From 2cc624b0a7e68ba8957b18600181f7d5b0f3e1b6 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Tue, 9 Feb 2021 18:33:41 -0800 Subject: x86/fault: Split the OOPS code out from no_context() Not all callers of no_context() want to run exception fixups. Separate the OOPS code out from the fixup code in no_context(). Signed-off-by: Andy Lutomirski Signed-off-by: Borislav Petkov Link: https://lkml.kernel.org/r/450f8d8eabafb83a5df349108c8e5ea83a2f939d.1612924255.git.luto@kernel.org --- arch/x86/mm/fault.c | 116 ++++++++++++++++++++++++++++------------------------ 1 file changed, 62 insertions(+), 54 deletions(-) (limited to 'arch/x86/mm/fault.c') diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index cbb1a9754473..dbf6a940b03f 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -655,53 +655,20 @@ static void set_signal_archinfo(unsigned long address, } static noinline void -no_context(struct pt_regs *regs, unsigned long error_code, - unsigned long address, int signal, int si_code) +page_fault_oops(struct pt_regs *regs, unsigned long error_code, + unsigned long address) { - struct task_struct *tsk = current; unsigned long flags; int sig; if (user_mode(regs)) { /* - * This is an implicit supervisor-mode access from user - * mode. Bypass all the kernel-mode recovery code and just - * OOPS. + * Implicit kernel access from user mode? Skip the stack + * overflow and EFI special cases. */ goto oops; } - /* Are we prepared to handle this kernel fault? */ - if (fixup_exception(regs, X86_TRAP_PF, error_code, address)) { - /* - * Any interrupt that takes a fault gets the fixup. This makes - * the below recursive fault logic only apply to a faults from - * task context. - */ - if (in_interrupt()) - return; - - /* - * Per the above we're !in_interrupt(), aka. task context. - * - * In this case we need to make sure we're not recursively - * faulting through the emulate_vsyscall() logic. - */ - if (current->thread.sig_on_uaccess_err && signal) { - sanitize_error_code(address, &error_code); - - set_signal_archinfo(address, error_code); - - /* XXX: hwpoison faults will set the wrong code. */ - force_sig_fault(signal, si_code, (void __user *)address); - } - - /* - * Barring that, we can do the fixup and be happy. - */ - return; - } - #ifdef CONFIG_VMAP_STACK /* * Stack overflow? During boot, we can fault near the initial @@ -709,8 +676,8 @@ no_context(struct pt_regs *regs, unsigned long error_code, * that we're in vmalloc space to avoid this. */ if (is_vmalloc_addr((void *)address) && - (((unsigned long)tsk->stack - 1 - address < PAGE_SIZE) || - address - ((unsigned long)tsk->stack + THREAD_SIZE) < PAGE_SIZE)) { + (((unsigned long)current->stack - 1 - address < PAGE_SIZE) || + address - ((unsigned long)current->stack + THREAD_SIZE) < PAGE_SIZE)) { unsigned long stack = __this_cpu_ist_top_va(DF) - sizeof(void *); /* * We're likely to be running with very little stack space @@ -733,20 +700,6 @@ no_context(struct pt_regs *regs, unsigned long error_code, } #endif - /* - * 32-bit: - * - * Valid to do another page fault here, because if this fault - * had been triggered by is_prefetch fixup_exception would have - * handled it. - * - * 64-bit: - * - * Hall of shame of CPU/BIOS bugs. - */ - if (is_prefetch(regs, error_code, address)) - return; - /* * Buggy firmware could access regions which might page fault, try to * recover from such faults. @@ -763,7 +716,7 @@ oops: show_fault_oops(regs, error_code, address); - if (task_stack_end_corrupted(tsk)) + if (task_stack_end_corrupted(current)) printk(KERN_EMERG "Thread overran stack, or stack corrupted\n"); sig = SIGKILL; @@ -776,6 +729,61 @@ oops: oops_end(flags, regs, sig); } +static noinline void +no_context(struct pt_regs *regs, unsigned long error_code, + unsigned long address, int signal, int si_code) +{ + if (user_mode(regs)) { + /* + * This is an implicit supervisor-mode access from user + * mode. Bypass all the kernel-mode recovery code and just + * OOPS. + */ + goto oops; + } + + /* Are we prepared to handle this kernel fault? */ + if (fixup_exception(regs, X86_TRAP_PF, error_code, address)) { + /* + * Any interrupt that takes a fault gets the fixup. This makes + * the below recursive fault logic only apply to a faults from + * task context. + */ + if (in_interrupt()) + return; + + /* + * Per the above we're !in_interrupt(), aka. task context. + * + * In this case we need to make sure we're not recursively + * faulting through the emulate_vsyscall() logic. + */ + if (current->thread.sig_on_uaccess_err && signal) { + sanitize_error_code(address, &error_code); + + set_signal_archinfo(address, error_code); + + /* XXX: hwpoison faults will set the wrong code. */ + force_sig_fault(signal, si_code, (void __user *)address); + } + + /* + * Barring that, we can do the fixup and be happy. + */ + return; + } + + /* + * AMD erratum #91 manifests as a spurious page fault on a PREFETCH + * instruction. + */ + if (is_prefetch(regs, error_code, address)) + return; + +oops: + page_fault_oops(regs, error_code, address); +} + /* * Print out info about fatal segfaults, if the show_unhandled_signals * sysctl is set: -- cgit v1.2.3