From: Davidlohr Bueso Date: Fri, 6 Jun 2014 21:38:10 +0000 (-0700) Subject: blackfin/ptrace: call find_vma with the mmap_sem held X-Git-Tag: v3.16-rc1~82^2~4^2~25 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=b951242a4f633462b9766171bc5be8a8dc3f3e12;p=linux.git 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 Cc: Steven Miao Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/arch/blackfin/kernel/ptrace.c b/arch/blackfin/kernel/ptrace.c index e1f88e028cfe..8b8fe671b1a6 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