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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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Thomas Gleixner
942c5864de
commit9bfecd0583upstream. While digesting the XSAVE-related horrors which got introduced with the supervisor/user split, the recent addition of ENQCMD-related functionality got on the radar and turned out to be similarly broken. update_pasid(), which is only required when X86_FEATURE_ENQCMD is available, is invoked from two places: 1) From switch_to() for the incoming task 2) Via a SMP function call from the IOMMU/SMV code #1 is half-ways correct as it hacks around the brokenness of get_xsave_addr() by enforcing the state to be 'present', but all the conditionals in that code are completely pointless for that. Also the invocation is just useless overhead because at that point it's guaranteed that TIF_NEED_FPU_LOAD is set on the incoming task and all of this can be handled at return to user space. #2 is broken beyond repair. The comment in the code claims that it is safe to invoke this in an IPI, but that's just wishful thinking. FPU state of a running task is protected by fregs_lock() which is nothing else than a local_bh_disable(). As BH-disabled regions run usually with interrupts enabled the IPI can hit a code section which modifies FPU state and there is absolutely no guarantee that any of the assumptions which are made for the IPI case is true. Also the IPI is sent to all CPUs in mm_cpumask(mm), but the IPI is invoked with a NULL pointer argument, so it can hit a completely unrelated task and unconditionally force an update for nothing. Worse, it can hit a kernel thread which operates on a user space address space and set a random PASID for it. The offending commit does not cleanly revert, but it's sufficient to force disable X86_FEATURE_ENQCMD and to remove the broken update_pasid() code to make this dysfunctional all over the place. Anything more complex would require more surgery and none of the related functions outside of the x86 core code are blatantly wrong, so removing those would be overkill. As nothing enables the PASID bit in the IA32_XSS MSR yet, which is required to make this actually work, this cannot result in a regression except for related out of tree train-wrecks, but they are broken already today. Fixes:20f0afd1fb("x86/mmu: Allocate/free a PASID") Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Andy Lutomirski <luto@kernel.org> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/87mtsd6gr9.ffs@nanos.tec.linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
88 lines
2.4 KiB
C
88 lines
2.4 KiB
C
#ifndef _ASM_X86_DISABLED_FEATURES_H
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#define _ASM_X86_DISABLED_FEATURES_H
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/* These features, although they might be available in a CPU
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* will not be used because the compile options to support
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* them are not present.
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*
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* This code allows them to be checked and disabled at
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* compile time without an explicit #ifdef. Use
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* cpu_feature_enabled().
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*/
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#ifdef CONFIG_X86_SMAP
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# define DISABLE_SMAP 0
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#else
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# define DISABLE_SMAP (1<<(X86_FEATURE_SMAP & 31))
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#endif
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#ifdef CONFIG_X86_UMIP
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# define DISABLE_UMIP 0
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#else
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# define DISABLE_UMIP (1<<(X86_FEATURE_UMIP & 31))
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#endif
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#ifdef CONFIG_X86_64
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# define DISABLE_VME (1<<(X86_FEATURE_VME & 31))
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# define DISABLE_K6_MTRR (1<<(X86_FEATURE_K6_MTRR & 31))
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# define DISABLE_CYRIX_ARR (1<<(X86_FEATURE_CYRIX_ARR & 31))
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# define DISABLE_CENTAUR_MCR (1<<(X86_FEATURE_CENTAUR_MCR & 31))
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# define DISABLE_PCID 0
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#else
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# define DISABLE_VME 0
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# define DISABLE_K6_MTRR 0
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# define DISABLE_CYRIX_ARR 0
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# define DISABLE_CENTAUR_MCR 0
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# define DISABLE_PCID (1<<(X86_FEATURE_PCID & 31))
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#endif /* CONFIG_X86_64 */
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#ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
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# define DISABLE_PKU 0
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# define DISABLE_OSPKE 0
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#else
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# define DISABLE_PKU (1<<(X86_FEATURE_PKU & 31))
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# define DISABLE_OSPKE (1<<(X86_FEATURE_OSPKE & 31))
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#endif /* CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS */
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#ifdef CONFIG_X86_5LEVEL
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# define DISABLE_LA57 0
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#else
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# define DISABLE_LA57 (1<<(X86_FEATURE_LA57 & 31))
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#endif
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#ifdef CONFIG_PAGE_TABLE_ISOLATION
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# define DISABLE_PTI 0
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#else
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# define DISABLE_PTI (1 << (X86_FEATURE_PTI & 31))
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#endif
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/* Force disable because it's broken beyond repair */
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#define DISABLE_ENQCMD (1 << (X86_FEATURE_ENQCMD & 31))
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/*
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* Make sure to add features to the correct mask
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*/
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#define DISABLED_MASK0 (DISABLE_VME)
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#define DISABLED_MASK1 0
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#define DISABLED_MASK2 0
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#define DISABLED_MASK3 (DISABLE_CYRIX_ARR|DISABLE_CENTAUR_MCR|DISABLE_K6_MTRR)
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#define DISABLED_MASK4 (DISABLE_PCID)
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#define DISABLED_MASK5 0
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#define DISABLED_MASK6 0
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#define DISABLED_MASK7 (DISABLE_PTI)
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#define DISABLED_MASK8 0
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#define DISABLED_MASK9 (DISABLE_SMAP)
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#define DISABLED_MASK10 0
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#define DISABLED_MASK11 0
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#define DISABLED_MASK12 0
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#define DISABLED_MASK13 0
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#define DISABLED_MASK14 0
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#define DISABLED_MASK15 0
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#define DISABLED_MASK16 (DISABLE_PKU|DISABLE_OSPKE|DISABLE_LA57|DISABLE_UMIP| \
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DISABLE_ENQCMD)
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#define DISABLED_MASK17 0
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#define DISABLED_MASK18 0
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#define DISABLED_MASK_CHECK BUILD_BUG_ON_ZERO(NCAPINTS != 19)
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#endif /* _ASM_X86_DISABLED_FEATURES_H */
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