Bug 2425016 (CVE-2023-54062)

Summary: CVE-2023-54062 kernel: ext4: fix invalid free tracking in ext4_xattr_move_to_block()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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OS: Linux   
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A memory management flaw was found in the Linux kernel's ext4 filesystem extended attribute handling. In ext4_xattr_move_to_block(), when moving an extended attribute value to an external block, the code checks entry->e_value_inum to determine if the buffer was allocated via kvmalloc(). However, at cleanup time the xattr entry pointer is stale (already removed), leading to either calling kvfree() on an invalid pointer or leaking memory that should have been freed.
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Description OSIDB Bzimport 2025-12-24 13:02:13 UTC 
In the Linux kernel, the following vulnerability has been resolved:

ext4: fix invalid free tracking in ext4_xattr_move_to_block()

In ext4_xattr_move_to_block(), the value of the extended attribute
which we need to move to an external block may be allocated by
kvmalloc() if the value is stored in an external inode.  So at the end
of the function the code tried to check if this was the case by
testing entry->e_value_inum.

However, at this point, the pointer to the xattr entry is no longer
valid, because it was removed from the original location where it had
been stored.  So we could end up calling kvfree() on a pointer which
was not allocated by kvmalloc(); or we could also potentially leak
memory by not freeing the buffer when it should be freed.  Fix this by
storing whether it should be freed in a separate variable.
Comment 1 Alexander B 2025-12-25 08:39:30 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025122428-CVE-2023-54062-d861@gregkh/T