CVE-2026-64317: isofs: bound Rock Ridge symlink components to the SL record

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

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

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

isofs: bound Rock Ridge symlink components to the SL record

get_symlink_chunk() and the SL handling in
parse_rock_ridge_inode_internal() walk the variable-length components of
a Rock Ridge "SL" (symbolic link) record.  Each component is a two-byte
header (flags, len) followed by len bytes of text, so it occupies
slp->len + 2 bytes.  Both loops read slp->len and advance to the next
component, and get_symlink_chunk() additionally does
memcpy(rpnt, slp->text, slp->len), but neither checks that the component
lies within the SL record before dereferencing it.

A crafted SL record whose component declares a len that runs past the
record (rr->len) therefore triggers an out-of-bounds read of up to 255
bytes.  When the record sits at the tail of its backing buffer - for
example a small kmalloc()ed continuation block reached through a CE
record - the read crosses the allocation; get_symlink_chunk() then
copies the out-of-bounds bytes into the symlink body returned to user
space by readlink(), disclosing adjacent kernel memory.

ISO 9660 images are routinely mounted from untrusted removable media -
desktop environments auto-mount them (e.g. via udisks2) without
CAP_SYS_ADMIN - so the record contents are attacker-controlled.

Reject any component that does not fit in the remaining record bytes
before using it.  In get_symlink_chunk() return NULL, like the existing
output-buffer (plimit) checks, so a malformed record makes readlink()
fail with -EIO rather than silently returning a truncated target; in
parse_rock_ridge_inode_internal() stop the inode-size walk.

The Linux kernel CVE team has assigned CVE-2026-64317 to this issue.


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

	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 5.10.261 with commit 1015e1c4b2fadd9c09704e24738e46598778c869
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 5.15.212 with commit 36fe7d25dbc40da0c6b1dd4513a4f69ac6164eee
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.1.178 with commit a22cb6bb54dc167047ea9e70d97dfbc2c15649e3
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.6.145 with commit b736b12108fd116c41777628f5a333791604df26
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.12.96 with commit 6bf41db09ef935d76fcc84ccf213b42c18de95ee
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 6.18.39 with commit b5699642640d6cff357638738c5293985cd5a53d
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 7.1.4 with commit 9830725078c8483c6831ec10222ae724806ea36b
	Issue introduced in 2.6.12 with commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and fixed in 7.2-rc1 with commit 5fa1d6a5ec2356d2107dead614437c66fa7138b1

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-2026-64317
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/1015e1c4b2fadd9c09704e24738e46598778c869
	https://git.kernel.org/stable/c/36fe7d25dbc40da0c6b1dd4513a4f69ac6164eee
	https://git.kernel.org/stable/c/a22cb6bb54dc167047ea9e70d97dfbc2c15649e3
	https://git.kernel.org/stable/c/b736b12108fd116c41777628f5a333791604df26
	https://git.kernel.org/stable/c/6bf41db09ef935d76fcc84ccf213b42c18de95ee
	https://git.kernel.org/stable/c/b5699642640d6cff357638738c5293985cd5a53d
	https://git.kernel.org/stable/c/9830725078c8483c6831ec10222ae724806ea36b
	https://git.kernel.org/stable/c/5fa1d6a5ec2356d2107dead614437c66fa7138b1