The following commit has been merged into the x86/mm branch of tip: Commit-ID: 9020d3956317d052cdddd43e55acdd2970344192 Gitweb: https://git.kernel.org/tip/9020d3956317d052cdddd43e55acdd2970344192 Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx> AuthorDate: Tue, 21 Apr 2020 11:20:31 +02:00 Committer: Borislav Petkov <bp@xxxxxxx> CommitterDate: Fri, 24 Apr 2020 19:12:56 +02:00 x86/alternatives: Move temporary_mm helpers into C The only user of these inlines is the text poke code and this must not be exposed to the world. No functional change. Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Reviewed-by: Alexandre Chartre <alexandre.chartre@xxxxxxxxxx> Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Link: https://lkml.kernel.org/r/20200421092559.139069561@xxxxxxxxxxxxx --- arch/x86/include/asm/mmu_context.h | 55 +----------------------------- arch/x86/kernel/alternative.c | 55 +++++++++++++++++++++++++++++- 2 files changed, 55 insertions(+), 55 deletions(-) diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h index 2985d06..4756214 100644 --- a/arch/x86/include/asm/mmu_context.h +++ b/arch/x86/include/asm/mmu_context.h @@ -215,59 +215,4 @@ static inline bool arch_vma_access_permitted(struct vm_area_struct *vma, unsigned long __get_current_cr3_fast(void); -typedef struct { - struct mm_struct *mm; -} temp_mm_state_t; - -/* - * Using a temporary mm allows to set temporary mappings that are not accessible - * by other CPUs. Such mappings are needed to perform sensitive memory writes - * that override the kernel memory protections (e.g., W^X), without exposing the - * temporary page-table mappings that are required for these write operations to - * other CPUs. Using a temporary mm also allows to avoid TLB shootdowns when the - * mapping is torn down. - * - * Context: The temporary mm needs to be used exclusively by a single core. To - * harden security IRQs must be disabled while the temporary mm is - * loaded, thereby preventing interrupt handler bugs from overriding - * the kernel memory protection. - */ -static inline temp_mm_state_t use_temporary_mm(struct mm_struct *mm) -{ - temp_mm_state_t temp_state; - - lockdep_assert_irqs_disabled(); - temp_state.mm = this_cpu_read(cpu_tlbstate.loaded_mm); - switch_mm_irqs_off(NULL, mm, current); - - /* - * If breakpoints are enabled, disable them while the temporary mm is - * used. Userspace might set up watchpoints on addresses that are used - * in the temporary mm, which would lead to wrong signals being sent or - * crashes. - * - * Note that breakpoints are not disabled selectively, which also causes - * kernel breakpoints (e.g., perf's) to be disabled. This might be - * undesirable, but still seems reasonable as the code that runs in the - * temporary mm should be short. - */ - if (hw_breakpoint_active()) - hw_breakpoint_disable(); - - return temp_state; -} - -static inline void unuse_temporary_mm(temp_mm_state_t prev_state) -{ - lockdep_assert_irqs_disabled(); - switch_mm_irqs_off(NULL, prev_state.mm, current); - - /* - * Restore the breakpoints if they were disabled before the temporary mm - * was loaded. - */ - if (hw_breakpoint_active()) - hw_breakpoint_restore(); -} - #endif /* _ASM_X86_MMU_CONTEXT_H */ diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 7867dfb..cd61797 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -783,6 +783,61 @@ void __init_or_module text_poke_early(void *addr, const void *opcode, } } +typedef struct { + struct mm_struct *mm; +} temp_mm_state_t; + +/* + * Using a temporary mm allows to set temporary mappings that are not accessible + * by other CPUs. Such mappings are needed to perform sensitive memory writes + * that override the kernel memory protections (e.g., W^X), without exposing the + * temporary page-table mappings that are required for these write operations to + * other CPUs. Using a temporary mm also allows to avoid TLB shootdowns when the + * mapping is torn down. + * + * Context: The temporary mm needs to be used exclusively by a single core. To + * harden security IRQs must be disabled while the temporary mm is + * loaded, thereby preventing interrupt handler bugs from overriding + * the kernel memory protection. + */ +static inline temp_mm_state_t use_temporary_mm(struct mm_struct *mm) +{ + temp_mm_state_t temp_state; + + lockdep_assert_irqs_disabled(); + temp_state.mm = this_cpu_read(cpu_tlbstate.loaded_mm); + switch_mm_irqs_off(NULL, mm, current); + + /* + * If breakpoints are enabled, disable them while the temporary mm is + * used. Userspace might set up watchpoints on addresses that are used + * in the temporary mm, which would lead to wrong signals being sent or + * crashes. + * + * Note that breakpoints are not disabled selectively, which also causes + * kernel breakpoints (e.g., perf's) to be disabled. This might be + * undesirable, but still seems reasonable as the code that runs in the + * temporary mm should be short. + */ + if (hw_breakpoint_active()) + hw_breakpoint_disable(); + + return temp_state; +} + +static inline void unuse_temporary_mm(temp_mm_state_t prev_state) +{ + lockdep_assert_irqs_disabled(); + switch_mm_irqs_off(NULL, prev_state.mm, current); + + /* + * Restore the breakpoints if they were disabled before the temporary mm + * was loaded. + */ + if (hw_breakpoint_active()) + hw_breakpoint_restore(); +} + __ro_after_init struct mm_struct *poking_mm; __ro_after_init unsigned long poking_addr;
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