From 9057f884660dcde8ec600c27cf7b489a01ead67e Mon Sep 17 00:00:00 2001 From: Davidlohr Bueso Date: Thu, 26 Jun 2014 10:42:44 +1000 Subject: [PATCH] m68k: call find_vma with the mmap_sem held in sys_cacheflush() 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: Geert Uytterhoeven Signed-off-by: Andrew Morton --- arch/m68k/kernel/sys_m68k.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/arch/m68k/kernel/sys_m68k.c b/arch/m68k/kernel/sys_m68k.c index 3a480b3df0d6..d2263a0bdc3d 100644 --- a/arch/m68k/kernel/sys_m68k.c +++ b/arch/m68k/kernel/sys_m68k.c @@ -376,7 +376,6 @@ cache_flush_060 (unsigned long addr, int scope, int cache, unsigned long len) asmlinkage int sys_cacheflush (unsigned long addr, int scope, int cache, unsigned long len) { - struct vm_area_struct *vma; int ret = -EINVAL; if (scope < FLUSH_SCOPE_LINE || scope > FLUSH_SCOPE_ALL || @@ -389,16 +388,23 @@ sys_cacheflush (unsigned long addr, int scope, int cache, unsigned long len) if (!capable(CAP_SYS_ADMIN)) goto out; } else { + struct vm_area_struct *vma; + bool invalid; + + /* Check for overflow. */ + if (addr + len < addr) + goto out; + /* * Verify that the specified address region actually belongs * to this process. */ - vma = find_vma (current->mm, addr); ret = -EINVAL; - /* Check for overflow. */ - if (addr + len < addr) - goto out; - if (vma == NULL || addr < vma->vm_start || addr + len > vma->vm_end) + down_read(¤t->mm->mmap_sem); + vma = find_vma(current->mm, addr); + invalid = !vma || addr < vma->vm_start || addr + len > vma->vm_end; + up_read(¤t->mm->mmap_sem); + if (invalid) goto out; } -- 2.39.5