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Subject[ 027/109] x86/mce: Fix siginfo_t->si_addr value for non-recoverable memory faults
Date
From: Greg KH <gregkh@linuxfoundation.org>

3.4-stable review patch. If anyone has any objections, please let me know.

------------------

From: Tony Luck <tony.luck@intel.com>

commit 6751ed65dc6642af64f7b8a440a75563c8aab7ae upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/kernel/cpu/mcheck/mce.c | 6 ++++--
include/linux/mm.h | 1 +
mm/memory-failure.c | 14 ++++++++------
3 files changed, 13 insertions(+), 8 deletions(-)

--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -1180,6 +1180,7 @@ 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);
@@ -1194,8 +1195,9 @@ 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);
}
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1595,6 +1595,7 @@ 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);
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -345,14 +345,14 @@ static void add_to_kill(struct task_stru
* 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
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
* 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
* 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;



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