CVE-2024-50250 (GCVE-0-2024-50250)

Vulnerability from cvelistv5 – Published: 2024-11-09 10:14 – Updated: 2025-11-03 22:27
VLAI?
Title
fsdax: dax_unshare_iter needs to copy entire blocks
Summary
In the Linux kernel, the following vulnerability has been resolved: fsdax: dax_unshare_iter needs to copy entire blocks The code that copies data from srcmap to iomap in dax_unshare_iter is very very broken, which bfoster's recent fsx changes have exposed. If the pos and len passed to dax_file_unshare are not aligned to an fsblock boundary, the iter pos and length in the _iter function will reflect this unalignment. dax_iomap_direct_access always returns a pointer to the start of the kmapped fsdax page, even if its pos argument is in the middle of that page. This is catastrophic for data integrity when iter->pos is not aligned to a page, because daddr/saddr do not point to the same byte in the file as iter->pos. Hence we corrupt user data by copying it to the wrong place. If iter->pos + iomap_length() in the _iter function not aligned to a page, then we fail to copy a full block, and only partially populate the destination block. This is catastrophic for data confidentiality because we expose stale pmem contents. Fix both of these issues by aligning copy_pos/copy_len to a page boundary (remember, this is fsdax so 1 fsblock == 1 base page) so that we always copy full blocks. We're not done yet -- there's no call to invalidate_inode_pages2_range, so programs that have the file range mmap'd will continue accessing the old memory mapping after the file metadata updates have completed. Be careful with the return value -- if the unshare succeeds, we still need to return the number of bytes that the iomap iter thinks we're operating on.
Severity ?
7.1 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
CWE
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 1bec6782a25c9b92c203ea7a1b3e3dc6a468cbc4 , < bdbc96c23197d773a7d1bf03e4f11de593b0ff28 (git)
Affected: d984648e428bf88cbd94ebe346c73632cb92fffb , < 9bc18bb476e50e32e5d08f2734d63d63e0fa528c (git)
Affected: d984648e428bf88cbd94ebe346c73632cb92fffb , < 8e9c0f500b42216ef930f5c0d1703989a451913d (git)
Affected: d984648e428bf88cbd94ebe346c73632cb92fffb , < 50793801fc7f6d08def48754fb0f0706b0cfc394 (git)
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    Linux Linux Affected: 6.2
Unaffected: 0 , < 6.2 (semver)
Unaffected: 6.1.116 , ≤ 6.1.* (semver)
Unaffected: 6.6.60 , ≤ 6.6.* (semver)
Unaffected: 6.11.7 , ≤ 6.11.* (semver)
Unaffected: 6.12 , ≤ * (original_commit_for_fix)
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  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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