ACK: [B][C][SRU][PATCH v2 0/2] Handle overflow for file-max

[Colin Ian King]

On 28/06/2019 09:24, Po-Hsu Lin wrote:
> V2: description change in the cover-letter
> 
> == SRU Justification ==
> Currently, when writing 2^64-1 or 2^63 into file-max:
>    echo 18446744073709551616 > /proc/sys/fs/file-max
> 
> Will make the system stuck with "Too many open files in system" error within seconds.
> 
> The upper and lower limit need to be defined properly to avoid this.
> (The case for passing 2^64 will be addressed in bug 1833935)
> 
> This failure was reported by the case 2 and 3 of the sysctl02 test in LTP:
> sysctl02 2 TFAIL: /proc/sys/fs/file-max overflows and set to 18446744073709551615
> sysctl02 3 TFAIL: /proc/sys/fs/file-max overflows and set to 9223372036854775808
> 
> == Fix ==
> * 32a5ad9c sysctl: handle overflow for file-max
> * 9002b214 kernel/sysctl.c: fix out-of-bounds access when setting file-max
> 
> These patches can be cherry-picked into B/C.
> They have already been applied in X/D from stable update process.
> 
> == Test ==
> Test kernel could be found here:
> https://people.canonical.com/~phlin/kernel/lp-1834310-file-max/
> 
> Tested OK on KVM nodes with the following command (extracted from the
> sysctl02 test case in LTP):
>   $ cat /proc/sys/fs/file-max
>   $ sudo sysctl -w -q fs.file-max=18446744073709551615
>   $ cat /proc/sys/fs/file-max
>   $ sudo sysctl -w -q fs.file-max=9223372036854775808
>   $ cat /proc/sys/fs/file-max
> 
> All three file-max output should be identical with the patched kernel.
> 
> This is because the file-max value is parsed via
> __do_proc_doulongvec_minmax(), which does not report error when min or
> max are exceeded but it will just keep the old value instead.
> 
> == Regression Potential ==
> Low, just adding boundaries to the file-max.
> And it's been applied in some of our kernels for a while.
> 
> Christian Brauner (1):
>   sysctl: handle overflow for file-max
> 
> Will Deacon (1):
>   kernel/sysctl.c: fix out-of-bounds access when setting file-max
> 
>  kernel/sysctl.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 

Looks good to me.

Acked-by: Colin Ian King <colin.king at canonical.com>