Re: [PATCH] user_ns: use correct check for single-threadedness

[Rik van Riel]

On 07/28/2015 01:15 PM, Kees Cook wrote:
> From: Ricky Zhou <rickyz@xxxxxxxxxxxx>
> 
> Checking mm_users > 1 does not mean a process is multithreaded. For
> example, reading /proc/PID/maps temporarily increments mm_users, allowing
> other processes to (accidentally) interfere with unshare() calls.
> 
> This fixes observed failures of unshare(CLONE_NEWUSER) incorrectly
> returning EINVAL if another processes happened to be simultaneously
> reading the maps file.
> 
> Signed-off-by: Ricky Zhou <rickyz@xxxxxxxxxxxx>
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx

Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>

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