CVE-2026-46303: isofs: validate Rock Ridge CE continuation extent against volume size

CVE-2026-46303: isofs: validate Rock Ridge CE continuation extent against volume size

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

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

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

isofs: validate Rock Ridge CE continuation extent against volume size

rock_continue() reads rs->cont_extent verbatim from the Rock Ridge CE
record and passes it to sb_bread() without checking that the block
number is within the mounted ISO 9660 volume.  commit e595447e177b
("[PATCH] rock.c: handle corrupted directories") added cont_offset
and cont_size rejection for the CE continuation but did not validate
the extent block number itself.  commit f54e18f1b831 ("isofs: Fix
infinite looping over CE entries") later capped the CE chain length
at RR_MAX_CE_ENTRIES = 32 but again left the block number unchecked.

With a crafted ISO mounted via udisks2 (desktop optical auto-mount)
or via CAP_SYS_ADMIN mount, rs->cont_extent can therefore point at
an out-of-range block or at blocks belonging to an adjacent
filesystem on the same block device.  sb_bread() on an out-of-range
block returns NULL cleanly via the block layer EIO path, so there
is no memory-safety violation.  For in-range reads of adjacent-
filesystem data, the CE buffer is parsed as Rock Ridge records and
only the text of SL sub-records reaches userspace through
readlink(), which makes the info-leak channel narrow and difficult
to exploit; still, rejecting the malformed CE outright matches the
rejection shape already present in the same function for
cont_offset and cont_size.

Add an ISOFS_SB(sb)->s_nzones bounds check to rock_continue() next
to the existing offset/size rejection, printing the same
corrupted-directory-entry notice.

The Linux kernel CVE team has assigned CVE-2026-46303 to this issue.


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

	Issue introduced in 3.19 with commit f54e18f1b831c92f6512d2eedb224cd63d607d3d and fixed in 5.10.258 with commit 8356fb821016797f5677cbeee5ddc0d32a95b4be
	Issue introduced in 3.19 with commit f54e18f1b831c92f6512d2eedb224cd63d607d3d and fixed in 5.15.209 with commit d582e12378bc1637f337622feef762f53c43fd57
	Issue introduced in 3.19 with commit f54e18f1b831c92f6512d2eedb224cd63d607d3d and fixed in 6.1.175 with commit bf1bc673c587f5ef7e9c09b94aea7c5a7847d4d9
	Issue introduced in 3.19 with commit f54e18f1b831c92f6512d2eedb224cd63d607d3d and fixed in 6.6.140 with commit c9b37c8b73f6368e4750e5ccb0632c380b43c6e5
	Issue introduced in 3.19 with commit f54e18f1b831c92f6512d2eedb224cd63d607d3d and fixed in 6.12.88 with commit 22b36fa081f38ab397c7697f9d539211b51a0cfc
	Issue introduced in 3.19 with commit f54e18f1b831c92f6512d2eedb224cd63d607d3d and fixed in 6.18.30 with commit e69da8eeab74b4f4505024c38a17bce060fe7df8
	Issue introduced in 3.19 with commit f54e18f1b831c92f6512d2eedb224cd63d607d3d and fixed in 7.0.7 with commit ef048470c90bc8c1b8318bb2ce329da9ef64b9fe
	Issue introduced in 3.19 with commit f54e18f1b831c92f6512d2eedb224cd63d607d3d and fixed in 7.1-rc2 with commit a36d990f591320e9dd379ab30063ebfe91d47e1f
	Issue introduced in 2.6.32.66 with commit 08313e26e06d4aa9ce1cbba1a8e359e9cab9ad56
	Issue introduced in 3.2.67 with commit 212c4d33ca83e2144064fe9c2911607fbed5386f
	Issue introduced in 3.4.107 with commit 96e44adce250199ec9b2b928be66365779ff1b59
	Issue introduced in 3.10.64 with commit 1fe5620fcd6c2f0a4a927ee10c8e53196da392f3
	Issue introduced in 3.12.36 with commit fbce0d7dc8965c9fb8d411862040239d4a768c71
	Issue introduced in 3.14.28 with commit 8190393a88f2b0321263a54f2a9eb5a2aa43be7e
	Issue introduced in 3.17.8 with commit 486aa789eadcf44ed87f972b209299c516454693
	Issue introduced in 3.18.2 with commit b6d20edb6e7cedb4eedb9e0193d20dd488ebae84

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-2026-46303
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:
	fs/isofs/rock.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/8356fb821016797f5677cbeee5ddc0d32a95b4be
	https://git.kernel.org/stable/c/d582e12378bc1637f337622feef762f53c43fd57
	https://git.kernel.org/stable/c/bf1bc673c587f5ef7e9c09b94aea7c5a7847d4d9
	https://git.kernel.org/stable/c/c9b37c8b73f6368e4750e5ccb0632c380b43c6e5
	https://git.kernel.org/stable/c/22b36fa081f38ab397c7697f9d539211b51a0cfc
	https://git.kernel.org/stable/c/e69da8eeab74b4f4505024c38a17bce060fe7df8
	https://git.kernel.org/stable/c/ef048470c90bc8c1b8318bb2ce329da9ef64b9fe
	https://git.kernel.org/stable/c/a36d990f591320e9dd379ab30063ebfe91d47e1f