linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Alexey Dobriyan <adobriyan@gmail.com>
To: akpm@linux-foundation.org
Cc: linux-kernel@vger.kernel.org, linux@rasmusvillemoes.dk
Subject: [PATCH 06/12] scanf: fix type range overflow
Date: Fri, 8 May 2015 21:34:32 +0300	[thread overview]
Message-ID: <20150508183432.GD9182@p183.telecom.by> (raw)
In-Reply-To: <20150508182911.GA9044@p183.telecom.by>

Fun fact:

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

will return 1 and make val=0 (clearly bogus).

Userspace sscanf() reports 1 parsed value, returns incorrect value
but sets errno to ERANGE only for "%u" conversion and higher.
%hhu and %hu are left in the cold.

Having no way to report errno=ERANGE in kernel, don't report
successful parsing.

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(-)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 6509c54..58051b4 100644
--- 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);
-- 
2.0.4


  parent reply	other threads:[~2015-05-08 18:34 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-05-08 18:29 [PATCH 01/12] kstrto*: accept "-0" for signed conversion Alexey Dobriyan
2015-05-08 18:30 ` [PATCH 02/12] Add parse_integer() (replacement for simple_strto*()) Alexey Dobriyan
2015-05-08 20:46   ` Andrew Morton
2015-05-08 21:52     ` Rasmus Villemoes
2015-05-10 13:52     ` Alexey Dobriyan
2015-05-13 12:19       ` Alexey Dobriyan
2015-05-10 15:52   ` Noel Grandin
2015-07-09 19:28   ` Andrew Morton
2015-07-10  6:46     ` Alexey Dobriyan
2015-05-08 18:31 ` [PATCH 03/12] parse_integer: add runtime testsuite Alexey Dobriyan
2015-05-08 18:33 ` [PATCH 04/12] parse-integer: rewrite kstrto*() Alexey Dobriyan
2015-05-08 18:33 ` [PATCH 05/12] parse_integer: convert scanf() Alexey Dobriyan
2015-05-08 18:34 ` Alexey Dobriyan [this message]
2015-05-08 18:35 ` [PATCH 07/12] parse_integer: convert lib/ Alexey Dobriyan
2015-05-08 18:35 ` [PATCH 08/12] parse_integer: convert mm/ Alexey Dobriyan
2015-05-08 18:36 ` [PATCH 09/12] parse_integer: convert fs/ Alexey Dobriyan
2015-05-08 18:37 ` [PATCH 10/37] parse_integer: convert fs/cachefiles/ Alexey Dobriyan
2015-05-08 18:39 ` [PATCH 11/12] parse_integer: convert ext2, ext3, ext4 Alexey Dobriyan
2015-05-08 18:40 ` [PATCH 12/12] parse_integer: convert fs/ocfs2/ Alexey Dobriyan

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20150508183432.GD9182@p183.telecom.by \
    --to=adobriyan@gmail.com \
    --cc=akpm@linux-foundation.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux@rasmusvillemoes.dk \
    --subject='Re: [PATCH 06/12] scanf: fix type range overflow' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
on how to clone and mirror all data and code used for this inbox