From 6802dc374de2b829cff181168216c0f17c4a64f7 Mon Sep 17 00:00:00 2001 From: Aili Yao Date: Tue, 10 Aug 2021 16:27:19 +0800 Subject: [PATCH] mm,hwpoison: return -EHWPOISON to denote that the page has already been poisoned mainline inclusion from mainline-v5.13 commit 47af12bae17f99b5e77f8651cb7f3e1877610acf category: bugfix bugzilla: 175120 CVE: NA ------------------------------------------------- When memory_failure() is called with MF_ACTION_REQUIRED on the page that has already been hwpoisoned, memory_failure() could fail to send SIGBUS to the affected process, which results in infinite loop of MCEs. Currently memory_failure() returns 0 if it's called for already hwpoisoned page, then the caller, kill_me_maybe(), could return without sending SIGBUS to current process. An action required MCE is raised when the current process accesses to the broken memory, so no SIGBUS means that the current process continues to run and access to the error page again soon, so running into MCE loop. This issue can arise for example in the following scenarios: - Two or more threads access to the poisoned page concurrently. If local MCE is enabled, MCE handler independently handles the MCE events. So there's a race among MCE events, and the second or latter threads fall into the situation in question. - If there was a precedent memory error event and memory_failure() for the event failed to unmap the error page for some reason, the subsequent memory access to the error page triggers the MCE loop situation. To fix the issue, make memory_failure() return an error code when the error page has already been hwpoisoned. This allows memory error handler to control how it sends signals to userspace. And make sure that any process touching a hwpoisoned page should get a SIGBUS even in "already hwpoisoned" path of memory_failure() as is done in page fault path. Link: https://lkml.kernel.org/r/20210521030156.2612074-3-nao.horiguchi@gmail.com Signed-off-by: Aili Yao Signed-off-by: Naoya Horiguchi Reviewed-by: Oscar Salvador Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Borislav Petkov Cc: David Hildenbrand Cc: Jue Wang Cc: Tony Luck Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Nanyong Sun Reviewed-by: Chen Wandun Signed-off-by: Yang Yingliang --- mm/memory-failure.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 54e93c679cec..77f29dd9e5c9 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -1094,7 +1094,7 @@ static int memory_failure_hugetlb(unsigned long pfn, int flags) if (TestSetPageHWPoison(head)) { pr_err("Memory failure: %#lx: already hardware poisoned\n", pfn); - return 0; + return -EHWPOISON; } num_poisoned_pages_inc(); @@ -1286,6 +1286,7 @@ int memory_failure(unsigned long pfn, int flags) if (TestSetPageHWPoison(p)) { pr_err("Memory failure: %#lx: already hardware poisoned\n", pfn); + res = -EHWPOISON; goto unlock_mutex; } -- GitLab