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 9A9555221CB; Wed, 30 Sep 2026 17:29:51 +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=1790789393; cv=none; b=GT5D7njS22W4OLxeN5GuEywvc+qFcLQEp2COXj0wFFAK2G/21v0VifTAAhFAKcRxacgJCx+JsTh/06sirFop0mxYWRSZH5W17mfaiHomq7C9mR2G43Mlk9qqQat7NR6acTuVwEIakdcq/e9R9MWA3sH94iGkJ4IFdakbMqySWjQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790789393; c=relaxed/simple; bh=cTTNIEVvOadLiV7lz6Ok7pylNn4Lovp8Z7MaJ42LQgY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=BufbsGN/wFNf6A72z7zHYuVYjdh3OoA3Q5sKO12zivVmj33aTrHJ+FVCGQ1YyF8g9jM3vaVHwJnGjqhA3oBfBEnyysX8cWpcTV2OxDardhvWFpL4+7SMP0iTVknoQjGTHXT6QsJ61XSkjqp4MQ6zv4xhn+Ua0bz2bvX7LcufUTs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=RdYFKUW5; 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="RdYFKUW5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B0FF11F000FF; Wed, 30 Sep 2026 17:29:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790789391; bh=pOP4fzL8BtgEvwGZNP/WYb88tmwGbD8iYnuyTer/9jo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=RdYFKUW57+3lA75Wc65Gg8gbY4rO9/PK2+lvVQnpIz0nisGMJ2XWI7oFCPe27AoP0 uRBOLAGbfwNvlumpX2c/x8Ow8jOg5xRNVMAwluW7N1ELFhod0l30KgiVeNb4vbcIBZ ATvctPghShTzFU2tL0zhTBH/JkLM3D/SRGOvLlV0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Dairui Zhang , Willem de Bruijn , Jakub Kicinski Subject: [PATCH 6.12 462/877] af_packet: fix integer overflow in prb_calc_retire_blk_tmo() Date: Wed, 30 Sep 2026 17:22:53 +0200 Message-ID: <20260930152424.647317809@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260930152414.738996857@linuxfoundation.org> References: <20260930152414.738996857@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: Dairui Zhang commit 56d82862a0a243ac14ba11b6d7b57ddc2d064b95 upstream. prb_calc_retire_blk_tmo() computes in 32-bit int arithmetic: mbits = (blk_size_in_bytes * 8) / (1024 * 1024); If I'm reading the validation right, tp_block_size is user controlled and packet_set_ring() only rejects values that are <= 0 as int or not page aligned, so a 256MiB block goes right through (and alloc_one_pg_vec_page() even has a vzalloc fallback for it). 0x10000000 * 8 wraps to INT_MIN, and on a NIC reporting 1 Gbps (div == 1) the function ends up returning -2047. The condition is actually (8 * size) mod 2^32 >= 2^31 && div == 1, so the trigger set is [256,512), [768,1024), [1280,1536) and [1792,2048) MiB. Other sizes wrap to non-negative values and faster links divide the unsigned value back below 2^31, which is why this doesn't blow up for everyone. What makes it fatal is what happens next in init_prb_bdqc(): p1->interval_ktime = ms_to_ktime(prb_calc_retire_blk_tmo(...)); hrtimer_start(&p1->retire_blk_timer, p1->interval_ktime, HRTIMER_MODE_REL_SOFT); A negative relative timeout expires immediately. The callback unconditionally returns HRTIMER_RESTART, and hrtimer_forward() turns the negative interval into hrtimer_resolution: if (interval < hrtimer_resolution) interval = hrtimer_resolution; So the SOFT timer re-fires at the maximum rate forever, holding sk_receive_queue.lock each pass. One CPU spins in softirq until the socket is closed. Repeat with more rings and the machine is gone. The overflow itself is ancient - it was introduced together with TPACKET_V3 in f6fb8f100b80 ("af-packet: TPACKET_V3 flexible buffer implementation."). Its effect prior to f7460d2989fa ("net: af_packet: Use hrtimer to do the retire operation", v6.18) was not as clear-cut, though: the return value was stored into an unsigned short retire_blk_tov, so a negative result was truncated, and a 0-jiffy delay loop could be programmed as well. Neither is nearly as detrimental as the immediate maximum-rate spin the hrtimer conversion turned it into. (Unrelated to CVE-2019-20812 - that one was the ethtool failure path returning 0, which now returns DEFAULT_PRB_RETIRE_TOV.) Reproducer, needs CAP_NET_RAW (a --network host container has it by default) and a 1 Gbps NIC (QEMU e1000 works): int fd = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL)); bind(fd, ...); int v = TPACKET_V3; setsockopt(fd, SOL_PACKET, PACKET_VERSION, &v, sizeof(v)); struct tpacket_req3 req = { .tp_block_size = 0x10000000, .tp_block_nr = 1, .tp_frame_size = 2048, .tp_frame_nr = 0x10000000 / 2048, .tp_retire_blk_tov = 0, }; setsockopt(fd, SOL_PACKET, PACKET_RX_RING, &req, sizeof(req)); Compute in 64 bits instead. The operands are already bounded by the existing validation, so nothing else changes. If you'd prefer a different fix, just say so and I'll respin. Fixes: f6fb8f100b80 ("af-packet: TPACKET_V3 flexible buffer implementation.") Cc: stable@vger.kernel.org Signed-off-by: Dairui Zhang Reviewed-by: Willem de Bruijn Link: https://patch.msgid.link/20260923050101.1510064-1-zhangdairui@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/packet/af_packet.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -636,7 +636,7 @@ static int prb_calc_retire_blk_tmo(struc return DEFAULT_PRB_RETIRE_TOV; div = ecmd.base.speed / 1000; - mbits = (blk_size_in_bytes * 8) / (1024 * 1024); + mbits = (u64)blk_size_in_bytes * 8 / (1024 * 1024); if (div) mbits /= div;