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authorLinus Torvalds <torvalds@linux-foundation.org>2009-01-29 17:46:42 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2009-01-29 17:46:42 -0800
commitde33c8db5910cda599899dd431cc30d7c1018cbf (patch)
tree4ee9ba8685bae5d1719a3158284d0c197c83afde /mm
parent18e352e4a73465349711a9324767e1b2453383e2 (diff)
downloadlinux-de33c8db5910cda599899dd431cc30d7c1018cbf.tar.gz
Fix OOPS in mmap_region() when merging adjacent VM_LOCKED file segments
As of commit ba470de43188cdbff795b5da43a1474523c6c2fb ("map: handle mlocked pages during map, remap, unmap") we now use the 'vma' variable at the end of mmap_region() to handle the page-in of newly mapped mlocked pages. However, if we merged adjacent vma's together, the vma we're using may be stale. We historically consciously avoided using it after the merge operation, but that got overlooked when redoing the locked page handling. This commit simplifies mmap_region() by doing any vma merges early, avoiding the issue entirely, and 'vma' will always be valid. As pointed out by Hugh Dickins, this depends on any drivers that change the page offset of flags to have set one of the VM_SPECIAL bits (so that they cannot trigger the early merge logic), but that's true in general. Reported-and-tested-by: Maksim Yevmenkin <maksim.yevmenkin@gmail.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com> Cc: Nick Piggin <npiggin@suse.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Hugh Dickins <hugh@veritas.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/mmap.c26
1 files changed, 6 insertions, 20 deletions
diff --git a/mm/mmap.c b/mm/mmap.c
index 8d95902e9a3..d3fa10a726c 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1134,16 +1134,11 @@ munmap_back:
}
/*
- * Can we just expand an old private anonymous mapping?
- * The VM_SHARED test is necessary because shmem_zero_setup
- * will create the file object for a shared anonymous map below.
+ * Can we just expand an old mapping?
*/
- if (!file && !(vm_flags & VM_SHARED)) {
- vma = vma_merge(mm, prev, addr, addr + len, vm_flags,
- NULL, NULL, pgoff, NULL);
- if (vma)
- goto out;
- }
+ vma = vma_merge(mm, prev, addr, addr + len, vm_flags, NULL, file, pgoff, NULL);
+ if (vma)
+ goto out;
/*
* Determine the object being mapped and call the appropriate
@@ -1206,17 +1201,8 @@ munmap_back:
if (vma_wants_writenotify(vma))
vma->vm_page_prot = vm_get_page_prot(vm_flags & ~VM_SHARED);
- if (file && vma_merge(mm, prev, addr, vma->vm_end,
- vma->vm_flags, NULL, file, pgoff, vma_policy(vma))) {
- mpol_put(vma_policy(vma));
- kmem_cache_free(vm_area_cachep, vma);
- fput(file);
- if (vm_flags & VM_EXECUTABLE)
- removed_exe_file_vma(mm);
- } else {
- vma_link(mm, vma, prev, rb_link, rb_parent);
- file = vma->vm_file;
- }
+ vma_link(mm, vma, prev, rb_link, rb_parent);
+ file = vma->vm_file;
/* Once vma denies write, undo our temporary denial count */
if (correct_wcount)