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 4BB2147CC62 for ; Thu, 10 Sep 2026 11:51:42 +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=1789041103; cv=none; b=tsN6yA/NIu0nBLUlaX5Axchc41jpn8RBG+NVeLOofFcHPdkHN+5kRkGBeSqVYwlJrfFMl0RsPxk6FS+l/E6Y6w5pFQbAW0AF0TR5QIxmAc28kfLD/buP8DHIVte4733k/FxlDX8ZAAxxQq5uD2hw1NllUGMVjQn6al4DCCraOfA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789041103; c=relaxed/simple; bh=p9vuj3aQiV8Fo0DZD6Yx8bCQviGJrvsmFOwmpUrERGI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=opP/BYnjzw/5usQ9ZSWhApxK58NgTulkjltPY45ARrB5uEaEExwMAE3mYc7wnBkD4q6U7kdSHqJaLzJ8f80xs0wyuR69cgujpQPC5osZFl/J32pHE4EhuHXpJ/WEPLJOuTYccKg6mTtofUoHLAi0Z0IKwImb/tsMEwCMDmHqE0s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=UdnCVD62; 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="UdnCVD62" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 64DEC1F0089B; Thu, 10 Sep 2026 11:51:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789041102; bh=vZArZ5VoldkBSfUnsUjOw9dEh4wckRnSGF0ijpEw0sY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=UdnCVD620Jdj03IztENRyW4HLaKZ19lMjzbOXFhG81mf5GHDaWBbLZklBJIZesCR2 b/cIwICgJHYRQzAEI9YqdSZQNqo1B1b3jfu/M0/4zl+Tlv18K5VXqdQEe655YAIpAL 6X9/bTN/+f4lwlZrYVRbqRv006hqJsp/Y4YFcYFrr2HFErlLSlPK0lH7jyHbb9AWnI 0cdwqdYnclBB/RtQDByfuIh8TPbDLsj36LnYni84ImQDpTfLNg0wcjkJFIg+8TihQM SqwdRcCPhvDWtO7wvfWJoaKrl2aD7s67c2hgAE4uCc5ynxqXmttCtEaJLiWLzSaKWm SOTePU5v2hHEQ== From: Sasha Levin To: stable@vger.kernel.org Cc: "Masami Hiramatsu (Google)" , Sashiko , Steven Rostedt , Sasha Levin Subject: [PATCH 6.18.y 2/2] tracing/probes: Fix BTF kflag check for anonymous struct member access Date: Thu, 10 Sep 2026 07:51:39 -0400 Message-ID: <20260910115139.111324-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260910115139.111324-1-sashal@kernel.org> References: <2026090849-jawed-juggling-59e4@gregkh> <20260910115139.111324-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: "Masami Hiramatsu (Google)" [ Upstream commit 47e93045a2db80d24f5fef65adecc6b2b32efa23 ] 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(). Link: https://lore.kernel.org/all/178827250904.123716.17452648791331881284.stgit@devnote2/ Fixes: c440adfbe302 ("tracing/probes: Support BTF based data structure field access") Cc: stable@vger.kernel.org Reported-by: Sashiko Closes: https://lore.kernel.org/all/20260822095110.0772E1F000E9@smtp.kernel.org/ Assisted-by: Antigravity:gemini-3.7-flash Signed-off-by: Masami Hiramatsu (Google) Reviewed-by: Steven Rostedt [ applied changes to parse_btf_field() because get_bitoffset_of_field() is absent. ] Signed-off-by: Sasha Levin --- kernel/trace/trace_btf.c | 19 +++++++++++-------- kernel/trace/trace_btf.h | 3 ++- kernel/trace/trace_probe.c | 5 +++-- 3 files changed, 16 insertions(+), 11 deletions(-) diff --git a/kernel/trace/trace_btf.c b/kernel/trace/trace_btf.c index 5bbdbcbbde3cd..807d03ff8f063 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 (btf_type_skip_modifiers(btf, member->type, &tid) && 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 4bc44bc261e6f..4bd26bceae23a 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 813e2ddefdaab..95dcfeede94a0 100644 --- a/kernel/trace/trace_probe.c +++ b/kernel/trace/trace_probe.c @@ -577,6 +577,7 @@ static int parse_btf_field(char *fieldname, const struct btf_type *type, { struct fetch_insn *code = *pcode; const struct btf_member *field; + const struct btf_type *mtype; u32 bitoffs, anon_offs; bool is_struct = ctx->struct_btf != NULL; struct btf *btf = ctx_btf(ctx); @@ -611,7 +612,7 @@ static int parse_btf_field(char *fieldname, const struct btf_type *type, 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); @@ -624,7 +625,7 @@ static int parse_btf_field(char *fieldname, const struct btf_type *type, 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 { -- 2.53.0