x86/mce: Fix siginfo_t->si_addr value for non-recoverable memory faults

In commit dad1743e5993f1 ("x86/mce: Only restart instruction after machine
check recovery if it is safe") we fixed mce_notify_process() to force a
signal to the current process if it was not restartable (RIPV bit not
set in MCG_STATUS). But doing it here means that the process doesn't
get told the virtual address of the fault via siginfo_t->si_addr. This
would prevent application level recovery from the fault.

Make a new MF_MUST_KILL flag bit for memory_failure() et al. to use so
that we will provide the right information with the signal.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Acked-by: Borislav Petkov <borislav.petkov@amd.com>
Cc: stable@kernel.org    # 3.4+

3 files changed, 13 insertions, 8 deletions

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index da27c5d2168..c46ed494f00 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -1186,6 +1186,7 @@ void mce_notify_process(void)
 {
         unsigned long pfn;
         struct mce_info *mi = mce_find_info();
+        int flags = MF_ACTION_REQUIRED;
 
         if (!mi)
                 mce_panic("Lost physical address for unconsumed uncorrectable error", NULL, NULL);
@@ -1200,8 +1201,9 @@ void mce_notify_process(void)
          * 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) {
+        if (!mi->restartable)
+                flags |= MF_MUST_KILL;
+        if (memory_failure(pfn, MCE_VECTOR, flags) < 0) {
                 pr_err("Memory error not recovered");
                 force_sig(SIGBUS, current);
         }
diff --git a/include/linux/mm.h b/include/linux/mm.h
index b36d08ce5c5..f9f279cf5b1 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1591,6 +1591,7 @@ void vmemmap_populate_print_last(void);
 enum mf_flags {
         MF_COUNT_INCREASED = 1 << 0,
         MF_ACTION_REQUIRED = 1 << 1,
+        MF_MUST_KILL = 1 << 2,
 };
 extern int memory_failure(unsigned long pfn, int trapno, int flags);
 extern void memory_failure_queue(unsigned long pfn, int trapno, int flags);
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index ab1e7145e29..de4ce705845 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -345,14 +345,14 @@ static void add_to_kill(struct task_struct *tsk, struct page *p,
  * Also when FAIL is set do a force kill because something went
  * wrong earlier.
  */
-static void kill_procs(struct list_head *to_kill, int doit, int trapno,
+static void kill_procs(struct list_head *to_kill, int forcekill, int trapno,
                           int fail, struct page *page, unsigned long pfn,
                           int flags)
 {
         struct to_kill *tk, *next;
 
         list_for_each_entry_safe (tk, next, to_kill, nd) {
-                if (doit) {
+                if (forcekill) {
                         /*
                          * In case something went wrong with munmapping
                          * make sure the process doesn't catch the
@@ -858,7 +858,7 @@ static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
         struct address_space *mapping;
         LIST_HEAD(tokill);
         int ret;
-        int kill = 1;
+        int kill = 1, forcekill;
         struct page *hpage = compound_head(p);
         struct page *ppage;
 
@@ -888,7 +888,7 @@ static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
          * be called inside page lock (it's recommended but not enforced).
          */
         mapping = page_mapping(hpage);
-        if (!PageDirty(hpage) && mapping &&
+        if (!(flags & MF_MUST_KILL) && !PageDirty(hpage) && mapping &&
             mapping_cap_writeback_dirty(mapping)) {
                 if (page_mkclean(hpage)) {
                         SetPageDirty(hpage);
@@ -965,12 +965,14 @@ static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
          * Now that the dirty bit has been propagated to the
          * struct page and all unmaps done we can decide if
          * killing is needed or not.  Only kill when the page
-         * was dirty, otherwise the tokill list is merely
+         * was dirty or the process is not restartable,
+         * otherwise the tokill list is merely
          * freed.  When there was a problem unmapping earlier
          * use a more force-full uncatchable kill to prevent
          * any accesses to the poisoned memory.
          */
-        kill_procs(&tokill, !!PageDirty(ppage), trapno,
+        forcekill = PageDirty(ppage) || (flags & MF_MUST_KILL);
+        kill_procs(&tokill, forcekill, trapno,
                       ret != SWAP_SUCCESS, p, pfn, flags);
 
         return ret;