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 EDC703845B3; Sat, 17 Oct 2026 16:13:42 +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=1792253627; cv=none; b=WJmp9stPf7ShyZp76nt8JeCR6KsYuSjCfemOVZIRNbX63WOZ06UYmxpC99F2XgTsCF0s/Ost/GF3uC5hK160w1KGCDPbTi46t99tvUgj7cUgniX7lXqPcQMMHdWpyStrdVPgbbaehuqm39o0K2ZANcY54LB/fGnjan0jo4RIyIw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792253627; c=relaxed/simple; bh=2WNSrTlz0n0R0uYpcB7DYKwKyGYqD7Xo7eG8g3rAj/A=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ZRi+U3hIFwyt94hi7jGjHzn6/nE4hn2iB/zSMpjbizYkSx2sZo5Uv7UMKv5OIpLOhyC4gbFyO2Z3IHSrOkFokaySXkXFwomb+tn8qmcJdv+or5/nnT4pZWH6nvlb4VQgxYEn2yhmS3XpQyK2+dxKC1eSm3A/aTLQe9JboZtsy7Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=2eA+i9iv; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="2eA+i9iv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2379A1F000C6; Sat, 17 Oct 2026 16:13:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1792253622; bh=AqrSPh9g+yXWTCO/7PNQzspQQdVVLW5jj82U3YHw5XQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=2eA+i9ivnDTCu6GOxS82d5NcmJQvQ3Isl1HCW1Si4zbIcLXUFxsvlOtLKPK7r85IA hdol8xW+OaFBdo1IKyZgQC9Q6nJiZo8y3RtoVaVKMVl6S/CzetptmevMwdaCiadljE Q5kVKJcLuxUSn1Ud/A8oUGyLt+CSWFpluqB0NXrE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Gustavo A. R. Silva" , "Michael S. Tsirkin" , Paolo Abeni , Sasha Levin Subject: [PATCH 6.12 179/869] virtio_net: Fix misalignment bug in struct virtnet_info Date: Sat, 17 Oct 2026 17:50:20 +0200 Message-ID: <20261017160041.641833855@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261017160036.979869304@linuxfoundation.org> References: <20261017160036.979869304@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Gustavo A. R. Silva [ Upstream commit 4156c3745f06bc197094b9ee97a9584e69ed00bf ] Use the new TRAILING_OVERLAP() helper to fix a misalignment bug along with the following warning: drivers/net/virtio_net.c:429:46: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] This helper creates a union between a flexible-array member (FAM) and a set of members that would otherwise follow it (in this case `u8 rss_hash_key_data[VIRTIO_NET_RSS_MAX_KEY_SIZE];`). This overlays the trailing members (rss_hash_key_data) onto the FAM (hash_key_data) while keeping the FAM and the start of MEMBERS aligned. The static_assert() ensures this alignment remains. Notice that due to tail padding in flexible `struct virtio_net_rss_config_trailer`, `rss_trailer.hash_key_data` (at offset 83 in struct virtnet_info) and `rss_hash_key_data` (at offset 84 in struct virtnet_info) are misaligned by one byte. See below: struct virtio_net_rss_config_trailer { __le16 max_tx_vq; /* 0 2 */ __u8 hash_key_length; /* 2 1 */ __u8 hash_key_data[]; /* 3 0 */ /* size: 4, cachelines: 1, members: 3 */ /* padding: 1 */ /* last cacheline: 4 bytes */ }; struct virtnet_info { ... struct virtio_net_rss_config_trailer rss_trailer; /* 80 4 */ /* XXX last struct has 1 byte of padding */ u8 rss_hash_key_data[40]; /* 84 40 */ ... /* size: 832, cachelines: 13, members: 48 */ /* sum members: 801, holes: 8, sum holes: 31 */ /* paddings: 2, sum paddings: 5 */ }; After changes, those members are correctly aligned at offset 795: struct virtnet_info { ... union { struct virtio_net_rss_config_trailer rss_trailer; /* 792 4 */ struct { unsigned char __offset_to_hash_key_data[3]; /* 792 3 */ u8 rss_hash_key_data[40]; /* 795 40 */ }; /* 792 43 */ }; /* 792 44 */ ... /* size: 840, cachelines: 14, members: 47 */ /* sum members: 801, holes: 8, sum holes: 35 */ /* padding: 4 */ /* paddings: 1, sum paddings: 4 */ /* last cacheline: 8 bytes */ }; As a result, the RSS key passed to the device is shifted by 1 byte: the last byte is cut off, and instead a (possibly uninitialized) byte is added at the beginning. As a last note `struct virtio_net_rss_config_hdr *rss_hdr;` is also moved to the end, since it seems those three members should stick around together. :) Cc: stable@vger.kernel.org Fixes: ed3100e90d0d ("virtio_net: Use new RSS config structs") Signed-off-by: Gustavo A. R. Silva Acked-by: Michael S. Tsirkin Link: https://patch.msgid.link/aWIItWq5dV9XTTCJ@kspp Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin --- drivers/net/virtio_net.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index cb640d29d7912..851defa105e04 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -409,9 +409,6 @@ struct virtnet_info { u16 rss_indir_table_size; u32 rss_hash_types_supported; u32 rss_hash_types_saved; - struct virtio_net_rss_config_hdr *rss_hdr; - struct virtio_net_rss_config_trailer rss_trailer; - u8 rss_hash_key_data[VIRTIO_NET_RSS_MAX_KEY_SIZE]; /* Has control virtqueue */ bool has_cvq; @@ -470,7 +467,16 @@ struct virtnet_info { struct failover *failover; u64 device_stats_cap; + + struct virtio_net_rss_config_hdr *rss_hdr; + + /* Must be last as it ends in a flexible-array member. */ + TRAILING_OVERLAP(struct virtio_net_rss_config_trailer, rss_trailer, hash_key_data, + u8 rss_hash_key_data[VIRTIO_NET_RSS_MAX_KEY_SIZE]; + ); }; +static_assert(offsetof(struct virtnet_info, rss_trailer.hash_key_data) == + offsetof(struct virtnet_info, rss_hash_key_data)); struct padded_vnet_hdr { struct virtio_net_hdr_v1_hash hdr; -- 2.53.0