Bug 2395222 (CVE-2023-53222)

Summary: CVE-2023-53222 kernel: jfs: jfs_dmap: Validate db_l2nbperpage while mounting
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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Description OSIDB Bzimport 2025-09-15 15:01:32 UTC 
In the Linux kernel, the following vulnerability has been resolved:

jfs: jfs_dmap: Validate db_l2nbperpage while mounting

In jfs_dmap.c at line 381, BLKTODMAP is used to get a logical block
number inside dbFree(). db_l2nbperpage, which is the log2 number of
blocks per page, is passed as an argument to BLKTODMAP which uses it
for shifting.

Syzbot reported a shift out-of-bounds crash because db_l2nbperpage is
too big. This happens because the large value is set without any
validation in dbMount() at line 181.

Thus, make sure that db_l2nbperpage is correct while mounting.

Max number of blocks per page = Page size / Min block size
=> log2(Max num_block per page) = log2(Page size / Min block size)
				= log2(Page size) - log2(Min block size)

=> Max db_l2nbperpage = L2PSIZE - L2MINBLOCKSIZE
Comment 1 Keith Grant 2025-09-15 16:42:14 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025091513-CVE-2023-53222-c1a9@gregkh/T