FAILED: patch "[PATCH] tracing/probes: Fix anon_stack check for unnamed bitfields in" failed to apply to 6.18-stable tree

The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x f36d94a20ca185bcadef3a10b980cd2cfd72d53a
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026090810-jasmine-divided-a4e9@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From f36d94a20ca185bcadef3a10b980cd2cfd72d53a Mon Sep 17 00:00:00 2001
From: "Masami Hiramatsu (Google)" <[email protected]>
Date: Tue, 1 Sep 2026 23:21:37 +0900
Subject: [PATCH] tracing/probes: Fix anon_stack check for unnamed bitfields in
btf_find_struct_member

btf_find_struct_member() traverses into nested anonymous structures and unions by pushing members with !member->name_off onto anon_stack. However, it does not consider the unnamed bitfields (e.g. int : 5 or unsigned int : 0) which also have member->name_off == 0.

If such an unnamed bitfield is pushed to anon_stack, the btf_find_struct_member() return an error even if there are other valid entries in anon_stack.

To fix this, only push unnamed struct/union members to anon_stack. Also move the btf_type_is_struct() check to the entry of this function because now it is sure only struct/union are pushed to anon_stack.

index 00172f301f25..d3ba356d5503 100644
@@ -74,24 +74,24 @@ const struct btf_member *btf_find_struct_member(struct btf *btf,
 {
 	struct btf_anon_stack *anon_stack;
 	const struct btf_member *member;
+	const struct btf_type *mtype;
 	u32 tid, cur_offset = 0;
 	const char *name;
 	int i, top = 0;
 
+	if (!btf_type_is_struct(type))
+		return ERR_PTR(-EINVAL);
+
 	anon_stack = kzalloc_objs(*anon_stack, BTF_ANON_STACK_MAX);
 	if (!anon_stack)
 		return ERR_PTR(-ENOMEM);
 
 retry:
-	if (!btf_type_is_struct(type)) {
-		member = ERR_PTR(-EINVAL);
-		goto out;
-	}
-
 	for_each_member(i, type, member) {
 		if (!member->name_off) {
 			/* Anonymous union/struct: push it for later use */
-			if (btf_type_skip_modifiers(btf, member->type, &tid) &&
+			mtype = btf_type_skip_modifiers(btf, member->type, &tid);
+			if (mtype && btf_type_is_struct(mtype) &&
 			    top < BTF_ANON_STACK_MAX) {
 				anon_stack[top].tid = tid;
 				anon_stack[top++].offset =

From: "Masami Hiramatsu (Google)" <[email protected]>

[ Upstream commit f36d94a20ca185bcadef3a10b980cd2cfd72d53a ]

btf_find_struct_member() traverses into nested anonymous structures and unions by pushing members with !member->name_off onto anon_stack. However, it does not consider the unnamed bitfields (e.g. int : 5 or unsigned int : 0) which also have member->name_off == 0.

If such an unnamed bitfield is pushed to anon_stack, the btf_find_struct_member() return an error even if there are other valid entries in anon_stack.

To fix this, only push unnamed struct/union members to anon_stack. Also move the btf_type_is_struct() check to the entry of this function because now it is sure only struct/union are pushed to anon_stack.

---
 kernel/trace/trace_btf.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

index 5bbdbcbbde3cd..40e66eb59abbc 100644
@@ -74,24 +74,24 @@ const struct btf_member *btf_find_struct_member(struct btf *btf,
 {
 	struct btf_anon_stack *anon_stack;
 	const struct btf_member *member;
+	const struct btf_type *mtype;
 	u32 tid, cur_offset = 0;
 	const char *name;
 	int i, top = 0;
 
+	if (!btf_type_is_struct(type))
+		return ERR_PTR(-EINVAL);
+
 	anon_stack = kcalloc(BTF_ANON_STACK_MAX, sizeof(*anon_stack), GFP_KERNEL);
 	if (!anon_stack)
 		return ERR_PTR(-ENOMEM);
 
 retry:
-	if (!btf_type_is_struct(type)) {
-		member = ERR_PTR(-EINVAL);
-		goto out;
-	}
-
 	for_each_member(i, type, member) {
 		if (!member->name_off) {
 			/* Anonymous union/struct: push it for later use */
-			if (btf_type_skip_modifiers(btf, member->type, &tid) &&
+			mtype = btf_type_skip_modifiers(btf, member->type, &tid);
+			if (mtype && btf_type_is_struct(mtype) &&
 			    top < BTF_ANON_STACK_MAX) {
 				anon_stack[top].tid = tid;
 				anon_stack[top++].offset =

2.53.0