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 8A22020F88 for ; Fri, 21 Jul 2023 18:54:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A6BAEC433C9; Fri, 21 Jul 2023 18:54:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1689965670; bh=una6Je6luT+7lgXj5ss00MzUO9SOy1hhZmt9SkhbR3o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=yK1P1Or9yNGnwlmq8w9C3hpJicr5M4t2paZdYY/eBwMB+Yi6fUgHmBZl1aFLcXTi4 E7AsgP97e918T7DZrVDWTjT0LFinbrDmNgQamGNz9FdOEaVbz52OGXreF2HauwRU+b UUZmRPGARp+85vHLLJHDhm8OdpqvTpZjrMrq78pY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Martin KaFai Lau , Stanislav Fomichev , Sasha Levin Subject: [PATCH 5.15 044/532] bpf: Dont EFAULT for {g,s}setsockopt with wrong optlen Date: Fri, 21 Jul 2023 17:59:08 +0200 Message-ID: <20230721160617.035993292@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230721160614.695323302@linuxfoundation.org> References: <20230721160614.695323302@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Stanislav Fomichev [ Upstream commit 29ebbba7d46136cba324264e513a1e964ca16c0a ] With the way the hooks implemented right now, we have a special condition: optval larger than PAGE_SIZE will expose only first 4k into BPF; any modifications to the optval are ignored. If the BPF program doesn't handle this condition by resetting optlen to 0, the userspace will get EFAULT. The intention of the EFAULT was to make it apparent to the developers that the program is doing something wrong. However, this inadvertently might affect production workloads with the BPF programs that are not too careful (i.e., returning EFAULT for perfectly valid setsockopt/getsockopt calls). Let's try to minimize the chance of BPF program screwing up userspace by ignoring the output of those BPF programs (instead of returning EFAULT to the userspace). pr_info_once those cases to the dmesg to help with figuring out what's going wrong. Fixes: 0d01da6afc54 ("bpf: implement getsockopt and setsockopt hooks") Suggested-by: Martin KaFai Lau Signed-off-by: Stanislav Fomichev Link: https://lore.kernel.org/r/20230511170456.1759459-2-sdf@google.com Signed-off-by: Martin KaFai Lau Signed-off-by: Sasha Levin --- kernel/bpf/cgroup.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c index 87174832aa86d..297569e5c6399 100644 --- a/kernel/bpf/cgroup.c +++ b/kernel/bpf/cgroup.c @@ -1481,6 +1481,12 @@ int __cgroup_bpf_run_filter_setsockopt(struct sock *sk, int *level, ret = 1; } else if (ctx.optlen > max_optlen || ctx.optlen < -1) { /* optlen is out of bounds */ + if (*optlen > PAGE_SIZE && ctx.optlen >= 0) { + pr_info_once("bpf setsockopt: ignoring program buffer with optlen=%d (max_optlen=%d)\n", + ctx.optlen, max_optlen); + ret = 0; + goto out; + } ret = -EFAULT; } else { /* optlen within bounds, run kernel handler */ @@ -1536,6 +1542,7 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level, .optname = optname, .retval = retval, }; + int orig_optlen; int ret; /* Opportunistic check to see whether we have any BPF program @@ -1545,6 +1552,7 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level, if (__cgroup_bpf_prog_array_is_empty(cgrp, CGROUP_GETSOCKOPT)) return retval; + orig_optlen = max_optlen; ctx.optlen = max_optlen; max_optlen = sockopt_alloc_buf(&ctx, max_optlen, &buf); @@ -1568,6 +1576,7 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level, ret = -EFAULT; goto out; } + orig_optlen = ctx.optlen; if (copy_from_user(ctx.optval, optval, min(ctx.optlen, max_optlen)) != 0) { @@ -1587,6 +1596,12 @@ int __cgroup_bpf_run_filter_getsockopt(struct sock *sk, int level, } if (optval && (ctx.optlen > max_optlen || ctx.optlen < 0)) { + if (orig_optlen > PAGE_SIZE && ctx.optlen >= 0) { + pr_info_once("bpf getsockopt: ignoring program buffer with optlen=%d (max_optlen=%d)\n", + ctx.optlen, max_optlen); + ret = retval; + goto out; + } ret = -EFAULT; goto out; } -- 2.39.2