From: Michel Lespinasse Date: Thu, 14 Mar 2013 23:50:02 +0000 (-0700) Subject: mm/fremap.c: fix possible oops on error path X-Git-Tag: submit/tizen_common/20140905.094502~3315 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=a2362d24764a4e9a3187fc46b14e1d2cd0657700;p=sdk%2Femulator%2Femulator-kernel.git 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 Cc: Tommi Rantala Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/mm/fremap.c b/mm/fremap.c index 6a8da7ee85fd..4723ac8d2fc2 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)