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From: Alexey Dobriyan <adobriyan@gmail.com>
To: akpm@linux-foundation.org
Cc: linux-kernel@vger.kernel.org
Subject: [PATCH 04/10] sscanf: fix overflow
Date: Sat, 2 May 2015 03:51:16 +0300	[thread overview]
Message-ID: <20150502005116.GD21655@p183.telecom.by> (raw)
In-Reply-To: <20150502004714.GA21655@p183.telecom.by>

Fun fact:

	uint8_t val;
	sscanf("256", "%hhu", &val);

will return 1 (as it should), and make val=0 (as it should not).

Apart from correctness, patch allows to remove checks and switch
to proper types in several (most?) cases:

	grep -e 'scanf.*%[0-9]\+[dioux]' -n -r .

Such checks can be incorrect too, checking for 3 digits with %3u
for parsing uint8_t is not enough.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

 lib/vsprintf.c |   45 ++++++++++++++++++++++++++++++++++-----------
 1 file changed, 34 insertions(+), 11 deletions(-)

--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -2632,44 +2632,67 @@ int vsscanf(const char *buf, const char *fmt, va_list args)
 
 		switch (qualifier) {
 		case 'H':	/* that's 'hh' in format */
-			if (is_sign)
+			if (is_sign) {
+				if (val.s != (signed char)val.s)
+					goto out;
 				*va_arg(args, signed char *) = val.s;
-			else
+			} else {
+				if (val.u != (unsigned char)val.u)
+					goto out;
 				*va_arg(args, unsigned char *) = val.u;
+			}
 			break;
 		case 'h':
-			if (is_sign)
+			if (is_sign) {
+				if (val.s != (short)val.s)
+					goto out;
 				*va_arg(args, short *) = val.s;
-			else
+			} else {
+				if (val.u != (unsigned short)val.u)
+					goto out;
 				*va_arg(args, unsigned short *) = val.u;
+			}
 			break;
 		case 'l':
-			if (is_sign)
+			if (is_sign) {
+				if (val.s != (long)val.s)
+					goto out;
 				*va_arg(args, long *) = val.s;
-			else
+			} else {
+				if (val.u != (unsigned long)val.u)
+					goto out;
 				*va_arg(args, unsigned long *) = val.u;
+			}
 			break;
 		case 'L':
-			if (is_sign)
+			if (is_sign) {
 				*va_arg(args, long long *) = val.s;
-			else
+			} else {
 				*va_arg(args, unsigned long long *) = val.u;
+			}
 			break;
 		case 'Z':
 		case 'z':
+			if (val.u != (size_t)val.u)
+				goto out;
 			*va_arg(args, size_t *) = val.u;
 			break;
 		default:
-			if (is_sign)
+			if (is_sign) {
+				if (val.s != (int)val.s)
+					goto out;
 				*va_arg(args, int *) = val.s;
-			else
+			} else {
+				if (val.u != (unsigned int)val.u)
+					goto out;
 				*va_arg(args, unsigned int *) = val.u;
+			}
 			break;
 		}
 		num++;
 		str += len;
 	}
-
+out:
 	return num;
 }
 EXPORT_SYMBOL(vsscanf);

  parent reply	other threads:[~2015-05-02  0:51 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-05-02  0:47 [PATCH 01/10] Add parse_integer() (replacement for simple_strto*()) Alexey Dobriyan
2015-05-02  0:48 ` [PATCH 02/10] parse_integer: rewrite kstrto*() Alexey Dobriyan
2015-05-02  0:50 ` [PATCH 03/10] parse_integer: convert sscanf() Alexey Dobriyan
2015-05-02  1:10   ` [PATCH CORRECT " Alexey Dobriyan
2015-05-02  0:51 ` Alexey Dobriyan [this message]
2015-05-05  9:51   ` [PATCH 04/10] sscanf: fix overflow Rasmus Villemoes
2015-05-05 11:10     ` Alexey Dobriyan
2015-05-06  7:49       ` Rasmus Villemoes
2015-05-02  0:53 ` [PATCH 05/10] parse_integer: convert lib/ Alexey Dobriyan
2015-05-04 14:10   ` Rasmus Villemoes
2015-05-04 14:57     ` Alexey Dobriyan
2015-05-02  0:55 ` [PATCH 06/10] parse_integer: convert mm/ Alexey Dobriyan
2015-05-04 14:33   ` Rasmus Villemoes
2015-05-04 15:09     ` Alexey Dobriyan
2015-05-02  0:56 ` [PATCH 07/10] parse_integer: convert misc fs/ code Alexey Dobriyan
2015-05-02  0:59 ` [PATCH 08/10] fs/cachefiles/: convert to parse_integer() Alexey Dobriyan
2015-05-02  1:01 ` [PATCH 09/10] ocfs2: convert to parse_integer()/kstrto*() Alexey Dobriyan
2015-05-02  1:03 ` [PATCH 10/10] ext2, ext3, ext4: " Alexey Dobriyan
2015-05-04 13:24 ` [PATCH 01/10] Add parse_integer() (replacement for simple_strto*()) Rasmus Villemoes
2015-05-04 14:32   ` Alexey Dobriyan
2015-05-04 16:44     ` Rasmus Villemoes
2015-05-04 19:54       ` Alexey Dobriyan
2015-05-04 21:48         ` Rasmus Villemoes

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