CVE-2026-74350: ocfs2: validate fast symlink target during inode read

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

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

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

ocfs2: validate fast symlink target during inode read

ocfs2_validate_inode_block() already rejects several inconsistent
self-contained dinodes before they are exposed to the rest of the
filesystem.  Fast symlinks need the same treatment.

A zero-cluster symlink is treated as a fast symlink and later read through
page_get_link() and ocfs2_fast_symlink_read_folio().  That path uses
strnlen() on the inline payload and then copies len + 1 bytes into the
folio.  If a corrupt dinode stores an i_size that does not fit the inline
area or omits the terminating NUL at i_size, that copy reads past the end
of the inode block buffer.

Reject zero-cluster symlink dinodes whose i_size exceeds the inline
fast-symlink capacity or whose inline payload is not NUL-terminated
exactly at i_size when the inode block is validated.  This keeps malformed
fast symlinks from reaching the read path.

Validation reproduced this kernel report:
KASAN use-after-free in ocfs2_fast_symlink_read_folio+0x12c/0x1f0
RIP: 0033:0x7f5c6d859aa7
Read of size 3905
Call trace:
  dump_stack_lvl+0x66/0xa0 (?:?)
  print_report+0xce/0x630 (?:?)
  ocfs2_fast_symlink_read_folio+0x12c/0x1f0 (fs/ocfs2/inode.c:?)
  srso_alias_return_thunk+0x5/0xfbef5 (?:?)
  __virt_addr_valid+0x19f/0x330 (?:?)
  kasan_report+0xe0/0x110 (?:?)
  kasan_check_range+0x105/0x1b0 (?:?)
  __asan_memcpy+0x23/0x60 (?:?)
  filemap_read_folio+0x27/0xe0 (?:?)
  filemap_read_folio+0x35/0xe0 (?:?)
  do_read_cache_folio+0x138/0x230 (?:?)
  __page_get_link+0x26/0x110 (?:?)
  page_get_link+0x2e/0x70 (?:?)
  vfs_readlink+0x15e/0x250 (?:?)
  touch_atime+0x4d/0x370 (?:?)
  do_readlinkat+0x186/0x200 (?:?)
  do_user_addr_fault+0x65a/0x890 (?:?)
  __x64_sys_readlink+0x46/0x60 (?:?)
  do_syscall_64+0x115/0x6a0 (arch/x86/entry/syscall_64.c:87)
  entry_SYSCALL_64_after_hwframe+0x77/0x7f (?:?)

The Linux kernel CVE team has assigned CVE-2026-74350 to this issue.


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

	Issue introduced in 3.5 with commit ea022dfb3c2a4680483b00eb2fecc9fc4f6091d1 and fixed in 7.1.5 with commit f9e2cb692b77a679b1f4cc2b7b277fa908586533
	Issue introduced in 3.5 with commit ea022dfb3c2a4680483b00eb2fecc9fc4f6091d1 and fixed in 7.2-rc1 with commit e234973f286ed2e8961a24561ec91594ec3e3ff8

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-2026-74350
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/ocfs2/inode.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/f9e2cb692b77a679b1f4cc2b7b277fa908586533
	https://git.kernel.org/stable/c/e234973f286ed2e8961a24561ec91594ec3e3ff8