From dad1743e5993f19b3d7e7bd0fb35dc45b5326626 Mon Sep 17 00:00:00 2001 From: Tony Luck Date: Mon, 14 May 2012 15:07:48 -0700 Subject: [PATCH] x86/mce: Only restart instruction after machine check recovery if it is safe MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Section 15.3.1.2 of the software developer manual has this to say about the RIPV bit in the IA32_MCG_STATUS register: RIPV (restart IP valid) flag, bit 0 — Indicates (when set) that program execution can be restarted reliably at the instruction pointed to by the instruction pointer pushed on the stack when the machine-check exception is generated. When clear, the program cannot be reliably restarted at the pushed instruction pointer. We need to save the state of this bit in do_machine_check() and use it in mce_notify_process() to force a signal; even if memory_failure() says it made a complete recovery ... e.g. replaced a clean LRU page. Acked-by: Borislav Petkov Signed-off-by: Tony Luck --- arch/x86/kernel/cpu/mcheck/mce.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c index d086a09c087d..11c9166c3337 100644 --- a/arch/x86/kernel/cpu/mcheck/mce.c +++ b/arch/x86/kernel/cpu/mcheck/mce.c @@ -945,9 +945,10 @@ struct mce_info { atomic_t inuse; struct task_struct *t; __u64 paddr; + int restartable; } mce_info[MCE_INFO_MAX]; -static void mce_save_info(__u64 addr) +static void mce_save_info(__u64 addr, int c) { struct mce_info *mi; @@ -955,6 +956,7 @@ static void mce_save_info(__u64 addr) if (atomic_cmpxchg(&mi->inuse, 0, 1) == 0) { mi->t = current; mi->paddr = addr; + mi->restartable = c; return; } } @@ -1130,7 +1132,7 @@ void do_machine_check(struct pt_regs *regs, long error_code) mce_panic("Fatal machine check on current CPU", &m, msg); if (worst == MCE_AR_SEVERITY) { /* schedule action before return to userland */ - mce_save_info(m.addr); + mce_save_info(m.addr, m.mcgstatus & MCG_STATUS_RIPV); set_thread_flag(TIF_MCE_NOTIFY); } else if (kill_it) { force_sig(SIGBUS, current); @@ -1179,7 +1181,13 @@ void mce_notify_process(void) pr_err("Uncorrected hardware memory error in user-access at %llx", mi->paddr); - if (memory_failure(pfn, MCE_VECTOR, MF_ACTION_REQUIRED) < 0) { + /* + * We must call memory_failure() here even if the current process is + * doomed. We still need to mark the page as poisoned and alert any + * other users of the page. + */ + if (memory_failure(pfn, MCE_VECTOR, MF_ACTION_REQUIRED) < 0 || + mi->restartable == 0) { pr_err("Memory error not recovered"); force_sig(SIGBUS, current); } -- 2.20.1