From fe936dfc23fed3475b11067e8d9b70553eafcd9e Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Thu, 14 Apr 2011 15:22:10 -0700 Subject: [PATCH] mm: check that we have the right vma in __access_remote_vm() In __access_remote_vm() we need to check that we have found the right vma, not the following vma before we try to access it. Otherwise we might call the vma's access routine with an address which does not fall inside the vma. It was discovered on a current kernel but with an unreleased driver, from memory it was strace leading to a kernel bad access, but it obviously depends on what the access implementation does. Looking at other access implementations I only see: $ git grep -A 5 vm_operations|grep access arch/powerpc/platforms/cell/spufs/file.c- .access = spufs_mem_mmap_access, arch/x86/pci/i386.c- .access = generic_access_phys, drivers/char/mem.c- .access = generic_access_phys fs/sysfs/bin.c- .access = bin_access, The spufs one looks like it might behave badly given the wrong vma, it assumes vma->vm_file->private_data is a spu_context, and looks like it would probably blow up pretty quickly if it wasn't. generic_access_phys() only uses the vma to check vm_flags and get the mm, and then walks page tables using the address. So it should bail on the vm_flags check, or at worst let you access some other VM_IO mapping. And bin_access() just proxies to another access implementation. Signed-off-by: Michael Ellerman Reviewed-by: KOSAKI Motohiro Cc: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memory.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/memory.c b/mm/memory.c index b623a249918c..ce22a250926f 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3688,7 +3688,7 @@ static int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm, */ #ifdef CONFIG_HAVE_IOREMAP_PROT vma = find_vma(mm, addr); - if (!vma) + if (!vma || vma->vm_start > addr) break; if (vma->vm_ops && vma->vm_ops->access) ret = vma->vm_ops->access(vma, addr, buf, -- 2.39.2