Bug 2535238 (CVE-2026-89830)

Summary: CVE-2026-89830 kernel: f2fs: fix valid block count leak on data block allocation failure
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the f2fs (Flash-Friendly File System) component of the Linux kernel. When the system attempts to allocate new data blocks, it may incorrectly increment the count of valid blocks without properly reversing this action if the allocation process fails. This oversight leads to a permanent leak in the block count tracking. Over time, this resource leak could be exploited by a local attacker to cause a denial of service (DoS) by exhausting available system resources.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-09-16 11:38:43 UTC 
In the Linux kernel, the following vulnerability has been resolved:

f2fs: fix valid block count leak on data block allocation failure

In __allocate_data_block(), when allocating a new data block
(dn->data_blkaddr == NULL_ADDR), inc_valid_block_count() is
called first to increment total_valid_block_count and i_blocks.
If the subsequent f2fs_allocate_data_block() fails, the function
returns the error directly without rolling back the
already-incremented block counts, causing a permanent leak.

Fix this by calling dec_valid_block_count() to undo the
increment before returning the error. The condition
old_blkaddr == NULL_ADDR precisely identifies the case where
inc_valid_block_count() was called.
Comment 1 Mauro Matteo Cascella 2026-09-21 18:00:29 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89830.mbox