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Subject[PATCH] lib: fix stall in __bitmap_parselist()
Date
syzbot is catching stalls at __bitmap_parselist() [1]. 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.

Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reported-by: syzbot <syzbot+6887cbb011c8054e8a3d@syzkaller.appspotmail.com>
Signed-off-by: Yury Norov <ynorov@caviumnetworks.com>
---
lib/bitmap.c | 2 +-
lib/test_bitmap.c | 4 ++++
2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/lib/bitmap.c b/lib/bitmap.c
index 9e498c77ed0e..a42eff7e8c48 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -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;
diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
index 756f20ad03db..de16f7869fb1 100644
--- a/lib/test_bitmap.c
+++ b/lib/test_bitmap.c
@@ -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},
};

--
2.14.1
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