Patch "x86: mm: move mmap_sem unlock from mm_fault_error() to caller" has been added to the 3.18-stable tree

[<gregkh@xxxxxxxxxxxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    x86: mm: move mmap_sem unlock from mm_fault_error() to caller

to the 3.18-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     x86-mm-move-mmap_sem-unlock-from-mm_fault_error-to-caller.patch
and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From 7fb08eca45270d0ae86e1ad9d39c40b7a55d0190 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Date: Mon, 15 Dec 2014 14:46:06 -0800
Subject: x86: mm: move mmap_sem unlock from mm_fault_error() to caller

From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>

commit 7fb08eca45270d0ae86e1ad9d39c40b7a55d0190 upstream.

This replaces four copies in various stages of mm_fault_error() handling
with just a single one.  It will also allow for more natural placement
of the unlocking after some further cleanup.

Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/x86/mm/fault.c |    8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -844,11 +844,8 @@ do_sigbus(struct pt_regs *regs, unsigned
 	  unsigned int fault)
 {
 	struct task_struct *tsk = current;
-	struct mm_struct *mm = tsk->mm;
 	int code = BUS_ADRERR;
 
-	up_read(&mm->mmap_sem);
-
 	/* Kernel mode? Handle exceptions or die: */
 	if (!(error_code & PF_USER)) {
 		no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
@@ -879,7 +876,6 @@ mm_fault_error(struct pt_regs *regs, uns
 	       unsigned long address, unsigned int fault)
 {
 	if (fatal_signal_pending(current) && !(error_code & PF_USER)) {
-		up_read(&current->mm->mmap_sem);
 		no_context(regs, error_code, address, 0, 0);
 		return;
 	}
@@ -887,14 +883,11 @@ mm_fault_error(struct pt_regs *regs, uns
 	if (fault & VM_FAULT_OOM) {
 		/* Kernel mode? Handle exceptions or die: */
 		if (!(error_code & PF_USER)) {
-			up_read(&current->mm->mmap_sem);
 			no_context(regs, error_code, address,
 				   SIGSEGV, SEGV_MAPERR);
 			return;
 		}
 
-		up_read(&current->mm->mmap_sem);
-
 		/*
 		 * We ran out of memory, call the OOM killer, and return the
 		 * userspace (which will retry the fault, or kill us if we got
@@ -1249,6 +1242,7 @@ good_area:
 		return;
 
 	if (unlikely(fault & VM_FAULT_ERROR)) {
+		up_read(&mm->mmap_sem);
 		mm_fault_error(regs, error_code, address, fault);
 		return;
 	}


Patches currently in stable-queue which might be from torvalds@xxxxxxxxxxxxxxxxxxxx are

queue-3.18/x86-mm-move-mmap_sem-unlock-from-mm_fault_error-to-caller.patch
queue-3.18/memcg-shmem-fix-shmem-migration-to-use-lrucare.patch
queue-3.18/nilfs2-fix-deadlock-of-segment-constructor-over-i_sync-flag.patch
queue-3.18/mm-pagewalk-call-pte_hole-for-vm_pfnmap-during-walk_page_range.patch
--
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