lkml.org 
[lkml]   [2020]   [Nov]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] lib: vsprintf: Avoid 32-bit truncation in vsscanf number parsing
Date
Number conversion in vsscanf converts a whole string of digits and then
extracts the field width part from the converted value. The maximum run
of digits is limited by overflow. Conversion was using either
simple_strto[u]l or simple_strto[u]ll based on the 'L' qualifier. This
created a difference in truncation between builds where long is 32-bit
and builds where it is 64-bit. This especially affects parsing a run of
contiguous digits into separate fields - the maximum length of the run
is 16 digits if long is 64-bit but only 8 digits if long is 32-bits.
For example a conversion "%6x%6x" would convert both fields correctly if
long is 64-bit but not if long is 32-bit.

It is undesirable for vsscanf to parse numbers differently depending on
the size of long on the target build.

As simple_strto[u]l just calls simple_strto[u]ll anyway the conversion
is always 64-bit, and the result is manipulated as a u64, so this is an
avoidable behaviour difference between 32-bit and 64-bit builds. The
conversion can call simple_strto[u]ll directly and preserve the full
64-bits that were parsed out of the string.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
---
lib/vsprintf.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 14c9a6af1b23..63b6cddfa7f7 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -3444,13 +3444,9 @@ int vsscanf(const char *buf, const char *fmt, va_list args)
break;

if (is_sign)
- val.s = qualifier != 'L' ?
- simple_strtol(str, &next, base) :
- simple_strtoll(str, &next, base);
+ val.s = simple_strtoll(str, &next, base);
else
- val.u = qualifier != 'L' ?
- simple_strtoul(str, &next, base) :
- simple_strtoull(str, &next, base);
+ val.u = simple_strtoull(str, &next, base);

if (field_width > 0 && next - str > field_width) {
if (base == 0)
--
2.20.1
\
 
 \ /
  Last update: 2020-11-12 12:19    [W:0.067 / U:0.528 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site