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+

1 files changed, 8 insertions, 6 deletions

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index ab1e7145e290..de4ce7058450 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;