call trace is the regular endio workqueue context, but the
free-by-task trace is showing that during btrfs_submit_chunk() we
already hit a critical error, and is calling btrfs_bio_end_io() to error
out.  And the original endio function called bio_put() to free the whole
bio.

This means a double freeing thus causing use-after-free, e.g.:

1. Enter btrfs_submit_bio() with a read bio
   The read bio length is 128K, crossing two 64K stripes.

2. The first run of btrfs_submit_chunk()

2.1 Call btrfs_map_block(), which returns 64K
2.2 Call btrfs_split_bio()
    Now there are two bios, one referring to the first 64K, the other
    referring to the second 64K.
2.3 The first half is submitted.

3. The second run of btrfs_submit_chunk()

3.1 Call btrfs_map_block(), which by somehow failed
    Now we call btrfs_bio_end_io() to handle the error

3.2 btrfs_bio_end_io() calls the original endio function
    Which is end_bbio_data_read(), and it calls bio_put() for the
    original bio.

    Now the original bio is freed.

4. The submitted first 64K bio finished
   Now we call into btrfs_check_read_bio() and tries to advance the bio
   iter.
   But since the original bio (thus its iter) is already freed, we
   trigger the above use-after free.

   And even if the memory is not poisoned/corrupted, we will later call
   the original endio function, causing a double freeing.

[FIX]
Instead of calling btrfs_bio_end_io(), call btrfs_orig_bbio_end_io(),
which has the extra check on split bios and do the pr
---truncated---

Weakness: CWE-416 (Use After Free), CWE-415 (Double Free)

## Which versions are affected by CVE-2024-46687?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-46687?

Apply the vendor's patch.

## Is CVE-2024-46687 being exploited?

There is no known exploitation of CVE-2024-46687 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-46687 and fix it if it is affected.

What it is: CVE-2024-46687 is a high-severity use after free vulnerability in Linux kernel, published on 13 Sep 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2024-46687 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2024-46687/ (Markdown: https://insights.sbomify.com/CVE-2024-46687/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-46687
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-46687
- OSV: https://osv.dev/vulnerability/CVE-2024-46687

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-46687/
Summaries are generated and may contain mistakes; the official description above is the record.