CVE-2026-74338: bpf: Reject sleepable BPF_LSM_CGROUP programs at load time

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

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

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

bpf: Reject sleepable BPF_LSM_CGROUP programs at load time

The cgroup shim runs under rcu_read_lock_dont_migrate(), so we should
not attach any sleepable BPF programs there. Add support to the verifier
to explicitly reject attempts to load sleepable BPF programs destined
for LSM cgroup attachment.

Without this, we get the following splat from a BPF_LSM_CGROUP
program marked BPF_F_SLEEPABLE attached to file_open when it calls
bpf_get_dentry_xattr():

  BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:1567
  in_atomic(): 0, irqs_disabled(): 0, non_block: 0, pid: 34317, name: load
  preempt_count: 0, expected: 0
  RCU nest depth: 2, expected: 0
  Call Trace:
   down_read+0x76/0x480
   ext4_xattr_get+0x11f/0x700
   __vfs_getxattr+0xf0/0x150
   bpf_get_dentry_xattr+0xbb/0xf0
   bpf_prog_e76a298dac9218c6_test_open+0x6a/0x85
   __cgroup_bpf_run_lsm_current+0x326/0x840
   bpf_trampoline_6442534646+0x62/0x14d
   security_file_open+0x34/0x60
   do_dentry_open+0x340/0x1260
   vfs_open+0x7a/0x440
   path_openat+0x1bac/0x30a0

libbpf provides a .s named section variant for every sleepable
program type except lsm_cgroup, reflecting that per-cgroup LSM programs
are intended to only run in a non-sleepable context.

The above splat was obtained by bypassing libbpf by using bpf(2)
directly.

The Linux kernel CVE team has assigned CVE-2026-74338 to this issue.


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

	Issue introduced in 6.0 with commit 69fd337a975c7e690dfe49d9cb4fe5ba1e6db44e and fixed in 7.1.5 with commit be9eaf2bb5db4ad3de61ef739fd268fd7f135737
	Issue introduced in 6.0 with commit 69fd337a975c7e690dfe49d9cb4fe5ba1e6db44e and fixed in 7.2-rc1 with commit 5b038319be442c620f774e6fc9e9283deeca1c75

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-2026-74338
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:
	kernel/bpf/verifier.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/be9eaf2bb5db4ad3de61ef739fd268fd7f135737
	https://git.kernel.org/stable/c/5b038319be442c620f774e6fc9e9283deeca1c75