On 15.12.2016 02:37, Eric W. Biederman wrote:
> Nikolay Borisov <n.borisov.lkml@xxxxxxxxx> writes:
>
>> This patchset converts inotify to using the newly introduced
>> per-userns sysctl infrastructure.
>>
>> Currently the inotify instances/watches are being accounted in the
>> user_struct structure. This means that in setups where multiple
>> users in unprivileged containers map to the same underlying
>> real user (i.e. pointing to the same user_struct) the inotify limits
>> are going to be shared as well, allowing one user(or application) to exhaust
>> all others limits.
>>
>> Fix this by switching the inotify sysctls to using the
>> per-namespace/per-user limits. This will allow the server admin to
>> set sensible global limits, which can further be tuned inside every
>> individual user namespace. Additionally, in order to preserve the
>> sysctl ABI make the existing inotify instances/watches sysctls
>> modify the values of the initial user namespace.
>>
>> Signed-off-by: Nikolay Borisov <n.borisov.lkml@xxxxxxxxx>
>> Acked-by: Jan Kara <jack@xxxxxxx>
>> Acked-by: Serge Hallyn <serge@xxxxxxxxxx>
>> ---
>>
>> Okay, so here is another version, which should
>> hopefully be free of slab corruptions. There was an issue
>> where in ucount.c the ifdef was checking the CONFIG_INOTIFY_USER_
>> (pay attention to the trailing _, this was clearly a mistake). This
>> led to the user_table (and all duplicated from it tables) to not
>> contain the inotify-related members. In my local testing I got
>> kasan splats even during kernel boot, due to out-of-bound writes.
>> Let's see how this version fares.
>
> So there is one more thing that needs to be addressed with your patch.
>
> In inotify.h the functions need to be marked static inline
> rather than just static or else there a number of new compiler warnings.
>
> I have addressed this for now, but if anything else comes up or if you
> resend this patch I would appreciate it if you add the static inline
> notations in your internal copy of the patch.
Okay, I will keep this in mind. Btw, do you compile with W=1 to get
those warnings, since I don't get them when I just run plain make?
>
> Thank you,
> Eric Biederman
>
>
>> diff --git a/fs/notify/inotify/inotify.h b/fs/notify/inotify/inotify.h
>> index ed855ef6f077..b5536f8ad3e0 100644
>> --- a/fs/notify/inotify/inotify.h
>> +++ b/fs/notify/inotify/inotify.h
>> @@ -30,3 +30,20 @@ extern int inotify_handle_event(struct fsnotify_group *group,
>> const unsigned char *file_name, u32 cookie);
>>
>> extern const struct fsnotify_ops inotify_fsnotify_ops;
>> +
>> +#ifdef CONFIG_INOTIFY_USER
>> +static void dec_inotify_instances(struct ucounts *ucounts)
>> +{
>> + dec_ucount(ucounts, UCOUNT_INOTIFY_INSTANCES);
>> +}
>> +
>> +static struct ucounts *inc_inotify_watches(struct ucounts *ucounts)
>> +{
>> + return inc_ucount(ucounts->ns, ucounts->uid, UCOUNT_INOTIFY_WATCHES);
>> +}
>> +
>> +static void dec_inotify_watches(struct ucounts *ucounts)
>> +{
>> + dec_ucount(ucounts, UCOUNT_INOTIFY_WATCHES);
>> +}
>> +#endif
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