From b951242a4f633462b9766171bc5be8a8dc3f3e12 Mon Sep 17 00:00:00 2001
From: Davidlohr Bueso <davidlohr@hp.com>
Date: Fri, 6 Jun 2014 14:38:10 -0700
Subject: [PATCH] blackfin/ptrace: call find_vma with the mmap_sem held
Performing vma lookups without taking the mm->mmap_sem is asking for
trouble. While doing the search, the vma in question can be modified or
even removed before returning to the caller. Take the lock (shared) in
order to avoid races while iterating through the vmacache and/or rbtree.
Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
Cc: Steven Miao <realmz6@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
arch/blackfin/kernel/ptrace.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/arch/blackfin/kernel/ptrace.c b/arch/blackfin/kernel/ptrace.c
index e1f88e028cfe6..8b8fe671b1a6d 100644
--- a/arch/blackfin/kernel/ptrace.c
+++ b/arch/blackfin/kernel/ptrace.c
@@ -117,6 +117,7 @@ put_reg(struct task_struct *task, unsigned long regno, unsigned long data)
int
is_user_addr_valid(struct task_struct *child, unsigned long start, unsigned long len)
{
+ bool valid;
struct vm_area_struct *vma;
struct sram_list_struct *sraml;
@@ -124,9 +125,12 @@ is_user_addr_valid(struct task_struct *child, unsigned long start, unsigned long
if (start + len < start)
return -EIO;
+ down_read(&child->mm->mmap_sem);
vma = find_vma(child->mm, start);
- if (vma && start >= vma->vm_start && start + len <= vma->vm_end)
- return 0;
+ valid = vma && start >= vma->vm_start && start + len <= vma->vm_end;
+ up_read(&child->mm->mmap_sem);
+ if (valid)
+ return 0;
for (sraml = child->mm->context.sram_list; sraml; sraml = sraml->next)
if (start >= (unsigned long)sraml->addr
--
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