From nobody Sat Nov 23 18:02:09 2024 Received: from relay2-d.mail.gandi.net (relay2-d.mail.gandi.net [217.70.183.194]) (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 69A381DFF7; Tue, 12 Nov 2024 13:16:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.70.183.194 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731417363; cv=none; b=cww9JO9SaTdCD8dAiilvxecLVb+Mm0qNcSpel/yHmInAl4bag0aOG0us4MqmRZtWqwZdODj0Q8XeOff1lCQwXi4+Z5eFkjsmpHEFzKylpiaRvEwGVItFC1zNQCcaZ8XXdIguSGHsJGD9cWDttH+bLTc1emuHzIXvM3X4JAXhoQw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731417363; c=relaxed/simple; bh=qfOxXZl3i+Y1oYo8sGRDtKZMnRF7XlS1req/aH6k6aU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=sjVwdPXCqdcSFxSc9w/cVv/Jf7yQpxwBi9ShS5ztfXZyataZh/t4JX8dbXZO67VAF+Wi78JcNC83QwJdFqOYOPSWaUofEwomISVHTbFClsbAmturTYMrYoY6bhhlWy6IVeUYnHDir+YazUGxLA4IjMnnQA0axJqKvpz76iC4Vd8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=clip-os.org; spf=pass smtp.mailfrom=clip-os.org; dkim=pass (2048-bit key) header.d=clip-os.org header.i=@clip-os.org header.b=aUKmRdWq; arc=none smtp.client-ip=217.70.183.194 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=clip-os.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=clip-os.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=clip-os.org header.i=@clip-os.org header.b="aUKmRdWq" Received: by mail.gandi.net (Postfix) with ESMTPSA id 1274540009; Tue, 12 Nov 2024 13:15:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=clip-os.org; s=gm1; t=1731417358; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=q32Mu1dm6Jq7pbi1U+EvpEksk9Tb+6KgFIz94SMpnwA=; b=aUKmRdWq8Mi5vXx2PojitY93MZJ+cElBXrTD0ft9KyK9YACwU/IDVOWZv9ah9uv569g3su l1NVQw1nO9HwagKTJuAyBsWzoaK/FhjbDvt7fY9gdaYSlhHLcqtrPG0l4lWRk5teTPKBv2 IGXWbuSmYd9Mexk1hdAaz4DTytFF0kKMLjZ1Qi5JjfamTcuHcFkwYZ5PqZNudtZ1zTKLBl HMxjIqwFiuPnflFvVVzbdFuIZVsXyQzz7M5ClcuQ6dl4/T5qqix4+kCuntWzo1mE803dy1 SlzOugn5G5D//KxHZg0M7eXPkixQeXSSLC6WiSw874IqRyORA5CZherxmcN0Kg== From: nicolas.bouchinet@clip-os.org To: linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, linux-fsdevel@vger.kernel.org Cc: nicolas.bouchinet@clip-os.org, Nicolas Bouchinet , Greg Kroah-Hartman , Jiri Slaby , Alexander Viro , Christian Brauner , Jan Kara , Luis Chamberlain , Kees Cook , Joel Granados , Andrew Morton , Neil Horman , Lin Feng , "Theodore Ts'o" Subject: [PATCH 1/3] coredump: Fixes core_pipe_limit sysctl proc_handler Date: Tue, 12 Nov 2024 14:13:29 +0100 Message-ID: <20241112131357.49582-2-nicolas.bouchinet@clip-os.org> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20241112131357.49582-1-nicolas.bouchinet@clip-os.org> References: <20241112131357.49582-1-nicolas.bouchinet@clip-os.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-GND-Sasl: nicolas.bouchinet@clip-os.org Content-Type: text/plain; charset="utf-8" From: Nicolas Bouchinet proc_dointvec converts a string to a vector of signed int, which is stored in the unsigned int .data core_pipe_limit. It was thus authorized to write a negative value to core_pipe_limit sysctl which once stored in core_pipe_limit, leads to the signed int dump_count check against core_pipe_limit never be true. The same can be achieved with core_pipe_limit set to INT_MAX. Any negative write or >=3D to INT_MAX in core_pipe_limit sysctl would hypothetically allow a user to create very high load on the system by running processes that produces a coredump in case the core_pattern sysctl is configured to pipe core files to user space helper. Memory or PID exhaustion should happen before but it anyway breaks the core_pipe_limit semantic This commit fixes this by changing core_pipe_limit sysctl's proc_handler to proc_dointvec_minmax and bound checking between SYSCTL_ZERO and SYSCTL_INT_MAX. Fixes: a293980c2e26 ("exec: let do_coredump() limit the number of concurren= t dumps to pipes") Signed-off-by: Nicolas Bouchinet Reviewed-by: Lin Feng --- fs/coredump.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/fs/coredump.c b/fs/coredump.c index 7f12ff6ad1d3e..8ea5896e518dd 100644 --- a/fs/coredump.c +++ b/fs/coredump.c @@ -616,7 +616,8 @@ void do_coredump(const kernel_siginfo_t *siginfo) cprm.limit =3D RLIM_INFINITY; =20 dump_count =3D atomic_inc_return(&core_dump_count); - if (core_pipe_limit && (core_pipe_limit < dump_count)) { + if ((core_pipe_limit && (core_pipe_limit < dump_count)) || + (core_pipe_limit && dump_count =3D=3D INT_MAX)) { printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n", task_tgid_vnr(current), current->comm); printk(KERN_WARNING "Skipping core dump\n"); @@ -1024,7 +1025,9 @@ static struct ctl_table coredump_sysctls[] =3D { .data =3D &core_pipe_limit, .maxlen =3D sizeof(unsigned int), .mode =3D 0644, - .proc_handler =3D proc_dointvec, + .proc_handler =3D proc_dointvec_minmax, + .extra1 =3D SYSCTL_ZERO, + .extra2 =3D SYSCTL_INT_MAX, }, { .procname =3D "core_file_note_size_limit", --=20 2.47.0