Description

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

btrfs: fix error propagation of split bios

The purpose of btrfs_bbio_propagate_error() shall be propagating an error
of split bio to its original btrfs_bio, and tell the error to the upper
layer. However, it's not working well on some cases.

* Case 1. Immediate (or quick) end_bio with an error

When btrfs sends btrfs_bio to mirrored devices, btrfs calls
btrfs_bio_end_io() when all the mirroring bios are completed. If that
btrfs_bio was split, it is from btrfs_clone_bioset and its end_io function
is btrfs_orig_write_end_io. For this case, btrfs_bbio_propagate_error()
accesses the orig_bbio's bio context to increase the error count.

That works well in most cases. However, if the end_io is called enough
fast, orig_bbio's (remaining part after split) bio context may not be
properly set at that time. Since the bio context is set when the orig_bbio
(the last btrfs_bio) is sent to devices, that might be too late for earlier
split btrfs_bio's completion. That will result in NULL pointer
dereference.

That bug is easily reproducible by running btrfs/146 on zoned devices [1]
and it shows the following trace.

[1] You need raid-stripe-tree feature as it create "-d raid0 -m raid1" FS.

BUG: kernel NULL pointer dereference, address: 0000000000000020
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: Oops: 0000 [#1] PREEMPT SMP PTI
CPU: 1 UID: 0 PID: ...

Classification

CVE ID: CVE-2024-50225

CVSS Base Severity: MEDIUM

CVSS Base Score: 5.5

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

Affected Products

Vendor: Linux

Product: Linux

Exploit Prediction Scoring System (EPSS)

EPSS Score: 0.03% (probability of being exploited)

EPSS Percentile: 5.58% (scored less or equal to compared to others)

EPSS Date: 2025-06-02 (when was this score calculated)

References

https://nvd.nist.gov/vuln/detail/CVE-2024-50225
https://git.kernel.org/stable/c/22833d89b780ba0f9f66e19c477e7decf638edce
https://git.kernel.org/stable/c/d48e1dea3931de64c26717adc2b89743c7ab6594

Timeline