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Fencer Vulns
high 7.8

CVE-2024-50250 json

fsdax: dax_unshare_iter needs to copy entire blocks

published 2024-11-09 1 y ago modified 2026-08-05 3 mo ago also EUVD-2024-44752

cvss
7.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 13%
public exploits
0
none known

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.

Patch / fix

  • Linux Linux 6.1.116, 6.6.60, 6.11.7, 6.12
  • linux Debian 12 6.1.119-1
  • linux Debian 14, Debian 13 6.11.7-1

debian advisories DEBIAN-CVE-2024-50250

  • linux Ubuntu 24.04 LTS 6.8.0-58.60
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1027.29
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1028.30
  • linux-gke Ubuntu 24.04 LTS 6.8.0-1023.27
  • linux-ibm Ubuntu 24.04 LTS 6.8.0-1024.24
  • linux-azure Ubuntu 24.04 LTS 6.8.0-1027.32
  • linux-gkeop Ubuntu 24.04 LTS 6.8.0-1010.12
  • linux-raspi Ubuntu 24.04 LTS 6.8.0-1028.32

ubuntu advisories UBUNTU-CVE-2024-50250

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel-livepatch-MICRO-6-0_Update_2 Linux Micro 6.1, Linux Micro 6.0 8-1.1
  • kernel-livepatch-MICRO-6-0_Update_3 Linux Micro 6.0 8-1.2
  • kernel-livepatch-MICRO-6-0-RT_Update_2 Linux Micro 6.1, Linux Micro 6.0 8-1.1
  • kernel-livepatch-MICRO-6-0-RT_Update_3 Linux Micro 6.0 8-1.2
  • kernel-source Linux Micro 6.1, Linux Micro 6.0 6.4.0-24.1
  • kernel-default Linux Micro 6.1, Linux Micro 6.0 6.4.0-24.1
  • kernel-kvmsmall Linux Micro 6.1, Linux Micro 6.0 6.4.0-24.1
  • kernel-default-base Linux Micro 6.1, Linux Micro 6.0 6.4.0-24.1.21.4

suse advisories SUSE-SU-2025:20525-1SUSE-SU-2025:20526-1SUSE-SU-2025:20540-1SUSE-SU-2025:20517-1SUSE-SU-2025:20518-1SUSE-SU-2025:20544-1

  • kernel-source-longterm openSUSE Tumbleweed 6.12.11-1.1
  • kernel-source openSUSE Tumbleweed 6.11.8-1.1

opensuse advisories openSUSE-SU-2025:14705-1openSUSE-SU-2024:14500-1

  • kernel Azure Linux 3.0 6.6.64.2-1

azure linux advisories AZL-53373

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2024-50250 updated cvss 7.3

kernel: fsdax: dax_unshare_iter needs to copy entire blocks

  • Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +82 more
    affected: workaround, no fix planned “Will not fix”
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
13 mo ago

Exploit prediction

0.23% chance of exploitation in the next 30 days, higher than 13% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CISA ADP 3.1 7.1 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
NVD 3.1 7.1 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
CNA 3.1 7.1 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.