Commit 8351760f authored Apr 05, 2018 by Yury Norov Committed by Linus Torvalds Apr 05, 2018

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/20180404162647.15763-1-ynorov@caviumnetworks.com


Fixes: 0a5ce083 ("lib/bitmap.c: make bitmap_parselist() thread-safe and much faster")
Signed-off-by: Yury Norov <ynorov@caviumnetworks.com>
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reported-by: syzbot <syzbot+6887cbb011c8054e8a3d@syzkaller.appspotmail.com>
Cc: Noam Camus <noamca@mellanox.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 5df63c2a

lib/bitmap.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -607,7 +607,7 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
		/* if no digit is after '-', it's wrong*/
		if (at_start && in_range)
		return -EINVAL;
		if (!(a <= b) \|\| !(used_size <= group_size))
		if (!(a <= b) \|\| group_size == 0 \|\| !(used_size <= group_size))
		return -EINVAL;
		if (b >= nmaskbits)
		return -ERANGE;

lib/test_bitmap.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -255,6 +255,10 @@ static const struct test_bitmap_parselist parselist_tests[] __initconst = {
		{-EINVAL, "-1", NULL, 8, 0},
		{-EINVAL, "-0", NULL, 8, 0},
		{-EINVAL, "10-1", NULL, 8, 0},
		{-EINVAL, "0-31:", NULL, 8, 0},
		{-EINVAL, "0-31:0", NULL, 8, 0},
		{-EINVAL, "0-31:0/0", NULL, 8, 0},
		{-EINVAL, "0-31:1/0", NULL, 8, 0},
		{-EINVAL, "0-31:10/1", NULL, 8, 0},
		};

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