CVE-2026-72107: dm era: fix out-of-bounds memory access for non-zero start sector

From: Greg Kroah-Hartman <[email protected]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

dm era: fix out-of-bounds memory access for non-zero start sector

dm-era tracks writes in target-relative blocks, but era_map() calculates
the writeset block before applying the target offset.  Tables with a
non-zero start sector can therefore pass an absolute mapped-device block
to metadata_current_marked().

If the absolute block is beyond the current writeset size,
writeset_marked() tests past the end of the in-core bitset.  KASAN reports
this as a vmalloc-out-of-bounds access.

Apply the target offset before calculating the era block so writeset
lookups use the target-relative block number.

The Linux kernel CVE team has assigned CVE-2026-72107 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 3.15 with commit eec40579d84873dfb7021eb24c50360f073237c5 and fixed in 5.10.261 with commit fe94a0b14010a3c267ff9a2508afb4f27ff1c5bf
	Issue introduced in 3.15 with commit eec40579d84873dfb7021eb24c50360f073237c5 and fixed in 5.15.212 with commit e3ffa8e492e5cdee62d916ee3e9244ccce2b73c5
	Issue introduced in 3.15 with commit eec40579d84873dfb7021eb24c50360f073237c5 and fixed in 6.1.178 with commit 9946a7176bd8c25ddd6e5f1799c54e572ee6bf0f
	Issue introduced in 3.15 with commit eec40579d84873dfb7021eb24c50360f073237c5 and fixed in 6.6.145 with commit 7e1822f83c5a1ee7b4a19e98edde8770a10b4c71
	Issue introduced in 3.15 with commit eec40579d84873dfb7021eb24c50360f073237c5 and fixed in 6.12.97 with commit db5f9b4601f0012038e5a2628aedec2f47933380
	Issue introduced in 3.15 with commit eec40579d84873dfb7021eb24c50360f073237c5 and fixed in 6.18.40 with commit 1fcb5e29dd7a5b85adb9d8b539911741d878e829
	Issue introduced in 3.15 with commit eec40579d84873dfb7021eb24c50360f073237c5 and fixed in 7.1.5 with commit bafe3e720cdac38cd7ea4eb7852a8f2dbe1bbfe6
	Issue introduced in 3.15 with commit eec40579d84873dfb7021eb24c50360f073237c5 and fixed in 7.2-rc3 with commit a868196f03c2b19418ae3d2b69e195d668a271e5

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-72107
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/md/dm-era-target.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/fe94a0b14010a3c267ff9a2508afb4f27ff1c5bf
	https://git.kernel.org/stable/c/e3ffa8e492e5cdee62d916ee3e9244ccce2b73c5
	https://git.kernel.org/stable/c/9946a7176bd8c25ddd6e5f1799c54e572ee6bf0f
	https://git.kernel.org/stable/c/7e1822f83c5a1ee7b4a19e98edde8770a10b4c71
	https://git.kernel.org/stable/c/db5f9b4601f0012038e5a2628aedec2f47933380
	https://git.kernel.org/stable/c/1fcb5e29dd7a5b85adb9d8b539911741d878e829
	https://git.kernel.org/stable/c/bafe3e720cdac38cd7ea4eb7852a8f2dbe1bbfe6
	https://git.kernel.org/stable/c/a868196f03c2b19418ae3d2b69e195d668a271e5