Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Yury Norov <ynorov@caviumnetworks.com>
To:     Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc:     Yury Norov <ynorov@caviumnetworks.com>, cgroups@vger.kernel.org,
        linux-kernel@vger.kernel.org, lizefan@huawei.com,
        syzkaller-bugs@googlegroups.com, Noam Camus <noamca@mellanox.com>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        Matthew Wilcox <mawilcox@microsoft.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: [PATCH] lib: fix stall in __bitmap_parselist()
Date:   Wed,  4 Apr 2018 19:26:47 +0300
Message-Id: <20180404162647.15763-1-ynorov@caviumnetworks.com>
MIME-Version: 1.0
Content-Type: text/plain
Received-SPF: None (protection.outlook.com: cavium.com does not designate
 permitted sender hosts)
SpamDiagnosticOutput: 1:99
SpamDiagnosticMetadata: NSPM
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Apr 2018 16:27:00.5304 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: cc6c8eb3-02b7-4874-21f0-08d59a48e518
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 711e4ccf-2e9b-4bcf-a551-4094005b6194
X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR07MB2910
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

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