CVE-2024-50250: fsdax: dax_unshare_iter needs to copy entire blocks
First published: Sat Nov 09 2024(Updated: )
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.
Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Linux Kernel | >=6.1.113<6.1.116 | |
| Linux Kernel | >=6.2<6.6.60 | |
| Linux Kernel | >=6.7<6.11.7 | |
| Linux Kernel | =6.12-rc1 | |
| Linux Kernel | =6.12-rc2 | |
| Linux Kernel | =6.12-rc3 | |
| Linux Kernel | =6.12-rc4 | |
| Linux Kernel | =6.12-rc5 | |
| debian/linux | 5.10.223-1 5.10.234-1 6.1.129-1 6.1.133-1 6.12.21-1 6.12.22-1 | |
| debian/linux-6.1 | 6.1.129-1~deb11u1 |
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Reference Links
- 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
- https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-50250
- https://nvd.nist.gov/vuln/detail/CVE-2024-50250
- https://launchpad.net/bugs/cve/CVE-2024-50250
- https://security-tracker.debian.org/tracker/CVE-2024-50250
- https://ubuntu.com/security/CVE-2024-50250
- https://git.kernel.org/linus/50793801fc7f6d08def48754fb0f0706b0cfc394
Frequently Asked Questions
What is the severity of CVE-2024-50250?
CVE-2024-50250 has a high severity due to its impact on data integrity in the Linux kernel.
How do I fix CVE-2024-50250?
To fix CVE-2024-50250, update your Linux kernel to a version that has patched the vulnerability.
Which versions of the Linux kernel are affected by CVE-2024-50250?
CVE-2024-50250 affects specific versions of the Linux kernel, including from 6.1.113 to 6.1.116 and various versions from 6.2 to 6.12-rc5.
What components does CVE-2024-50250 specific impact?
CVE-2024-50250 specifically impacts the fsdax subsystem within the Linux kernel.
What type of vulnerability is CVE-2024-50250?
CVE-2024-50250 is an integrity vulnerability that arises from broken data copying mechanisms within the Linux kernel.
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