hulk inclusion category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I69VF6 CVE: NA -------------------------------- If kdump is enabled, when using mce_inject to inject errors, EFI boot loader would decompress & load second kernel for saving the vmcore file. For normal errors that is fine. However, in the MCE case, the panic CPU that firstly enters into mce_panic() is running within NMI interrupt context, and the processor blocks delivery of subsequent NMIs until the next execution of the IRET instruction. When the panic CPU takes long time in the panic processing route, and causes the watchdog timeout, at this moment, the processor already receives NMI interrupt in the background. In the reproducer sequence below, panic CPU would run into EFI loader and raise page fault exception (like visiting `vidmem` variable when attempting to call debug_putstr()), the CPU would execute IRET instruction when it exits from the page fault handler. But the loader never registers handler for NMI vector in IDT, lack of vector handler would cause reboot, which interrupts kdump procedure and fails to save the vmcore file. Here is steps to reproduce the above issue (it's sporadic): 1. # cat uncorrected CPU 1 BANK 4 STATUS uncorrected 0xc0 MCGSTATUS EIPV MCIP ADDR 0x1234 RIP 0xdeadbabe RAISINGCPU 0 MCGCAP SER CMCI TES 0x6 2. # modprobe mce_inject 3. # mce-inject uncorrected For increasing the probability of reproduction of this issue, there are two ways to increase the probability of the bug: 1. modify the threshold value of watchdog (increase NMI frequency); 2. and/or add delays before panic() in mce_panic() and modify PANIC_TIMEOUT macro; Fixes: ca0e22d4f011 ("x86/boot/compressed/64: Always switch to own page table") Signed-off-by: Zeng Heng <zengheng4@huawei.com> [ Tidy up changelog, add comments. ] Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20230110102745.2514694-1-zengheng4@huawei.com --- arch/x86/boot/compressed/ident_map_64.c | 13 +++++++++++++ arch/x86/boot/compressed/idt_64.c | 1 + arch/x86/boot/compressed/idt_handlers_64.S | 1 + arch/x86/boot/compressed/misc.h | 1 + 4 files changed, 16 insertions(+) diff --git a/arch/x86/boot/compressed/ident_map_64.c b/arch/x86/boot/compressed/ident_map_64.c index 08f93b0401bb..dc0ec27ff1b1 100644 --- a/arch/x86/boot/compressed/ident_map_64.c +++ b/arch/x86/boot/compressed/ident_map_64.c @@ -385,3 +385,16 @@ void do_boot_page_fault(struct pt_regs *regs, unsigned long error_code) */ kernel_add_identity_map(address, end); } + +void do_boot_nmi_fault(struct pt_regs *regs, unsigned long error_code) +{ + /* + * Default boot loader placeholder fault handler - there's no real + * kernel running yet, so there's not much we can do - but NMIs + * can arrive in a kdump scenario, for example by the NMI watchdog. + * + * Not having any handler would cause the CPU to silently reboot, + * so we do the second-worst thing here and ignore the NMI. + */ + debug_putstr("nmi fault raise\n"); +} diff --git a/arch/x86/boot/compressed/idt_64.c b/arch/x86/boot/compressed/idt_64.c index 3cdf94b41456..0f3318bdf262 100644 --- a/arch/x86/boot/compressed/idt_64.c +++ b/arch/x86/boot/compressed/idt_64.c @@ -60,6 +60,7 @@ void load_stage2_idt(void) { boot_idt_desc.address = (unsigned long)boot_idt; + set_idt_entry(X86_TRAP_NMI, boot_nmi_fault); set_idt_entry(X86_TRAP_PF, boot_page_fault); #ifdef CONFIG_AMD_MEM_ENCRYPT diff --git a/arch/x86/boot/compressed/idt_handlers_64.S b/arch/x86/boot/compressed/idt_handlers_64.S index 22890e199f5b..2aef8e1b515b 100644 --- a/arch/x86/boot/compressed/idt_handlers_64.S +++ b/arch/x86/boot/compressed/idt_handlers_64.S @@ -69,6 +69,7 @@ SYM_FUNC_END(\name) .text .code64 +EXCEPTION_HANDLER boot_nmi_fault do_boot_nmi_fault error_code=0 EXCEPTION_HANDLER boot_page_fault do_boot_page_fault error_code=1 #ifdef CONFIG_AMD_MEM_ENCRYPT diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h index cc70d3fb9049..f06fb86b83bc 100644 --- a/arch/x86/boot/compressed/misc.h +++ b/arch/x86/boot/compressed/misc.h @@ -196,6 +196,7 @@ static inline void cleanup_exception_handling(void) { } #endif /* IDT Entry Points */ +void boot_nmi_fault(void); void boot_page_fault(void); void boot_stage1_vc(void); void boot_stage2_vc(void); -- 2.25.1