[ 3.5.y.z extended stable ] Patch "ARM: missing ->mmap_sem around find_vma() in" has been added to staging queue

[Herton Ronaldo Krzesinski]

This is a note to let you know that I have just added a patch titled

    ARM: missing ->mmap_sem around find_vma() in

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Herton

------

>From 492f4fe1843c9a0fca453ba7a758033b170abfb5 Mon Sep 17 00:00:00 2001
From: Al Viro <viro at ZenIV.linux.org.uk>
Date: Sun, 16 Dec 2012 00:25:57 +0000
Subject: [PATCH 18/27] ARM: missing ->mmap_sem around find_vma() in
 swp_emulate.c

commit 7bf9b7bef881aac820bf1f2e9951a17b09bd7e04 upstream.

find_vma() is *not* safe when somebody else is removing vmas.  Not just
the return value might get bogus just as you are getting it (this instance
doesn't try to dereference the resulting vma), the search itself can get
buggered in rather spectacular ways.  IOW, ->mmap_sem really, really is
not optional here.

Signed-off-by: Al Viro <viro at zeniv.linux.org.uk>
Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
---
 arch/arm/kernel/swp_emulate.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm/kernel/swp_emulate.c b/arch/arm/kernel/swp_emulate.c
index df74518..ab1017b 100644
--- a/arch/arm/kernel/swp_emulate.c
+++ b/arch/arm/kernel/swp_emulate.c
@@ -109,10 +109,12 @@ static void set_segfault(struct pt_regs *regs, unsigned long addr)
 {
 	siginfo_t info;

+	down_read(&current->mm->mmap_sem);
 	if (find_vma(current->mm, addr) == NULL)
 		info.si_code = SEGV_MAPERR;
 	else
 		info.si_code = SEGV_ACCERR;
+	up_read(&current->mm->mmap_sem);

 	info.si_signo = SIGSEGV;
 	info.si_errno = 0;
--
1.7.9.5