lkml.org 
[lkml]   [2019]   [Apr]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH 4.4 014/168] sysctl: handle overflow for file-max
On Wed, Apr 24, 2019 at 7:16 PM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
>
> [ Upstream commit 32a5ad9c22852e6bd9e74bdec5934ef9d1480bc5 ]
>
> Currently, when writing
>
> echo 18446744073709551616 > /proc/sys/fs/file-max
>
> /proc/sys/fs/file-max will overflow and be set to 0. That quickly
> crashes the system.
>
> This commit sets the max and min value for file-max. The max value is
> set to long int. Any higher value cannot currently be used as the
> percpu counters are long ints and not unsigned integers.
>
> Note that the file-max value is ultimately parsed via
> __do_proc_doulongvec_minmax(). This function does not report error when
> min or max are exceeded. Which means if a value largen that long int is
> written userspace will not receive an error instead the old value will be
> kept. There is an argument to be made that this should be changed and
> __do_proc_doulongvec_minmax() should return an error when a dedicated min
> or max value are exceeded. However this has the potential to break
> userspace so let's defer this to an RFC patch.
>
> Link: http://lkml.kernel.org/r/20190107222700.15954-3-christian@brauner.io
> Signed-off-by: Christian Brauner <christian@brauner.io>
> Acked-by: Kees Cook <keescook@chromium.org>
> Cc: Alexey Dobriyan <adobriyan@gmail.com>
> Cc: Al Viro <viro@zeniv.linux.org.uk>
> Cc: Dominik Brodowski <linux@dominikbrodowski.net>
> Cc: "Eric W. Biederman" <ebiederm@xmission.com>
> Cc: Joe Lawrence <joe.lawrence@redhat.com>
> Cc: Luis Chamberlain <mcgrof@kernel.org>
> Cc: Waiman Long <longman@redhat.com>
> [christian@brauner.io: v4]
> Link: http://lkml.kernel.org/r/20190210203943.8227-3-christian@brauner.io
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Sasha Levin <sashal@kernel.org>

Hey Greg,

Just an heads-up. This patch triggered a KASAN warning and Will has
sent a fix for that
which is already in master.
So if you backport this patch you likely also want to backport

9002b21465fa4d829edfc94a5a441005cffaa972

(See https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9002b21465fa4d829edfc94a5a441005cffaa972
)

Seems we missed a Cc: for stable in there. Sorry about that.
Thanks!
Christian

> ---
> kernel/sysctl.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index beadcf83ceba..2f98b11477b8 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -126,6 +126,7 @@ static int __maybe_unused one = 1;
> static int __maybe_unused two = 2;
> static int __maybe_unused four = 4;
> static unsigned long one_ul = 1;
> +static unsigned long long_max = LONG_MAX;
> static int one_hundred = 100;
> #ifdef CONFIG_PRINTK
> static int ten_thousand = 10000;
> @@ -1603,6 +1604,8 @@ static struct ctl_table fs_table[] = {
> .maxlen = sizeof(files_stat.max_files),
> .mode = 0644,
> .proc_handler = proc_doulongvec_minmax,
> + .extra1 = &zero,
> + .extra2 = &long_max,
> },
> {
> .procname = "nr_open",
> --
> 2.19.1
>
>
>

\
 
 \ /
  Last update: 2019-04-24 23:51    [W:0.554 / U:5.204 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site