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 3684738D3FD; Tue, 1 Sep 2026 14:21:54 +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=1788272516; cv=none; b=eZptBCv0+YRbSpliCQRPi5dhhm3rO0V2GGHcf9GMf7UALG7fecOC14c5wp1AbyODEDsvMRLxkYVEPuWCMHTjgKljZTvHWcAW98k64yii0cP+/w5TVoLtFfDwZspGau9IIOHrqkTIjKE4NQIjKjazj44kL3RL+GT6D2wNC8ZJG/E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788272516; c=relaxed/simple; bh=bcWdDeucekjH4dtjZhbljTqEFVKo/EJ3rtaOnEaeSi4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=sSJq7nfcqlKFfS6mSkL0R6ajRlFq6u7sXKkEq4yp/F09G3mK7dC0xDbJ/u+JC2vxbRlGIxv5Lfo2r3lZYzt/oaHVOPl/BATM1fWdXZgNEsn+OBuvFSzsDmwzkPA5hLPFQdgriwr0cgGhQ+s3UX2yC06miz5YTECV3SDETCMaguc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=RNFQu6Nh; 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="RNFQu6Nh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 66DAC1F000E9; Tue, 1 Sep 2026 14:21:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788272514; bh=N1RSqeA8oOvxj7Rd5uHkQcz2LL1Drv5deATg5L0dJZE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=RNFQu6Nhsybjei7NcY/opgtj12UuxiPq5oyQO3hj2C3TavGsZEmyr1uzIF0kvc0UF JTAfDEhhJ72hDZZQvhQj0nlelzIX04Ufad8SbaYL5e2NnCWWGmnish1sbYGchv43+c Xt9XeGeFpzPdwFMNUBqaJFAZ2lwzlir32e9xXyKzE4O5DuxTBU8szllNqn2ay2k8yg GTSvkx/EGwYUxy1ZVKTSUi3T9QTSATIQYHjPTTzP8MrlDnkGzBPXMX6wzD99EPrWMR rbAg5FYIvzpjtdX3WpmqakpIlamMwu8fxAvVRWhxdQmxZHKOpSeckYDDs+C1vcLM4U TnNc30Iuvkm/Q== 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 v3 2/3] tracing/probes: Fix BTF kflag check for anonymous struct member access Date: Tue, 1 Sep 2026 23:21:49 +0900 Message-ID: <178827250904.123716.17452648791331881284.stgit@devnote2> X-Mailer: git-send-email 2.43.0 In-Reply-To: <178827248631.123716.2627172171811720261.stgit@devnote2> References: <178827248631.123716.2627172171811720261.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") 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) --- Changes in v3: - Remove indent cleanup part since that is a cleanup and no need to be backported. Changes in v2: - remove unneeded NULL initializer for mtype, it should be set if btf_find_struct_member() succeeds. - Add reported-by from Sashiko. 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 | 5 +++-- 3 files changed, 16 insertions(+), 11 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..144e790077c6 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; 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 {