lib: fix stall in __bitmap_parselist()

syzbot is catching stalls at __bitmap_parselist()
(https://syzkaller.appspot.com/bug?id=ad7e0351fbc90535558514a71cd3edc11681997a).
The trigger is

  unsigned long v = 0;
  bitmap_parselist("7:,", &v, BITS_PER_LONG);

which results in hitting infinite loop at

    while (a <= b) {
	    off = min(b - a + 1, used_size);
	    bitmap_set(maskp, a, off);
	    a += group_size;
    }

due to used_size == group_size == 0.

Link: http://lkml.kernel.org/r/[email protected]
Fixes: 0a5ce0831d04382a ("lib/bitmap.c: make bitmap_parselist() thread-safe and much faster")
Signed-off-by: Yury Norov <[email protected]>
Reported-by: Tetsuo Handa <[email protected]>
Reported-by: syzbot <[email protected]>
Cc: Noam Camus <[email protected]>
Cc: Rasmus Villemoes <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Mauro Carvalho Chehab <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions