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gzip: fix for undefined behavior.

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Unportable left shift reported with MKSANITIZER=yes
USE_SANITIZER=undefined:

# progress -zf ./games.tgz  tar -xp -C "./" -f -
/public/src.git/usr.bin/gzip/gzip.c:2126:33: runtime error: left shift of
251 by 24 places cannot be represented in type 'int'
100%
|****************************************************************************************************************|
44500 KiB  119.69 MiB/s    00:00 ETA

Refactor the following code into something that is more clear
and fix signed integer shift, by casting all buf[] elements to
(unsigned int):

unsigned char buf[8];
uint32_t usize;
[...]
else {
    usize = buf[4] | buf[5] << 8 |
            buf[6] << 16 | buf[7] << 24;
[...]

New version:

    usize = buf[4];
    usize |= (unsigned int)buf[5] << 8;
    usize |= (unsigned int)buf[6] << 16;
    usize |= (unsigned int)buf[7] << 24;

Only the "<< 24" part needs explicit cast, but for consistency make the
integer promotion explicit and clear to a code reader.

Sponsored by <The NetBSD Foundation>

Obtained from:	NetBSD (CVS rev. 1.113)
MFC after:	1 week
This commit is contained in:
Pedro F. Giffuni 2018-07-08 22:39:33 +00:00
parent 0592ad0252
commit 3fcbc83d04
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=336113
1 changed files with 9 additions and 5 deletions
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14
usr.bin/gzip/gzip.c
View file

@ -1,4 +1,4 @@
/* $NetBSD: gzip.c,v 1.112 2017/08/23 13:04:17 christos Exp $ */
/* $NetBSD: gzip.c,v 1.113 2018/06/12 00:42:17 kamil Exp $ */
/*-
* SPDX-License-Identifier: BSD-2-Clause-NetBSD
@ -2169,12 +2169,16 @@ print_list(int fd, off_t out, const char *outfile, time_t ts)
maybe_warnx("read of uncompressed size");
else {
usize = buf[4] | buf[5] << 8 |
buf[6] << 16 | buf[7] << 24;
usize = buf[4];
usize |= (unsigned int)buf[5] << 8;
usize |= (unsigned int)buf[6] << 16;
usize |= (unsigned int)buf[7] << 24;
in = (off_t)usize;
#ifndef SMALL
crc = buf[0] | buf[1] << 8 |
buf[2] << 16 | buf[3] << 24;
crc = buf[0];
crc |= (unsigned int)buf[1] << 8;
crc |= (unsigned int)buf[2] << 16;
crc |= (unsigned int)buf[3] << 24;
#endif
}
}