Messages in this thread | | | Date | Thu, 23 Apr 2015 23:10:15 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH] x86/asm/entry/32: Restore %ss before SYSRETL if necessary |
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On Thu, Apr 23, 2015 at 10:01:16PM +0200, Denys Vlasenko wrote: > Naturally, CS can't be NULL, and up until today > I thought SS also can't. But the bit is probably implemented > for all eight cached descriptors.
There's this section about NULL selector in APM v2. It says that NULL selectors are used to invalidate segment registers and software can load a NULL selector in SS in CPL0.
So, if an interrupt happens and as you quoted earlier that SS gets set to NULL as a result of an interrupt, there's that SS leak causing the SS exception.
-- Regards/Gruss, Boris.
ECO tip #101: Trim your mails when you reply. --
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