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: Tony Luck <tony.luck@intel.com>
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Oscar 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 0143d32..a7fc1cd 100644 (file)
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -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 @@ try_again:
                                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 @@ try_again:
        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 @@ try_again:
                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 @@ try_again:
        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 @@ try_again:
        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);