From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-178.mta1.migadu.com (out-178.mta1.migadu.com [95.215.58.178]) (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 0FA7133893D for ; Fri, 5 Jun 2026 15:53:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780674826; cv=none; b=elGa7cqr4s2O3fKw1E8oVduLA320dp5HNjCEi0U+og8+TSr5j6G8JFim3zZzbtVKt4NSVUmyYWQ6umyu3zF1MGBJ5LWiGsv7yINJeQfBg3ChBru+Xo5ouUzCZ/9gdt/Igpd0slsnM9KotjThfS+utu9BpIOUu6RFr8Sl08OwV2s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780674826; c=relaxed/simple; bh=/eRNs/ogIIaKVyWyFlMBj4uvfykEa3kuZQ9piENK1HY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Y2RwmDwfv9G3aRxgnWMkTH3QgrH9y/8WtjaGM7KRPfDQj0jVNkE0DRp9HMz+CJ2loTGPqHZ1U59jubUHdO46rzCUi16hp3tT1eUJ/6X3NLqyUun9wRIOPrV92AXkBS9FnVJBVbiZkKRasKUHe2j5D2cdeIc7YcIjrQvGClm2jPk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=FUelMOxN; arc=none smtp.client-ip=95.215.58.178 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="FUelMOxN" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1780674823; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ejoApRDr1nYqC2TLGz3CjwySzcrXPnhgjJK5sQw/7I4=; b=FUelMOxNDA3Vxtz4qala2bE3P46Zz15ScWMTqktSjNIU8QCbS5bGc6M25DZl1p3M4RnpUg uyw9gRHcMNJnqLK1nZEzq4+JWmHc6f+ME0dEPF3EasaVnjg+x9y983D5sMw+IVXXpbC70V wD/Mj8D32JXhPQsyrmt0bYSaKpelZEA= From: Leon Hwang To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Kumar Kartikeya Dwivedi , Song Liu , Yonghong Song , Jiri Olsa , Shuah Khan , Yuyang Huang , Leon Hwang , KP Singh , Dave Marchevsky , Stanislav Fomichev , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, kernel-patches-bot@fb.com, Mykyta Yatsenko Subject: [PATCH bpf-next v3 1/3] bpf: Check tail zero of bpf_map_info Date: Fri, 5 Jun 2026 23:52:47 +0800 Message-ID: <20260605155249.20772-2-leon.hwang@linux.dev> In-Reply-To: <20260605155249.20772-1-leon.hwang@linux.dev> References: <20260605155249.20772-1-leon.hwang@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT Since there're 4 bytes padding at the end of struct bpf_map_info, they won't be checked by bpf_check_uarg_tail_zero(). pahole -C bpf_map_info ./vmlinux struct bpf_map_info { ... __u64 hash __attribute__((__aligned__(8))); /* 88 8 */ __u32 hash_size; /* 96 4 */ /* size: 104, cachelines: 2, members: 18 */ /* padding: 4 */ /* forced alignments: 1 */ /* last cacheline: 40 bytes */ } __attribute__((__aligned__(8))); If a future kernel extension adds a new 4-byte field, older userspace programs allocating this structure on the stack might inadvertently pass uninitialized stack garbage into the new field, permanently breaking backward compatibility. -- sashiko [1] Fix it by changing sizeof(info) to offsetofend(struct bpf_map_info, hash_size). And, add "__u32 :32" to the tail of struct bpf_map_info. [1] https://lore.kernel.org/bpf/20260513224823.6494FC19425@smtp.kernel.org/ Fixes: ea2e6467ac36 ("bpf: Return hashes of maps in BPF_OBJ_GET_INFO_BY_FD") Acked-by: Mykyta Yatsenko Signed-off-by: Leon Hwang --- include/uapi/linux/bpf.h | 1 + kernel/bpf/syscall.c | 5 +++-- tools/include/uapi/linux/bpf.h | 1 + 3 files changed, 5 insertions(+), 2 deletions(-) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index bed9b1b4d5ef..e1730f449d9e 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -6733,6 +6733,7 @@ struct bpf_map_info { __u64 map_extra; __aligned_u64 hash; __u32 hash_size; + __u32 :32; } __attribute__((aligned(8))); struct bpf_btf_info { diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 31a3b70a0b5d..89f020a44fc9 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -5406,10 +5406,11 @@ static int bpf_map_get_info_by_fd(struct file *file, { struct bpf_map_info __user *uinfo = u64_to_user_ptr(attr->info.info); struct bpf_map_info info; - u32 info_len = attr->info.info_len; + u32 info_len = attr->info.info_len, len; int err; - err = bpf_check_uarg_tail_zero(USER_BPFPTR(uinfo), sizeof(info), info_len); + len = offsetofend(struct bpf_map_info, hash_size); + err = bpf_check_uarg_tail_zero(USER_BPFPTR(uinfo), len, info_len); if (err) return err; info_len = min_t(u32, sizeof(info), info_len); diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index 7d0b282ba674..7caf667e86fe 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -6733,6 +6733,7 @@ struct bpf_map_info { __u64 map_extra; __aligned_u64 hash; __u32 hash_size; + __u32 :32; } __attribute__((aligned(8))); struct bpf_btf_info { -- 2.54.0