From mboxrd@z Thu Jan 1 00:00:00 1970 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-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit 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=0 while the anonymous structure has kflag=1 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 field 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 { /* * 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 offset + * 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 = tid; - anon_stack[top++].offset = - cur_offset + member->offset; + anon_stack[top++].offset = cur_offset + + __btf_member_bit_offset(type, member); } } else { name = btf_name_by_offset(btf, member->name_off); if (name && !strcmp(member_name, name)) { if (anon_offset) *anon_offset = cur_offset; + if (member_type) + *member_type = 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, const struct btf_type **pty { const struct btf_type *type = *ptype; const struct btf_member *field; + const struct btf_type *mtype = NULL; struct btf *btf = ctx_btf(ctx); char *fieldname = *pfieldname; int bitoffs = 0; @@ -640,7 +641,7 @@ static int get_bitoffset_of_field(char **pfieldname, const struct btf_type **pty anon_offs = 0; field = 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, const struct btf_type **pty bitoffs += anon_offs; /* Accumulate the bit-offsets of the dot-connected fields */ - if (btf_type_kflag(type)) { + if (btf_type_kflag(mtype)) { bitoffs += BTF_MEMBER_BIT_OFFSET(field->offset); ctx->last_bitsize = 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 = 0; } - type = btf_type_skip_modifiers(btf, field->type, NULL); - if (!type) { - trace_probe_log_err(ctx->offset, BAD_BTF_TID); - return -EINVAL; - } + type = btf_type_skip_modifiers(btf, field->type, NULL); + if (!type) { + trace_probe_log_err(ctx->offset, BAD_BTF_TID); + return -EINVAL; + } if (next) ctx->offset += next - fieldname;