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blackfin/ptrace: call find_vma with the mmap_sem held

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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>
This commit is contained in:
Davidlohr Bueso 2014-06-06 14:38:10 -07:00 committed by Linus Torvalds
parent cccad5b983
commit b951242a4f
1 changed files with 6 additions and 2 deletions
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8
arch/blackfin/kernel/ptrace.c
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@ -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