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x86/{fault,efi}: Fix and rename efi_recover_from_page_fault()

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efi_recover_from_page_fault() doesn't recover -- it does a special EFI
mini-oops.  Rename it to make it clear that it crashes.

While renaming it, I noticed a blatant bug: a page fault oops in a
different thread happening concurrently with an EFI runtime service call
would be misinterpreted as an EFI page fault.  Fix that.

This isn't quite exact. The situation could be improved by using a
special CS for calls into EFI.

 [ bp: Massage commit message and simplify in interrupt check. ]

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/f43b1e80830dc78ed60ed8b0826f4f189254570c.1612924255.git.luto@kernel.org
This commit is contained in:
Andy Lutomirski 2021-02-09 18:33:46 -08:00 • committed by Borislav Petkov
parent ca24728378
commit c46f52231e
3 changed files with 20 additions and 11 deletions
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11
arch/x86/mm/fault.c
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@ -16,7 +16,7 @@
#include <linux/prefetch.h> /* prefetchw */
#include <linux/context_tracking.h> /* exception_enter(), ... */
#include <linux/uaccess.h> /* faulthandler_disabled() */
#include <linux/efi.h> /* efi_recover_from_page_fault()*/
#include <linux/efi.h> /* efi_crash_gracefully_on_page_fault()*/
#include <linux/mm_types.h>
#include <asm/cpufeature.h> /* boot_cpu_has, ... */
@ -25,7 +25,7 @@
#include <asm/vsyscall.h> /* emulate_vsyscall */
#include <asm/vm86.h> /* struct vm86 */
#include <asm/mmu_context.h> /* vma_pkey() */
#include <asm/efi.h> /* efi_recover_from_page_fault()*/
#include <asm/efi.h> /* efi_crash_gracefully_on_page_fault()*/
#include <asm/desc.h> /* store_idt(), ... */
#include <asm/cpu_entry_area.h> /* exception stack */
#include <asm/pgtable_areas.h> /* VMALLOC_START, ... */
@ -701,11 +701,12 @@ page_fault_oops(struct pt_regs *regs, unsigned long error_code,
#endif
/*
* Buggy firmware could access regions which might page fault, try to
* recover from such faults.
* Buggy firmware could access regions which might page fault. If
* this happens, EFI has a special OOPS path that will try to
* avoid hanging the system.
*/
if (IS_ENABLED(CONFIG_EFI))
efi_recover_from_page_fault(address);
efi_crash_gracefully_on_page_fault(address);
oops:
/*