From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 EBAEB346772 for ; Sat, 28 Feb 2026 18:07:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772302073; cv=none; b=WLqAGnYIu9zhjNVGeRriD+TVMBGVHbMpNTb8Q8hODUz7vv3gu8D0stPwMGvhoJWymzMHxhaNwx0KmolbVYcO+4VV/fvApw5xgjVIqZ8Zip0REVo0utOFse3rCDSNlVo2Si9oVIQPGkr6WBd1y/FtEVtJN/PvV90md1QmVjn31Vc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772302073; c=relaxed/simple; bh=hKFKnw75Y62EXR5ctrFzNlwXeqp9gkGDG3II9K9ybfY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BtcCz869kAofhv3sYL38D+BOjoAinDw+C44jW8Bq6ELAqAUlDxmDW4m4Vi5OCu76SfD9SkQArOLp/8e1CdCVtMa5WkoKpRe8ELtr+aF+2Mtc0nPtt/OMpA9PoYY/Jo0/2PUWtRTLNqZp0ECBEqSE5sRbqLknn6wg9OFT9QBkLzE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=CPRGKeCL; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="CPRGKeCL" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1680FC19423; Sat, 28 Feb 2026 18:07:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772302072; bh=hKFKnw75Y62EXR5ctrFzNlwXeqp9gkGDG3II9K9ybfY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CPRGKeCLaBEz4PB1TvfMyP+fFMFNb1uvEKlcG4+YhBP9O3WPE+kQbM0R+NRWZH+Bl AZRC2x9QtAHAOHmx4ZFRlZWG8NYlCuXEl1RQZ5l5im4zj3aHruip3Ub5f5yVpcXJhN 9E7sW8oAv/vUqS+9lZU+70W1Qb5INODeJXiAzx+IYkoyYHUuYU9p9Thbmpudo85Ucw JCLgmfFGpAStKxwNG0fm2wpYhUsMS9Smviw962Z5grUzyid0jfXORwCtlW2oFPEGBN QtCCfFrYAKw1eqLdsKWS6wzBqJtuC41rVh9sfMOddWRFhfVxlSBvAWtmH8bYojRgSb LKmxpE6Zi3k2A== From: Sasha Levin To: patches@lists.linux.dev Cc: Paul Chaignon , Alexei Starovoitov , Sasha Levin Subject: [PATCH 6.6 052/283] bpf: Fix bpf_xdp_store_bytes proto for read-only arg Date: Sat, 28 Feb 2026 13:03:14 -0500 Message-ID: <20260228180709.1583486-52-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260228180709.1583486-1-sashal@kernel.org> References: <20260228180709.1583486-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit From: Paul Chaignon [ Upstream commit 6557f1565d779851c4db9c488c49c05a47a6e72f ] While making some maps in Cilium read-only from the BPF side, we noticed that the bpf_xdp_store_bytes proto is incorrect. In particular, the verifier was throwing the following error: ; ret = ctx_store_bytes(ctx, l3_off + offsetof(struct iphdr, saddr), &nat->address, 4, 0); 635: (79) r1 = *(u64 *)(r10 -144) ; R1=ctx() R10=fp0 fp-144=ctx() 636: (b4) w2 = 26 ; R2=26 637: (b4) w4 = 4 ; R4=4 638: (b4) w5 = 0 ; R5=0 639: (85) call bpf_xdp_store_bytes#190 write into map forbidden, value_size=6 off=0 size=4 nat comes from a BPF_F_RDONLY_PROG map, so R3 is a PTR_TO_MAP_VALUE. The verifier checks the helper's memory access to R3 in check_mem_size_reg, as it reaches ARG_CONST_SIZE argument. The third argument has expected type ARG_PTR_TO_UNINIT_MEM, which includes the MEM_WRITE flag. The verifier thus checks for a BPF_WRITE access on R3. Given R3 points to a read-only map, the check fails. Conversely, ARG_PTR_TO_UNINIT_MEM can also lead to the helper reading from uninitialized memory. This patch simply fixes the expected argument type to match that of bpf_skb_store_bytes. Fixes: 3f364222d032 ("net: xdp: introduce bpf_xdp_pointer utility routine") Signed-off-by: Paul Chaignon Link: https://lore.kernel.org/r/9fa3c9f72d806e82541071c4df88b8cba28ad6a9.1769875479.git.paul.chaignon@gmail.com Signed-off-by: Alexei Starovoitov Signed-off-by: Sasha Levin --- net/core/filter.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/core/filter.c b/net/core/filter.c index ddb6d3dd34deb..e5dc1f699297b 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -4118,7 +4118,7 @@ static const struct bpf_func_proto bpf_xdp_store_bytes_proto = { .ret_type = RET_INTEGER, .arg1_type = ARG_PTR_TO_CTX, .arg2_type = ARG_ANYTHING, - .arg3_type = ARG_PTR_TO_UNINIT_MEM, + .arg3_type = ARG_PTR_TO_MEM | MEM_RDONLY, .arg4_type = ARG_CONST_SIZE, }; -- 2.51.0