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| author | Michel Lespinasse <walken@google.com> | 2013-03-14 23:50:02 (GMT) |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-03-15 00:00:39 (GMT) |
| commit | a2362d24764a4e9a3187fc46b14e1d2cd0657700 (patch) | |
| tree | b4b067886ae9a6f7cc8bff96ab2f7096b1f493aa | |
| parent | f4846e52c51755fe1dd6642a117bc23cd0655c95 (diff) | |
| download | linux-a2362d24764a4e9a3187fc46b14e1d2cd0657700.tar.xz | |
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>
| -rw-r--r-- | mm/fremap.c | 5 |
1 files changed, 2 insertions, 3 deletions
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 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size, 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 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size, * 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) |