Loop with Unreachable Exit Condition ('Infinite Loop') Affecting kernel-rt-modules-internal package, versions *


Severity

Recommended
medium

Based on Red Hat Enterprise Linux security rating.

Threat Intelligence

EPSS
0.05% (18th percentile)

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  • Snyk IDSNYK-RHEL9-KERNELRTMODULESINTERNAL-8380147
  • published14 Nov 2024
  • disclosed9 Nov 2024

Introduced: 9 Nov 2024

CVE-2024-50250  (opens in a new tab)
CWE-835  (opens in a new tab)

How to fix?

There is no fixed version for RHEL:9 kernel-rt-modules-internal.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-rt-modules-internal package and not the kernel-rt-modules-internal package as distributed by RHEL. See How to fix? for RHEL:9 relevant fixed versions and status.

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.

CVSS Scores

version 3.1