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 A35B44F68B4; Tue, 13 Oct 2026 12:24:53 +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=1791894294; cv=none; b=jZlrMZjAjWa/kOmXOrNEnwTA4MJzIaF/J/GHXer0VJvMr0f+Pg25ygsxa7dM46xV9R1oI/42AVJb2KhMPNNvqzXY8f1vF7vESRRr1YajyJAKW5ZBsbPjiMuLCZf1E1oNUi+PON1KdGb8XqIP6OJw8x8VWHVU0H+F7IsbD8/kpdk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791894294; c=relaxed/simple; bh=vupzbVJRE6PWDWZONT2ZG2PR/qNFL7w+FODvlA8KO8Y=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=IqXpZH/2SqpPmcYlI0PgLZ+UvmQkDOEAJuAqDmwnrYeP8DVh9nE99d/ppi03xe4jOhty9EIzyGf6GwZIlDa3730Zzav4NvR/g8V8aAnWImL8vNHh77gV4QSFaRCLXWVcC/hlg6PJnXaJGT6R4gzXoVtM9AGwYnzlTWlJdDpgnQk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=SQOZ+JJC; 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="SQOZ+JJC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F26C21F00893; Tue, 13 Oct 2026 12:24:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1791894293; bh=GnWbyW1lJ/BOJf+7ANQJskg8pnKghMqJr6paa1+ndgw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=SQOZ+JJC6WkmB08LUCI6Pp/Yv885gqcG9iOGVyzQXVnzrAGA3JcR0WjOpFjd9NdlL F3wCH/svtmCW+bepev80FnVjCGWvxcebGju51JIg3B9Aet0sNQJTP0dcFVNhs87/Bl S7vLb4d6Spj92WusbHKp1jMw7iZM0dXWPogdP0JQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Nicholas Dudar , Kumar Kartikeya Dwivedi , Eduard Zingerman , Amery Hung , Sasha Levin Subject: [PATCH 6.18 485/621] bpf: Reject writes through untrusted BTF pointers Date: Tue, 13 Oct 2026 13:38:00 +0200 Message-ID: <20261013112932.341023619@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261013112920.855194808@linuxfoundation.org> References: <20261013112920.855194808@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 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Nicholas Dudar [ Upstream commit ac65c710cc643cbc52b899627577357867249530 ] check_ptr_to_btf_access() lets program-type btf_struct_access callbacks validate writes before the default BTF access path rejects non-read accesses. That bypasses the read-only policy for untrusted BTF pointers created by helpers such as bpf_rdonly_cast(). Reject non-read accesses through PTR_UNTRUSTED BTF pointers at the common entry point, before the callback branch to handle all cases. Fixes: 282de143ead9 ("bpf: Introduce allocated objects support") Signed-off-by: Nicholas Dudar Signed-off-by: Kumar Kartikeya Dwivedi Signed-off-by: Eduard Zingerman Reviewed-by: Amery Hung Signed-off-by: Eduard Zingerman Signed-off-by: Sasha Levin --- kernel/bpf/verifier.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 47549e988f2c7..696e1b8d06608 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -7372,6 +7372,11 @@ static int check_ptr_to_btf_access(struct bpf_verifier_env *env, return -EACCES; } + if (atype != BPF_READ && (type_flag(reg->type) & PTR_UNTRUSTED)) { + verbose(env, "only read is supported\n"); + return -EACCES; + } + if (env->ops->btf_struct_access && !type_is_alloc(reg->type) && atype == BPF_WRITE) { if (!btf_is_kernel(reg->btf)) { verifier_bug(env, "reg->btf must be kernel btf"); @@ -7380,8 +7385,7 @@ static int check_ptr_to_btf_access(struct bpf_verifier_env *env, ret = env->ops->btf_struct_access(&env->log, reg, off, size); } else { /* Writes are permitted with default btf_struct_access for - * program allocated objects (which always have ref_obj_id > 0), - * but not for untrusted PTR_TO_BTF_ID | MEM_ALLOC. + * program allocated objects (which always have ref_obj_id > 0). */ if (atype != BPF_READ && !type_is_ptr_alloc_obj(reg->type)) { verbose(env, "only read is supported\n"); -- 2.53.0