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commitf4e9e0e694upstream. set_mempolicy_home_node() iterates over a list of VMAs and calls mbind_range() on each VMA, which also iterates over the singular list of the VMA passed in and potentially splits the VMA. Since the VMA iterator is not passed through, set_mempolicy_home_node() may now point to a stale node in the VMA tree. This can result in a UAF as reported by syzbot. Avoid the stale maple tree node by passing the VMA iterator through to the underlying call to split_vma(). mbind_range() is also overly complicated, since there are two calling functions and one already handles iterating over the VMAs. Simplify mbind_range() to only handle merging and splitting of the VMAs. Align the new loop in do_mbind() and existing loop in set_mempolicy_home_node() to use the reduced mbind_range() function. This allows for a single location of the range calculation and avoids constantly looking up the previous VMA (since this is a loop over the VMAs). Link: https://lore.kernel.org/linux-mm/000000000000c93feb05f87e24ad@google.com/ Fixes:66850be55e("mm/mempolicy: use vma iterator & maple state instead of vma linked list") Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com> Reported-by: syzbot+a7c1ec5b1d71ceaa5186@syzkaller.appspotmail.com Link: https://lkml.kernel.org/r/20230410152205.2294819-1-Liam.Howlett@oracle.com Tested-by: syzbot+a7c1ec5b1d71ceaa5186@syzkaller.appspotmail.com Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>