Description (CNA)
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.
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected 1bec6782a25c9b92c203ea7a1b3e3dc6a468cbc4 before bdbc96c23197d773a7d1bf03e4f11de593b0ff28; affected d984648e428bf88cbd94ebe346c73632cb92fffb before 9bc18bb476e50e32e5d08f2734d63d63e0fa528c; affected d984648e428bf88cbd94ebe346c73632cb92fffb before 8e9c0f500b42216ef930f5c0d1703989a451913d; affected d984648e428bf88cbd94ebe346c73632cb92fffb before 50793801fc7f6d08def48754fb0f0706b0cfc394; affected 6.1.113 before 6.1.116 |
| Linux / Linux | affected 6.2; unaffected 0 before 6.2; unaffected 6.1.116 through 6.1.*; unaffected 6.6.60 through 6.6.*; unaffected 6.11.7 through 6.11.*; unaffected 6.12 through * |
CWE
No CWE identifiers supplied.
References
- https://git.kernel.org/stable/c/bdbc96c23197d773a7d1bf03e4f11de593b0ff28
- https://git.kernel.org/stable/c/9bc18bb476e50e32e5d08f2734d63d63e0fa528c
- https://git.kernel.org/stable/c/8e9c0f500b42216ef930f5c0d1703989a451913d
- https://git.kernel.org/stable/c/50793801fc7f6d08def48754fb0f0706b0cfc394
ADP enrichment
No English description supplied.
No references supplied.
No English description supplied.