Re: [PATCH v3 0/2] sysctl: handle overflow for file-max
From: Kees Cook
Date: Mon Oct 29 2018 - 17:44:39 EST
On Mon, Oct 29, 2018 at 7:58 AM, Christian Brauner <christian@xxxxxxxxxx> wrote:
> On Wed, Oct 17, 2018 at 12:33:20AM +0200, Christian Brauner wrote:
>> Here is v3 of this patchset. Changelogs are in the individual commits.
>> 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.
>> The first version of this patch intended to detect the overflow and cap
>> at ULONG_MAX. However, we should not do this and rather return EINVAL on
>> overflow. The reasons are:
>> - this aligns with other sysctl handlers that simply reject overflows
>> (cf. , , and a bunch of others)
>> - we already do a partial fail on overflow right now
>> Namely, when the TMPBUFLEN is exceeded. So we already reject values
>> such as 184467440737095516160 (21 chars) but accept values such as
>> 18446744073709551616 (20 chars) but both are overflows. So we should
>> just always reject 64bit overflows and not special-case this based on
>> the number of chars.
>> (This patchset is in reference to https://lkml.org/lkml/2018/10/11/585.)
> Just so that we don't forget, can we make sure that this gets picked
> into linux-next? :)
I was hoping akpm would take this? Andrew, does the v3 look okay to you?