linux-kernel - [PATCH 3.15 027/139] mm/memory-failure.c-failure: send right signal code to correct thread

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Message-Id: <20140628174606.649752335@linuxfoundation.org>
Date:	Sat, 28 Jun 2014 10:46:28 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Tony Luck <tony.luck@...el.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Otto Bruggeman <otto.g.bruggeman@...el.com>,
	Andi Kleen <andi@...stfloor.org>, Borislav Petkov <bp@...e.de>,
	Chen Gong <gong.chen@...ux.jf.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 3.15 027/139] mm/memory-failure.c-failure: send right signal code to correct thread

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

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

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

commit a70ffcac741d31a406c1d2b832ae43d658e7e1cf upstream.

When a thread in a multi-threaded application hits a machine check because
of an uncorrectable error in memory - we want to send the SIGBUS with
si.si_code = BUS_MCEERR_AR to that thread.  Currently we fail to do that
if the active thread is not the primary thread in the process.
collect_procs() just finds primary threads and this test:

	if ((flags & MF_ACTION_REQUIRED) && t == current) {

will see that the thread we found isn't the current thread and so send a
si.si_code = BUS_MCEERR_AO to the primary (and nothing to the active
thread at this time).

We can fix this by checking whether "current" shares the same mm with the
process that collect_procs() said owned the page.  If so, we send the
SIGBUS to current (with code BUS_MCEERR_AR).

Signed-off-by: Tony Luck <tony.luck@...el.com>
Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Reported-by: Otto Bruggeman <otto.g.bruggeman@...el.com>
Cc: Andi Kleen <andi@...stfloor.org>
Cc: Borislav Petkov <bp@...e.de>
Cc: Chen Gong <gong.chen@...ux.jf.intel.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 mm/memory-failure.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -204,9 +204,9 @@ static int kill_proc(struct task_struct
 #endif
 	si.si_addr_lsb = compound_order(compound_head(page)) + PAGE_SHIFT;
 
-	if ((flags & MF_ACTION_REQUIRED) && t == current) {
+	if ((flags & MF_ACTION_REQUIRED) && t->mm == current->mm) {
 		si.si_code = BUS_MCEERR_AR;
-		ret = force_sig_info(SIGBUS, &si, t);
+		ret = force_sig_info(SIGBUS, &si, current);
 	} else {
 		/*
 		 * Don't use force here, it's convenient if the signal


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