Re: [PATCH] inotify: hide internal kernel bits from fdinfo

[Andrey Wagin]

2015-09-21 21:45 GMT+03:00 Dave Hansen <dave@xxxxxxxx>:
>
> From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
>
> There was a report that my patch:
>
>         inotify: actually check for invalid bits in sys_inotify_add_watch()
>
> broke CRIU.
>
> The reason is that CRIU looks up raw flags in /proc/$pid/fdinfo/*
> to figure out how to rebuild inotify watches and then passes those
> flags directly back in to the inotify API.  One of those flags
> (FS_EVENT_ON_CHILD) is set in mark->mask, but is not part of the
> inotify API.  It is used inside the kernel to _implement_ inotify
> but it is not and has never been part of the API.
>
> My patch above ensured that we only allow bits which are part of
> the API (IN_ALL_EVENTS).  This broke CRIU.
>
> FS_EVENT_ON_CHILD is really internal to the kernel.  It is set
> _anyway_ on all inotify marks.  So, CRIU was really just trying
> to set a bit that was already set.
>
> This patch hides that bit from fdinfo.  CRIU will not see the
> bit, not try to set it, and should work as before.  We should not
> have been exposing this bit in the first place, so this is a good
> patch independent of the CRIU problem.
>
> Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> Reported-by: Andrey Wagin <avagin@xxxxxxxxx>

Acked-by: Andrey Vagin <avagin@xxxxxxxxxx>

Thanks,
Andrey

> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
> Cc: xemul@xxxxxxxxxxxxx
> Cc: Eric Paris <eparis@xxxxxxxxxx>
> Cc: john@xxxxxxxxxxxxxxxxx
> Cc: rlove@xxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> ---
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