From af5c40c6ee057c5354930abdc4d34be013d0e9e0 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 21 Apr 2020 11:20:40 +0200 Subject: [PATCH] x86/tlb: Uninline nmi_uaccess_okay() cpu_tlbstate is exported because various TLB-related functions need access to it, but cpu_tlbstate is sensitive information which should only be accessed by well-contained kernel functions and not be directly exposed to modules. nmi_access_ok() is the last inline function which requires access to cpu_tlbstate. Move it into the TLB code. No functional change. Signed-off-by: Thomas Gleixner Signed-off-by: Borislav Petkov Reviewed-by: Alexandre Chartre Acked-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200421092600.052543007@linutronix.de --- arch/x86/include/asm/tlbflush.h | 33 +-------------------------------- arch/x86/mm/tlb.c | 32 ++++++++++++++++++++++++++++++++ 2 files changed, 33 insertions(+), 32 deletions(-) diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h index 917deea058d5..1c17f5a6cb53 100644 --- a/arch/x86/include/asm/tlbflush.h +++ b/arch/x86/include/asm/tlbflush.h @@ -247,38 +247,7 @@ struct tlb_state { }; DECLARE_PER_CPU_SHARED_ALIGNED(struct tlb_state, cpu_tlbstate); -/* - * Blindly accessing user memory from NMI context can be dangerous - * if we're in the middle of switching the current user task or - * switching the loaded mm. It can also be dangerous if we - * interrupted some kernel code that was temporarily using a - * different mm. - */ -static inline bool nmi_uaccess_okay(void) -{ - struct mm_struct *loaded_mm = this_cpu_read(cpu_tlbstate.loaded_mm); - struct mm_struct *current_mm = current->mm; - - VM_WARN_ON_ONCE(!loaded_mm); - - /* - * The condition we want to check is - * current_mm->pgd == __va(read_cr3_pa()). This may be slow, though, - * if we're running in a VM with shadow paging, and nmi_uaccess_okay() - * is supposed to be reasonably fast. - * - * Instead, we check the almost equivalent but somewhat conservative - * condition below, and we rely on the fact that switch_mm_irqs_off() - * sets loaded_mm to LOADED_MM_SWITCHING before writing to CR3. - */ - if (loaded_mm != current_mm) - return false; - - VM_WARN_ON_ONCE(current_mm->pgd != __va(read_cr3_pa())); - - return true; -} - +bool nmi_uaccess_okay(void); #define nmi_uaccess_okay nmi_uaccess_okay void cr4_update_irqsoff(unsigned long set, unsigned long clear); diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index aabf8c7377e3..45426ae8e7d7 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -1094,6 +1094,38 @@ void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch) put_cpu(); } +/* + * Blindly accessing user memory from NMI context can be dangerous + * if we're in the middle of switching the current user task or + * switching the loaded mm. It can also be dangerous if we + * interrupted some kernel code that was temporarily using a + * different mm. + */ +bool nmi_uaccess_okay(void) +{ + struct mm_struct *loaded_mm = this_cpu_read(cpu_tlbstate.loaded_mm); + struct mm_struct *current_mm = current->mm; + + VM_WARN_ON_ONCE(!loaded_mm); + + /* + * The condition we want to check is + * current_mm->pgd == __va(read_cr3_pa()). This may be slow, though, + * if we're running in a VM with shadow paging, and nmi_uaccess_okay() + * is supposed to be reasonably fast. + * + * Instead, we check the almost equivalent but somewhat conservative + * condition below, and we rely on the fact that switch_mm_irqs_off() + * sets loaded_mm to LOADED_MM_SWITCHING before writing to CR3. + */ + if (loaded_mm != current_mm) + return false; + + VM_WARN_ON_ONCE(current_mm->pgd != __va(read_cr3_pa())); + + return true; +} + static ssize_t tlbflush_read_file(struct file *file, char __user *user_buf, size_t count, loff_t *ppos) {