From nobody Sat Sep 26 15:34:44 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0D7FC2DC350; Mon, 31 Aug 2026 15:06:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788188772; cv=none; b=RliIYyxMoEcsxgruDOglyroZqQQ3m+2BhDG0qWv4ZT42MchAyiPJrFqA1VYs5MC1HqW1tkpiFrZ+USxQNXPhzpuMv+nw9nLihgBxTrl70JTarTW32IsU+oXa+R5zMJs+xYKMtuRQSYwYI5LJ2MxVAoIebm4LumDbemPGWqQUfW4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788188772; c=relaxed/simple; bh=fdxL3/nrOfNKfBh5WixTsa1QP78CyHXEXKRDMHrhFyY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=NX24CqNv5HE2tYaejUBWjkmXF9A2BUjcvkqj0VMlVW4sbVjkisCbTspgLRNEtbLyg0uF7b73a3kEC0NsGOLq6ZIXvE63ywgkcwJu+i6WH9ZcJv1uVTH2vXQQuQkvQ0aTIw+dl7iols4es6iM8lonJ+IJq2gRXzOzaWB+ok3QkI8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=NEZdCdNC; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="NEZdCdNC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 96E2C1F000E9; Mon, 31 Aug 2026 15:06:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788188770; bh=kLPL7I20R8rtDA3Pf0Fn/tayK+z7L1PaWVETTPzhf/A=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=NEZdCdNC+HjgR+zwFDjVw4xmBMyez86tDoHl3yd0ZQbcz6LybEz+4ET4kA78EBz7d p6UUreyKNOMS/tTN6cvNOHY4z6j1k9n3R7HmfBX/cpnBV5/nfzosqNYNAFBYdy/t7g igXt3UhgiCBIPv9wTWpEteyDAS23Gs6HaCVkHgFsxOLYO0Dt6F0Oda3pnXSemn4Rt3 wmch3Ur0yt3JRsGIyYHTIQFkB7gGlLXqKmuswC9mnwUIWorwkaE8e+4uZX2CWj56d6 Fq39ynBOZKTcAF+yl6MKmSwWBDWeBegsaoL5yOpJVkoAh5DT7Xy0CdYt/GAY9sAhQ9 WvYc+SGaWhxHg== From: "Masami Hiramatsu (Google)" To: Steven Rostedt , Peter Zijlstra , Ingo Molnar , x86@kernel.org Cc: Jinchao Wang , Mathieu Desnoyers , Masami Hiramatsu , Thomas Gleixner , Borislav Petkov , Dave Hansen , "H . Peter Anvin" , Alexander Shishkin , Ian Rogers , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-perf-users@vger.kernel.org Subject: [PATCH 1/2] tracing/probes: Fix anon_stack check for unnamed bitfields in btf_find_struct_member Date: Tue, 1 Sep 2026 00:06:05 +0900 Message-ID: <178818876548.104360.13229872396750615226.stgit@devnote2> X-Mailer: git-send-email 2.43.0 In-Reply-To: <178818875393.104360.1469039168635349344.stgit@devnote2> References: <178818875393.104360.1469039168635349344.stgit@devnote2> User-Agent: StGit/0.19 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable From: Masami Hiramatsu (Google) 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 =3D=3D 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. Fixes: 302db0f5b3d8 ("tracing/probes: Add a function to search a member of = a struct/union") Signed-off-by: Masami Hiramatsu (Google) Reviewed-by: Steven Rostedt --- kernel/trace/trace_btf.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/kernel/trace/trace_btf.c b/kernel/trace/trace_btf.c index 00172f301f25..d3ba356d5503 100644 --- a/kernel/trace/trace_btf.c +++ b/kernel/trace/trace_btf.c @@ -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 =3D 0; const char *name; int i, top =3D 0; =20 + if (!btf_type_is_struct(type)) + return ERR_PTR(-EINVAL); + anon_stack =3D kzalloc_objs(*anon_stack, BTF_ANON_STACK_MAX); if (!anon_stack) return ERR_PTR(-ENOMEM); =20 retry: - if (!btf_type_is_struct(type)) { - member =3D 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 =3D btf_type_skip_modifiers(btf, member->type, &tid); + if (mtype && btf_type_is_struct(mtype) && top < BTF_ANON_STACK_MAX) { anon_stack[top].tid =3D tid; anon_stack[top++].offset =3D From nobody Sat Sep 26 15:34:44 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D39962DC350; Mon, 31 Aug 2026 15:06:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788188784; cv=none; b=luFvKefC0TQgccexcOn6kqUwmKhZTKYHxaq8FfaSqywpAmh0jCz9GZ6cvF+gjU7ijEEPAtDipVHFBHGzzm1RSOl1mlHbFs3OpqGlMmu/tuwqnrkd9mOi1deOSOJnzrm2HZYlEnaS+8P0DbVmIsQGp+KokDomQ7X/oswnhovh4Ck= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788188784; c=relaxed/simple; bh=ibu6LZ3BEKxiIYE0JR0hwUHZH7jDp2GIKjMpj5TaW5c=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=t/jL83BRnJAmv0tEGb/fPxdpubRBJ0TSN6HEj9WHKAFO0l9eCX3wXOPKGkAnkELniPUcVL9+259oFBau6jO49Gzlciq4E29ugvMcHh9Dha2qm3lrtEwZcdkgKPFA2DoEi6FA+o02NOMEe3fxMkpg+aYwjB/KpmxQ/NGYM6+a/ds= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=nDKTIion; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="nDKTIion" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D73EE1F000E9; Mon, 31 Aug 2026 15:06:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788188782; bh=6Edu64T4weJ/kJ+tb2++5BsIaJvIAnxDYHi6GHU8kAs=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=nDKTIiony1RVHKlAZ83702w3rW5M8ZPhvIOGrgqdevy9wBkmVih6d5XJmbSFRcOqw UIZ4df9stNAhWqOlHwS59rXYG3YrgErOB2/LeeF4Lxnn7Pv1G62yGqwbscrW8wFu7C mqtQ9n+sG8cI+i2km4WCV+1AfafRv9/YcAG52SclxUYwBLMEZK3mHb/D623zZrJHnu cTnIyWdRDl9ziMW9lyzBLpFq5fMCC2+WgDCyqcxEgpqQPj7rB1yUTt4aT9V5RGLTCh yfmEcK2EFqaId19ioxTstPaeaulfFmwoANAmBVuzNVBCeK7Mdo71R6qVch0uui+Z4W Mg6WvKZ+V4rPg== From: "Masami Hiramatsu (Google)" To: Steven Rostedt , Peter Zijlstra , Ingo Molnar , x86@kernel.org Cc: Jinchao Wang , Mathieu Desnoyers , Masami Hiramatsu , Thomas Gleixner , Borislav Petkov , Dave Hansen , "H . Peter Anvin" , Alexander Shishkin , Ian Rogers , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-perf-users@vger.kernel.org Subject: [PATCH 2/2] tracing/probes: Fix BTF kflag check for anonymous struct member access Date: Tue, 1 Sep 2026 00:06:16 +0900 Message-ID: <178818877624.104360.10938474138218043559.stgit@devnote2> X-Mailer: git-send-email 2.43.0 In-Reply-To: <178818875393.104360.1469039168635349344.stgit@devnote2> References: <178818875393.104360.1469039168635349344.stgit@devnote2> User-Agent: StGit/0.19 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable From: Masami Hiramatsu (Google) btf_find_struct_member() traverses into nested anonymous structures and unions to find a struct member. However, get_bitoffset_of_field() in trace_probe.c checked btf_type_kflag(type) using the outer parent type instead of the actual anonymous structure/union that directly contains the found member. If the parent structure and anonymous structure have mismatched kflags (e.g., the parent has kflag=3D0 while the anonymous structure has kflag=3D1 because it contains bitfields), the bitfield size encoded in the upper 8 bits of member->offset is erroneously treated as part of the byte/bit offset, corrupting the resolved offset and failing to set last_bitsize. Similarly, btf_find_struct_member() pushed anonymous member offsets onto anon_stack without masking BTF_MEMBER_BIT_OFFSET() when kflag is set. To fix this problem, update btf_find_struct_member() to return actual containing structure/union type via member_type, use appropriate __btf_member_bit_offset() to get bit offset, and use member_type for btf_type_kflag() in get_bitoffset_of_field(). Fixes: c440adfbe302 ("tracing/probes: Support BTF based data structure fiel= d access") Assisted-by: Antigravity:gemini-3.7-flash Signed-off-by: Masami Hiramatsu (Google) --- This is separated from wprobe patch series v14. - https://lore.kernel.org/all/178810003326.64882.5820404025124695636.stgit= @devnote2/ --- kernel/trace/trace_btf.c | 19 +++++++++++-------- kernel/trace/trace_btf.h | 3 ++- kernel/trace/trace_probe.c | 15 ++++++++------- 3 files changed, 21 insertions(+), 16 deletions(-) diff --git a/kernel/trace/trace_btf.c b/kernel/trace/trace_btf.c index d3ba356d5503..ee7a04886bf6 100644 --- a/kernel/trace/trace_btf.c +++ b/kernel/trace/trace_btf.c @@ -61,16 +61,17 @@ struct btf_anon_stack { =20 /* * Find a member of data structure/union by name and return it. - * Return NULL if not found, or -EINVAL if parameter is invalid. - * If the member is an member of anonymous union/structure, the offset - * of that anonymous union/structure is stored into @anon_offset. Caller - * can calculate the correct offset from the root data structure by - * adding anon_offset to the member's offset. + * Return NULL if not found, or ERR_PTR(-EINVAL) if parameter is invalid. + * If the member is a member of an anonymous union/structure, the bit offs= et + * of that anonymous union/structure is stored into @anon_offset. + * If @member_type is non-NULL, the actual containing structure/union type + * of the found member is stored into @member_type. */ const struct btf_member *btf_find_struct_member(struct btf *btf, const struct btf_type *type, const char *member_name, - u32 *anon_offset) + u32 *anon_offset, + const struct btf_type **member_type) { struct btf_anon_stack *anon_stack; const struct btf_member *member; @@ -94,14 +95,16 @@ const struct btf_member *btf_find_struct_member(struct = btf *btf, if (mtype && btf_type_is_struct(mtype) && top < BTF_ANON_STACK_MAX) { anon_stack[top].tid =3D tid; - anon_stack[top++].offset =3D - cur_offset + member->offset; + anon_stack[top++].offset =3D cur_offset + + __btf_member_bit_offset(type, member); } } else { name =3D btf_name_by_offset(btf, member->name_off); if (name && !strcmp(member_name, name)) { if (anon_offset) *anon_offset =3D cur_offset; + if (member_type) + *member_type =3D type; goto out; } } diff --git a/kernel/trace/trace_btf.h b/kernel/trace/trace_btf.h index 4bc44bc261e6..4bd26bceae23 100644 --- a/kernel/trace/trace_btf.h +++ b/kernel/trace/trace_btf.h @@ -8,4 +8,5 @@ const struct btf_param *btf_get_func_param(const struct btf= _type *func_proto, const struct btf_member *btf_find_struct_member(struct btf *btf, const struct btf_type *type, const char *member_name, - u32 *anon_offset); + u32 *anon_offset, + const struct btf_type **member_type); diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c index c4163904ba74..ce2a7bb00d28 100644 --- a/kernel/trace/trace_probe.c +++ b/kernel/trace/trace_probe.c @@ -625,6 +625,7 @@ static int get_bitoffset_of_field(char **pfieldname, co= nst struct btf_type **pty { const struct btf_type *type =3D *ptype; const struct btf_member *field; + const struct btf_type *mtype =3D NULL; struct btf *btf =3D ctx_btf(ctx); char *fieldname =3D *pfieldname; int bitoffs =3D 0; @@ -640,7 +641,7 @@ static int get_bitoffset_of_field(char **pfieldname, co= nst struct btf_type **pty =20 anon_offs =3D 0; field =3D btf_find_struct_member(btf, type, fieldname, - &anon_offs); + &anon_offs, &mtype); if (IS_ERR(field)) { trace_probe_log_err(ctx->offset, BAD_BTF_TID); return PTR_ERR(field); @@ -653,7 +654,7 @@ static int get_bitoffset_of_field(char **pfieldname, co= nst struct btf_type **pty bitoffs +=3D anon_offs; =20 /* Accumulate the bit-offsets of the dot-connected fields */ - if (btf_type_kflag(type)) { + if (btf_type_kflag(mtype)) { bitoffs +=3D BTF_MEMBER_BIT_OFFSET(field->offset); ctx->last_bitsize =3D BTF_MEMBER_BITFIELD_SIZE(field->offset); } else { @@ -661,11 +662,11 @@ static int get_bitoffset_of_field(char **pfieldname, = const struct btf_type **pty ctx->last_bitsize =3D 0; } =20 - type =3D btf_type_skip_modifiers(btf, field->type, NULL); - if (!type) { - trace_probe_log_err(ctx->offset, BAD_BTF_TID); - return -EINVAL; - } + type =3D btf_type_skip_modifiers(btf, field->type, NULL); + if (!type) { + trace_probe_log_err(ctx->offset, BAD_BTF_TID); + return -EINVAL; + } =20 if (next) ctx->offset +=3D next - fieldname;