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04:05, Lance Yang wrote: > > From: Lance Yang > > > > The prev pointer was uninitialized, which could lead to undefined behavior > > where its address is taken and passed to the visit() callback without being > > assigned a value. > > So, we are passing the pointer value to visit(), which is not undefined > behavior. > > The issue would be if anybody takes a look at the value stored at that > pointer. Because, already passing an uninitialized value to a (non-inlined) > function is undefined behavior according to C. > > In madvise_update_vma()->vma_modify_flags_name() we do exactly that, > correct? Err the parameter there is struct vm_area_struct **prev... We deref to the prev ptr which is unassigned yes but the pointer to the pointer isn't... > > vma = vma_modify_flags_name(&vmi, *prev, ... > > We should use Fixes: then. So no we shouldn't... > > > Acked-by: David Hildenbrand Sure? :) > > > > > Initializing it to NULL makes the code safer and prevents potential bugs > > if a future callback function attempts to read from it. > > > > Signed-off-by: Lance Yang > > --- > > mm/madvise.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/mm/madvise.c b/mm/madvise.c > > index 267d8e4adf31..c87325000303 100644 > > --- a/mm/madvise.c > > +++ b/mm/madvise.c > > @@ -1536,10 +1536,10 @@ int madvise_walk_vmas(struct mm_struct *mm, unsigned long start, > > struct vm_area_struct **prev, unsigned long start, > > unsigned long end, void *arg)) > > { > > + struct vm_area_struct *prev = NULL; > > struct vm_area_struct *vma; > > - struct vm_area_struct *prev; > > - unsigned long tmp; > > int unmapped_error = 0; > > + unsigned long tmp; > > int error; > > /* > > > -- > Cheers, > > David / dhildenb >