[PATCH 6.6.y 2/2] bpf: abort verification if env->cur_state->loop_entry != NULL

[Artem Dinaburg <artem@trailofbits.com>]

From: Eduard Zingerman <eddyz87@gmail.com>

[ Upstream commit f3c2d243a36ef23be07bc2bce7c6a5cb6e07d9e3 ]

In addition to warning abort verification with -EFAULT.
If env->cur_state->loop_entry != NULL something is irrecoverably
buggy.

Fixes: bbbc02b7445e ("bpf: copy_verifier_state() should copy 'loop_entry' field")
Suggested-by: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20250225003838.135319-1-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Assisted-by: LLM
Signed-off-by: Artem Dinaburg <artem@trailofbits.com>
---
Hi,

Please consider this backport of the corrective follow-up for
CVE-2025-38060 to 6.6.y.

The code changes are identical to upstream.

The complete fix is already present in 6.12.y, 6.18.y and 7.2.y.

Build-tested only as part of a cumulative 6.6.y series on x86_64
(allmodconfig, CONFIG_WERROR=y); no runtime testing.

Thanks,
Artem Dinaburg

 kernel/bpf/verifier.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index c00113e691955a6c9c6caa56007ccf90ce9b87d8..37abde03f174ef5c0a47317d9b9d19eeaeb0ccd2 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -17562,8 +17562,10 @@ process_bpf_exit:
 						return err;
 					break;
 				} else {
-					if (WARN_ON_ONCE(env->cur_state->loop_entry))
-						env->cur_state->loop_entry = NULL;
+					if (WARN_ON_ONCE(env->cur_state->loop_entry)) {
+						verbose(env, "verifier bug: env->cur_state->loop_entry != NULL\n");
+						return -EFAULT;
+					}
 					do_print_state = true;
 					continue;
 				}