mm/fremap.c: fix possible oops on error path
The vm_flags introduced in 6d7825b10dbe ("mm/fremap.c: fix oops on error
path") is supposed to avoid a compiler warning about unitialized
vm_flags without changing the generated code.
However I am concerned that this is going to be very brittle, and fail
with some compiler versions. The failure could be either of:
- compiler could actually load vma->vm_flags before checking for the
!vma condition, thus reintroducing the oops
- compiler could optimize out the !vma check, since the pointer just got
dereferenced shortly before (so the compiler knows it can't be NULL!)
I propose reversing this part of the change and initializing vm_flags to 0
just to avoid the bogus uninitialized use warning.
Signed-off-by: Michel Lespinasse <walken@google.com>
Cc: Tommi Rantala <tt.rantala@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/fremap.c b/mm/fremap.c
index 6a8da7e..4723ac8 100644
--- a/mm/fremap.c
+++ b/mm/fremap.c
@@ -129,7 +129,7 @@
struct vm_area_struct *vma;
int err = -EINVAL;
int has_write_lock = 0;
- vm_flags_t vm_flags;
+ vm_flags_t vm_flags = 0;
if (prot)
return err;
@@ -163,8 +163,7 @@
* and that the remapped range is valid and fully within
* the single existing vma.
*/
- vm_flags = vma->vm_flags;
- if (!vma || !(vm_flags & VM_SHARED))
+ if (!vma || !(vma->vm_flags & VM_SHARED))
goto out;
if (!vma->vm_ops || !vma->vm_ops->remap_pages)