Executive Summary



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Informations
Name CVE-2022-49834 First vendor Publication 2025-05-01
Vendor Cve Last vendor Modification 2025-05-01

Security-Database Scoring CVSS v3

Cvss vector : N/A
Overall CVSS Score NA
Base Score NA Environmental Score NA
impact SubScore NA Temporal Score NA
Exploitabality Sub Score NA
 
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Security-Database Scoring CVSS v2

Cvss vector :
Cvss Base Score N/A Attack Range N/A
Cvss Impact Score N/A Attack Complexity N/A
Cvss Expoit Score N/A Authentication N/A
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Detail

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

nilfs2: fix use-after-free bug of ns_writer on remount

If a nilfs2 filesystem is downgraded to read-only due to metadata corruption on disk and is remounted read/write, or if emergency read-only remount is performed, detaching a log writer and synchronizing the filesystem can be done at the same time.

In these cases, use-after-free of the log writer (hereinafter nilfs->ns_writer) can happen as shown in the scenario below:

Task1 Task2
-------------------------------- ------------------------------
nilfs_construct_segment
nilfs_segctor_sync
init_wait
init_waitqueue_entry
add_wait_queue
schedule
nilfs_remount (R/W remount case)
nilfs_attach_log_writer
nilfs_detach_log_writer
nilfs_segctor_destroy
kfree
finish_wait
_raw_spin_lock_irqsave
__raw_spin_lock_irqsave
do_raw_spin_lock
debug_spin_lock_before <-- use-after-free

While Task1 is sleeping, nilfs->ns_writer is freed by Task2. After Task1 waked up, Task1 accesses nilfs->ns_writer which is already freed. This scenario diagram is based on the Shigeru Yoshida's post [1].

This patch fixes the issue by not detaching nilfs->ns_writer on remount so that this UAF race doesn't happen. Along with this change, this patch also inserts a few necessary read-only checks with superblock instance where only the ns_writer pointer was used to check if the filesystem is read-only.

Original Source

Url : http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-49834

Sources (Detail)

https://git.kernel.org/stable/c/39a3ed68270b079c6b874d4e4727a512b9b4882c
https://git.kernel.org/stable/c/4feedde5486c07ea79787839153a71ca71329c7d
https://git.kernel.org/stable/c/8cccf05fe857a18ee26e20d11a8455a73ffd4efd
https://git.kernel.org/stable/c/9b162e81045266a2d5b44df9dffdf05c54de9cca
https://git.kernel.org/stable/c/afbd1188382a75f6cfe22c0b68533f7f9664f182
https://git.kernel.org/stable/c/b152300d5a1ba4258dacf9916bff20e6a8c7603b
https://git.kernel.org/stable/c/b2fbf10040216ef5ee270773755fc2f5da65b749
https://git.kernel.org/stable/c/b4736ab5542112fe0a40f140a0a0b072954f34da
Source Url

Alert History

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0
Date Informations
2025-05-27 02:12:02
  • First insertion