CVE-2022-49850: In the Linux kernel, the following vulnerability has been resolved: nilfs2: fix deadlock in nilfs_count_free_blocks() A semaphore deadlock can occur if…

PriorityP420medium5.5CVSS 3.1

AVLACLPRLUINSUCNINAH

EPSS

0.16%

5.3th percentile

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

nilfs2: fix deadlock in nilfs_count_free_blocks()

A semaphore deadlock can occur if nilfs_get_block() detects metadata
corruption while locating data blocks and a superblock writeback occurs at
the same time:

task 1 task 2
------ ------
* A file operation *
nilfs_truncate()
nilfs_get_block()
down_read(rwsem A) mi_sem)
and then calls nilfs_bmap_lookup_contig(), but if it fails due to metadata
corruption, __nilfs_error() is called from nilfs_bmap_convert_error()
inside the lock section.

Since __nilfs_error() calls nilfs_set_error() unless the filesystem is
read-only and nilfs_set_error() attempts to writelock rwsem B (=
nilfs->ns_sem) to write back superblock exclusively, hierarchical lock
acquisition occurs in the order rwsem A -> rwsem B.

Now, if another task starts updating the superblock, it may writelock
rwsem B during the lock sequence above, and can deadlock trying to
readlock rwsem A in nilfs_count_free_blocks().

However, there is actually no need to take rwsem A in
nilfs_count_free_blocks() because it, within the lock section, only reads
a single integer data on a shared struct with
nilfs_sufile_get_ncleansegs(). This has been the case after commit
aa474a220180 ("nilfs2: add local variable to cache the number of clean
segments"), that is, even before this bug was introduced.

So, this resolves the deadlock problem by just not taking the semaphore in
nilfs_count_free_blocks().

Affected

22 ranges

Vendor	Product	Version range	Fixed in
debian	linux	< linux 6.0.10-1 (bookworm)	linux 6.0.10-1 (bookworm)
linux	linux	—	—
linux	linux	>= e828949e5b42bfd234ee537cdb7c5e3a577958a3 < 3c89ca6d3dfa6c09c515807a7a97a521f5d5147e	3c89ca6d3dfa6c09c515807a7a97a521f5d5147e
linux	linux	>= e828949e5b42bfd234ee537cdb7c5e3a577958a3 < 8b4506cff6630bb474bb46a2a75c31e533a756ba	8b4506cff6630bb474bb46a2a75c31e533a756ba
linux	linux	>= e828949e5b42bfd234ee537cdb7c5e3a577958a3 < f0cc93080d4c09510b74ecba87fd778cca390bb1	f0cc93080d4c09510b74ecba87fd778cca390bb1
linux	linux	>= e828949e5b42bfd234ee537cdb7c5e3a577958a3 < 36ff974b0310771417c0be64b64aa221bd70d63d	36ff974b0310771417c0be64b64aa221bd70d63d
linux	linux	>= e828949e5b42bfd234ee537cdb7c5e3a577958a3 < 1d4ff73062096c21b47954d2996b4df259777bda	1d4ff73062096c21b47954d2996b4df259777bda
linux	linux	>= e828949e5b42bfd234ee537cdb7c5e3a577958a3 < abc082aac0d9b6b926038fc3adb7008306581be2	abc082aac0d9b6b926038fc3adb7008306581be2
linux	linux	>= e828949e5b42bfd234ee537cdb7c5e3a577958a3 < cb029b54953420f7a2d65100f1c5107f14411bdc	cb029b54953420f7a2d65100f1c5107f14411bdc
linux	linux	>= e828949e5b42bfd234ee537cdb7c5e3a577958a3 < 8ac932a4921a96ca52f61935dbba64ea87bbd5dc	8ac932a4921a96ca52f61935dbba64ea87bbd5dc
linux	linux_kernel	—	—
linux	linux_kernel	>= 0 < 5.10.158-1	5.10.158-1
linux	linux_kernel	>= 0 < 6.0.10-1	6.0.10-1
linux	linux_kernel	>= 0 < 6.0.10-1	6.0.10-1
linux	linux_kernel	>= 0 < 6.0.10-1	6.0.10-1
linux	linux_kernel	>= 2.6.38 < 4.9.334	4.9.334
linux	linux_kernel	>= 4.10 < 4.14.300	4.14.300
linux	linux_kernel	>= 4.15 < 4.19.267	4.19.267
linux	linux_kernel	>= 4.20 < 5.4.225	5.4.225
linux	linux_kernel	>= 5.11 < 5.15.79	5.15.79
linux	linux_kernel	>= 5.16 < 6.0.9	6.0.9
linux	linux_kernel	>= 5.5 < 5.10.155	5.10.155

CVSS provenance

nvdv3.15.5MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

osv5.5MEDIUM

vendor_debian5.5MEDIUM

vendor_redhat5.5MEDIUM

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