On 10/16/2018 03:53 PM, Christian Brauner wrote:
> 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 and returns -EINVAL
> when a long int is exceeded. Any higher value cannot currently be used as
> the percpu counters are long ints and not unsigned integers. This behavior
> also aligns with other tuneables that return -EINVAL when their range is
> exceeded. See e.g. [1], [2] and others.
>
> [1]: fb910c42cceb ("sysctl: check for UINT_MAX before unsigned int min/max")
> [2]: 196851bed522 ("s390/topology: correct topology mode proc handler")
>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Signed-off-by: Christian Brauner <christian@xxxxxxxxxx>
> ---
> v2->v1:
> - consistenly fail on overflow
> v0->v1:
> - if max value is < than ULONG_MAX use max as upper bound
> - (Dominik) remove double "the" from commit message
> ---
> kernel/sysctl.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 7d98e02e5d72..0874001e5435 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -127,6 +127,7 @@ 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;
> static int one_thousand = 1000;
> #ifdef CONFIG_PRINTK
> @@ -1696,6 +1697,8 @@ 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",
> @@ -2797,6 +2800,10 @@ static int __do_proc_doulongvec_minmax(void *data, struct ctl_table *table, int
> break;
> if (neg)
> continue;
> + if ((max && val > *max) || (min && val < *min)) {
> + err = -EINVAL;
> + break;
> + }
> val = convmul * val / convdiv;
Should the conversion be done before the min/max check?
> if ((min && val < *min) || (max && val > *max))
> continue;
You may be able to drop the above statement.
Cheers,
Longman
