[Devel] [PATCH] fs/proc/base.c: fix GPF in /proc/$PID/map_files

[Cyrill Gorcunov]

On Fri, Jul 14, 2017 at 08:25:35PM +0400, Stanislav Kinsburskiy wrote:
> From: Artem Fetishev <artem_fetishev at epam.com>
> 
> The expected logic of proc_map_files_get_link() is either to return 0
> and initialize 'path' or return an error and leave 'path' uninitialized.
> 
> By the time dname_to_vma_addr() returns 0 the corresponding vma may have
> already be gone.  In this case the path is not initialized but the
> return value is still 0.  This results in 'general protection fault'
> inside d_path().
> 
> Steps to reproduce:
> 
>   CONFIG_CHECKPOINT_RESTORE=y
> 
>     fd = open(...);
>     while (1) {
>         mmap(fd, ...);
>         munmap(fd, ...);
>     }
> 
>   ls -la /proc/$PID/map_files
> 
> Addresses https://bugzilla.kernel.org/show_bug.cgi?id=68991
> 
> https://jira.sw.ru/browse/PSBM-68472
> 
> Signed-off-by: Artem Fetishev <artem_fetishev at epam.com>
> Signed-off-by: Aleksandr Terekhov <aleksandr_terekhov at epam.com>
> Reported-by: <wiebittewas at gmail.com>
> Acked-by: Pavel Emelyanov <xemul at parallels.com>
> Acked-by: Cyrill Gorcunov <gorcunov at openvz.org>
> Reviewed-by: "Eric W. Biederman" <ebiederm at xmission.com>
> Cc: <stable at vger.kernel.org>
> Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
> Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
> Signed-off-by: Stanislav Kinsburskiy <skinsbursky at virtuozzo.com>
Acked-by: Cyrill Gorcunov <gorcunov at openvz.org>