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.
Metrics
Affected Vendors & Products
References
History
Fri, 22 Nov 2024 15:45:00 +0000
Type | Values Removed | Values Added |
---|---|---|
Weaknesses | CWE-835 |
Thu, 14 Nov 2024 17:30:00 +0000
Type | Values Removed | Values Added |
---|---|---|
First Time appeared |
Linux
Linux linux Kernel |
|
Weaknesses | NVD-CWE-noinfo | |
CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.12:rc1:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.12:rc2:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.12:rc3:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.12:rc4:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:6.12:rc5:*:*:*:*:*:* |
|
Vendors & Products |
Linux
Linux linux Kernel |
|
Metrics |
cvssV3_1
|
cvssV3_1
|
Tue, 12 Nov 2024 01:45:00 +0000
Type | Values Removed | Values Added |
---|---|---|
References |
| |
Metrics |
threat_severity
|
cvssV3_1
|
Sat, 09 Nov 2024 10:30:00 +0000
Type | Values Removed | Values Added |
---|---|---|
Description | 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. | |
Title | fsdax: dax_unshare_iter needs to copy entire blocks | |
References |
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published: 2024-11-09T10:14:59.003Z
Updated: 2024-12-19T09:36:32.859Z
Reserved: 2024-10-21T19:36:19.979Z
Link: CVE-2024-50250
Vulnrichment
No data.
NVD
Status : Analyzed
Published: 2024-11-09T11:15:10.833
Modified: 2024-11-14T17:04:14.043
Link: CVE-2024-50250
Redhat