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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Yury Norov <ynorov@caviumnetworks.com>,
        Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
        syzbot <syzbot+6887cbb011c8054e8a3d@syzkaller.appspotmail.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>,
        Linus Torvalds <torvalds@linux-foundation.org>
Subject: [PATCH 4.15 30/53] lib: fix stall in __bitmap_parselist()
Date:   Tue, 17 Apr 2018 17:58:55 +0200
Message-Id: <20180417155724.623157623@linuxfoundation.org>
In-Reply-To: <20180417155723.091120060@linuxfoundation.org>
References: <20180417155723.091120060@linuxfoundation.org>
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4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Yury Norov <ynorov@caviumnetworks.com>

commit 8351760ff5b2042039554b4948ddabaac644a976 upstream.

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: 0a5ce0831d04382a ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 lib/bitmap.c      |    2 +-
 lib/test_bitmap.c |    4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -607,7 +607,7 @@ static int __bitmap_parselist(const char
 		/* 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;
--- a/lib/test_bitmap.c
+++ b/lib/test_bitmap.c
@@ -218,6 +218,10 @@ static const struct test_bitmap_parselis
 	{-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},
 };