On Sat, Dec 19, 2020 at 05:04:33PM +0000, Kalesh Singh wrote: > When `next < old_addr`, `next - old_addr` arithmetic underflows > causing `extent` to be incorrect. > > Make `extent` the smaller of `next - old_addr` or `old_end - old_addr`. > > Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx> > Signed-off-by: Kalesh Singh <kaleshsingh@xxxxxxxxxx> This patch fixes the problem I had observed when booting 'parisc' images. Tested-by: Guenter Roeck <linux@xxxxxxxxxxxx> Guenter > --- > mm/mremap.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/mm/mremap.c b/mm/mremap.c > index c5590afe7165..f554320281cc 100644 > --- a/mm/mremap.c > +++ b/mm/mremap.c > @@ -358,7 +358,9 @@ static unsigned long get_extent(enum pgt_entry entry, unsigned long old_addr, > > next = (old_addr + size) & mask; > /* even if next overflowed, extent below will be ok */ > - extent = (next > old_end) ? old_end - old_addr : next - old_addr; > + extent = next - old_addr; > + if (extent > old_end - old_addr) > + extent = old_end - old_addr; > next = (new_addr + size) & mask; > if (extent > next - new_addr) > extent = next - new_addr; > -- > 2.29.2.729.g45daf8777d-goog >
