NAK[Unstable]: [X][B][C][D][Unstable][SRU][PATCH 0/1] sysctl: handle overflow in proc_get_long

[Seth Forshee]

On Fri, Jun 28, 2019 at 03:42:27PM +0800, Po-Hsu Lin wrote:
> == SRU Justification ==
> With the upper / lower boundary confined in bug 1834310, the file-max
> is still suffering with overflow issue.
> 
> This is because the simple_strtoul() used in proc_get_long() to parse
> user input explicitly ignores overflows. So when you tried to put 2^64
> into file-max, it will:
>     # echo 18446744073709551616 > /proc/sys/fs/file-max
>     # cat /proc/sys/fs/file-max
>     0
> 
> Which will cause your system to silently die behind your back.
> 
> This issue was reported by the case 1 of the sysctl02 test in LTP:
> sysctl02 1 TFAIL: /proc/sys/fs/file-max overflows and set to 0
> 
> 
> == Fix ==
> * 7f2923c4 (sysctl: handle overflow in proc_get_long)
> 
> A new strtoul_lenient() was introduced here to solve this issue, with
> extra check to notify userspace with -EINVAL.
> 
> This patch can be cherry-picked into B/C/D/E, it needs some content
> adjustment for X.
> 
> == Test ==
> Test kernels could be found here:
> https://people.canonical.com/~phlin/kernel/lp-1833935-proc_get_long/
> 
> The attempt to set file-max to 2^64 will be rejected:
> $ sudo sysctl -w -q fs.file-max=18446744073709551616
> sysctl: setting key "fs.file-max": Invalid argument
> 
> Tested and passed with these kernels on AMD64 KVM nodes.
> 
> == Regression Potential ==
> Low, the newly introduced function strtoul_lenient() is just for
> proc_get_long here.

Patch is from 5.2-rc1, so unstable already has it.