From: Linus Torvalds Date: Thu, 7 Apr 2011 14:35:50 +0000 (-0700) Subject: mm: avoid wrapping vm_pgoff in mremap() X-Git-Tag: v2.6.27.59~43 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=130d82a534d65c3895ab65e6d309c3609890ddfc;p=thirdparty%2Fkernel%2Fstable.git mm: avoid wrapping vm_pgoff in mremap() commit 982134ba62618c2d69fbbbd166d0a11ee3b7e3d8 upstream. The normal mmap paths all avoid creating a mapping where the pgoff inside the mapping could wrap around due to overflow. However, an expanding mremap() can take such a non-wrapping mapping and make it bigger and cause a wrapping condition. Noticed by Robert Swiecki when running a system call fuzzer, where it caused a BUG_ON() due to terminally confusing the vma_prio_tree code. A vma dumping patch by Hugh then pinpointed the crazy wrapped case. Reported-and-tested-by: Robert Swiecki Acked-by: Hugh Dickins Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman [wt: 2.6.27 has this code in do_mremap()] --- diff --git a/mm/mremap.c b/mm/mremap.c index 63782eb8e5a88..a27c00798c262 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -333,10 +333,21 @@ unsigned long do_mremap(unsigned long addr, /* We can't remap across vm area boundaries */ if (old_len > vma->vm_end - addr) goto out; - if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) { - if (new_len > old_len) + + /* Need to be careful about a growing mapping */ + if (new_len > old_len) { + unsigned long pgoff; + + if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)) goto out; + pgoff = (addr - vma->vm_start) >> PAGE_SHIFT; + pgoff += vma->vm_pgoff; + if (pgoff + (new_len >> PAGE_SHIFT) < pgoff) { + ret = -EINVAL; + goto out; + } } + if (vma->vm_flags & VM_LOCKED) { unsigned long locked, lock_limit; locked = mm->locked_vm << PAGE_SHIFT;