Commit 171936dd authored by Tony Luck's avatar Tony Luck Committed by Linus Torvalds
Browse files

mm/memory-failure: use a mutex to avoid memory_failure() races 

Patch series "mm,hwpoison: fix sending SIGBUS for Action Required MCE", v5.

I wrote this patchset to materialize what I think is the current
allowable solution mentioned by the previous discussion [1].  I simply
borrowed Tony's mutex patch and Aili's return code patch, then I queued
another one to find error virtual address in the best effort manner.  I
know that this is not a perfect solution, but should work for some
typical case.

[1]: https://lore.kernel.org/linux-mm/20210331192540.2141052f@alex-virtual-machine/

This patch (of 2):

There can be races when multiple CPUs consume poison from the same page.
The first into memory_failure() atomically sets the HWPoison page flag
and begins hunting for tasks that map this page.  Eventually it
invalidates those mappings and may send a SIGBUS to the affected tasks.

But while all that work is going on, other CPUs see a "success" return
code from memory_failure() and so they believe the error has been
handled and continue executing.

Fix by wrapping most of the internal parts of memory_failure() in a
mutex.

[akpm@linux-foundation.org: make mf_mutex local to memory_failure()]

Link: https://lkml.kernel.org/r/20210521030156.2612074-1-nao.horiguchi@gmail.com
Link: https://lkml.kernel.org/r/20210521030156.2612074-2-nao.horiguchi@gmail.com


Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
Signed-off-by: default avatarNaoya Horiguchi <naoya.horiguchi@nec.com>
Reviewed-by: default avatarBorislav Petkov <bp@suse.de>
Reviewed-by: default avatarOscar Salvador <osalvador@suse.de>
Cc: Aili Yao <yaoaili@kingsoft.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jue Wang <juew@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent fe19bd3d

mm/memory-failure.c

+23 −13
Original line number Diff line number Diff line
@@ -1429,9 +1429,10 @@ int memory_failure(unsigned long pfn, int flags) 
	struct page *hpage;

	struct page *orig_head;

	struct dev_pagemap *pgmap;

	int res;

	int res = 0;

	unsigned long page_flags;

	bool retry = true;

	static DEFINE_MUTEX(mf_mutex);



	if (!sysctl_memory_failure_recovery)

		panic("Memory failure on page %lx", pfn);
@@ -1449,13 +1450,18 @@ int memory_failure(unsigned long pfn, int flags) 
		return -ENXIO;

	}



	mutex_lock(&mf_mutex);



try_again:

	if (PageHuge(p))

		return memory_failure_hugetlb(pfn, flags);

	if (PageHuge(p)) {

		res = memory_failure_hugetlb(pfn, flags);

		goto unlock_mutex;

	}



	if (TestSetPageHWPoison(p)) {

		pr_err("Memory failure: %#lx: already hardware poisoned\n",

			pfn);

		return 0;

		goto unlock_mutex;

	}



	orig_head = hpage = compound_head(p);
@@ -1488,17 +1494,19 @@ int memory_failure(unsigned long pfn, int flags) 
				res = MF_FAILED;

			}

			action_result(pfn, MF_MSG_BUDDY, res);

			return res == MF_RECOVERED ? 0 : -EBUSY;

			res = res == MF_RECOVERED ? 0 : -EBUSY;

		} else {

			action_result(pfn, MF_MSG_KERNEL_HIGH_ORDER, MF_IGNORED);

			return -EBUSY;

			res = -EBUSY;

		}

		goto unlock_mutex;

	}



	if (PageTransHuge(hpage)) {

		if (try_to_split_thp_page(p, "Memory Failure") < 0) {

			action_result(pfn, MF_MSG_UNSPLIT_THP, MF_IGNORED);

			return -EBUSY;

			res = -EBUSY;

			goto unlock_mutex;

		}

		VM_BUG_ON_PAGE(!page_count(p), p);

	}
@@ -1522,7 +1530,7 @@ int memory_failure(unsigned long pfn, int flags) 
	if (PageCompound(p) && compound_head(p) != orig_head) {

		action_result(pfn, MF_MSG_DIFFERENT_COMPOUND, MF_IGNORED);

		res = -EBUSY;

		goto out;

		goto unlock_page;

	}



	/*
@@ -1542,14 +1550,14 @@ int memory_failure(unsigned long pfn, int flags) 
		num_poisoned_pages_dec();

		unlock_page(p);

		put_page(p);

		return 0;

		goto unlock_mutex;

	}

	if (hwpoison_filter(p)) {

		if (TestClearPageHWPoison(p))

			num_poisoned_pages_dec();

		unlock_page(p);

		put_page(p);

		return 0;

		goto unlock_mutex;

	}



	/*
@@ -1573,7 +1581,7 @@ int memory_failure(unsigned long pfn, int flags) 
	if (!hwpoison_user_mappings(p, pfn, flags, &p)) {

		action_result(pfn, MF_MSG_UNMAP_FAILED, MF_IGNORED);

		res = -EBUSY;

		goto out;

		goto unlock_page;

	}



	/*
@@ -1582,13 +1590,15 @@ int memory_failure(unsigned long pfn, int flags) 
	if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) {

		action_result(pfn, MF_MSG_TRUNCATED_LRU, MF_IGNORED);

		res = -EBUSY;

		goto out;

		goto unlock_page;

	}



identify_page_state:

	res = identify_page_state(pfn, p, page_flags);

out:

unlock_page:

	unlock_page(p);

unlock_mutex:

	mutex_unlock(&mf_mutex);

	return res;

}

EXPORT_SYMBOL_GPL(memory_failure);