linux-kernel - [PATCH 3/6] lib/bitmap: make bitmap_parse_user a wrapper on bitmap

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Date:   Sat, 27 Apr 2019 20:29:33 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Amritha Nambiar <amritha.nambiar@...el.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Matthew Wilcox <willy@...radead.org>,
        "Tobin C . Harding" <tobin@...nel.org>,
        Will Deacon <will.deacon@....com>,
        Miklos Szeredi <mszeredi@...hat.com>,
        Vineet Gupta <vineet.gupta1@...opsys.com>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Cc:     Yury Norov <ynorov@...vell.com>, linux-kernel@...r.kernel.org,
        Yury Norov <yury.norov@...il.com>,
        Jens Axboe <axboe@...nel.dk>,
        Steffen Klassert <steffen.klassert@...unet.com>
Subject: [PATCH 3/6] lib/bitmap: make bitmap_parse_user a wrapper on bitmap_parse

Currently we parse user data byte after byte which leads to
overcomplicating of parsing algorithm. There are no performance
critical users of bitmap_parse_user(), and so we can duplicate
user data to kernel buffer and simply call bitmap_parselist().
This rework lets us unify and simplify bitmap_parse() and
bitmap_parse_user(), which is done in the following patch.

Signed-off-by: Yury Norov <ynorov@...vell.com>
---
 lib/bitmap.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/lib/bitmap.c b/lib/bitmap.c
index f235434df87b..300732031fad 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -434,22 +434,22 @@ EXPORT_SYMBOL(__bitmap_parse);
  *    then it must be terminated with a \0.
  * @maskp: pointer to bitmap array that will contain result.
  * @nmaskbits: size of bitmap, in bits.
- *
- * Wrapper for __bitmap_parse(), providing it with user buffer.
- *
- * We cannot have this as an inline function in bitmap.h because it needs
- * linux/uaccess.h to get the access_ok() declaration and this causes
- * cyclic dependencies.
  */
 int bitmap_parse_user(const char __user *ubuf,
 			unsigned int ulen, unsigned long *maskp,
 			int nmaskbits)
 {
-	if (!access_ok(ubuf, ulen))
-		return -EFAULT;
-	return __bitmap_parse((const char __force *)ubuf,
-				ulen, 1, maskp, nmaskbits);
+	char *buf;
+	int ret;
 
+	buf = memdup_user_nul(ubuf, ulen);
+	if (IS_ERR(buf))
+		return PTR_ERR(buf);
+
+	ret = bitmap_parse(buf, ulen, maskp, nmaskbits);
+
+	kfree(buf);
+	return ret;
 }
 EXPORT_SYMBOL(bitmap_parse_user);
 
-- 
2.17.1