From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-183.mta1.migadu.com (out-183.mta1.migadu.com [95.215.58.183]) (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 47B34480DC0 for ; Wed, 3 Jun 2026 14:45:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.183 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780497953; cv=none; b=fQwprHszXP58fdWjWf4u8NJ/ogqEmePdZE57wvax0cQelD2GyCqBXYdetdEVvCuz4LbZTgp+LOcBwBilgBJyrYsbrjBD93nAmex5iYuxSQ+0T6EU6JEeAT4VCpR9P3d+jJrr3J/PS4VtewtNwSG6bJqVAepag/38MvTJ0k02IKw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780497953; c=relaxed/simple; bh=qrblDqB4/8UTNvwsfuUvtB8MQ8mzMY7zUiDc+Mbzycs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=eejECBJMR8h6ibBoJqlyfnJk/Ksn2V2Fb2Z5epY9WTiVWg1GlSzkMfMPRoBFgFe8Vw/gxAYz/2OijNb3W/ndWgCMLUzNEFvftjYofT7YzRC2bw/WzQT2CMlyJXgBG2RIsZFiutk1a+N/+eKtH29Qiwhe2AOtFqRraVvAqSCFY0A= 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=MQqEf4xo; arc=none smtp.client-ip=95.215.58.183 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="MQqEf4xo" 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=1780497949; 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=I8qiNtbqWgHQYGAUM0S9VH2blx8YU6TzskWNL0hFkek=; b=MQqEf4xoFIcpXEy97BWN13L2YnJq7b8UasO2tv25zetxF3l6LgsOWuKg4Gdxk81+1BNx9G DQNdhbZTe7nxBDJG6xZXtZZ17mmAHdA8yaAMFsHR0rKUuYOAinvrhvrgSy+QMq9jKuPIW6 jSgcqZC+f0TjB3mHeqY8UiAe0sIfBYc= 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 , Stanislav Fomichev , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, kernel-patches-bot@fb.com Subject: [PATCH bpf-next 1/3] bpf: Check tail zero of bpf_map_info Date: Wed, 3 Jun 2026 22:45:16 +0800 Message-ID: <20260603144518.67065-2-leon.hwang@linux.dev> In-Reply-To: <20260603144518.67065-1-leon.hwang@linux.dev> References: <20260603144518.67065-1-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). [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") Signed-off-by: Leon Hwang --- kernel/bpf/syscall.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 625a4366fe6d..1007fb7c87e9 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -5400,10 +5400,11 @@ 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); -- 2.54.0