Messages in this thread | | | Date | Wed, 28 Feb 2018 10:32:39 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH] x86: mce: fix kernel panic when check_interval is changed |
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On Mon, Feb 26, 2018 at 05:05:04AM +0900, Seunghun Han wrote: > >> It is a critical security problem because the attacker can make kernel panic > >> by writing a value to the check_interval file in userspace, and it can be > >> used for Denial-of-Service (DoS) attack. > > > > As only root can write to that file, it's not that critical of an issue, > > but yes, this is a problem. Nice find and fix.
This is still the wrong fix. You need to:
1. check the old value of check_interval in store_int_with_restart() and exit early if it is the same.
2. have mce_restart() grab a newly defined mutex, say, mce_sysfs_mutex or so, which synchronizes all CPUs so that their timers get deleted and reinitialized in the proper order.
Thx.
-- Regards/Gruss, Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
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