Re: gzip memory corruption



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Hi,

Xin LI wrote:
Eygene Ryabinkin wrote:
Wed, Jul 08, 2009 at 10:33:39PM +0300, rrl wrote:
I run Freebsd 7.2 and gzip doesn't handle correctly long suffix name
with the -S option.
gzip -S `perl -e 'print "A"x1200'` dummy_file
Memory fault (core dumped)

The offending code lays in the function file_compress:
/* Add (usually) .gz to filename */
if ((size_t)snprintf(outfile, outsize, "%s%s",
file, suffixes[0].zipped) >= outsize)
memcpy(outfile - suffixes[0].ziplen - 1,
suffixes[0].zipped, suffixes[0].ziplen + 1);
The memcpy() call looks like a complete madness: it will write before
the beginning of the 'outfile', so it will be buffer underflow in any
case (unless I am terribly mistaken and missing some obvious point).

I'd change the above code to warn and return if snprintf will discard
some trailing characters, the patch is attached.

I have attached another possible fix, which catches the problem when
parsing the command line. The point is that, I think we really want to
catch bad input as early as possible.

If there is no objections I would request for approval from re@.

Cheers,
- --
Xin LI <delphij@xxxxxxxxxxx> http://www.delphij.net/
FreeBSD - The Power to Serve!
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Index: gzip.c
===================================================================
--- gzip.c (ç??æ?¬ 195435)
+++ gzip.c (工���)
@@ -372,6 +372,8 @@
case 'S':
len = strlen(optarg);
if (len != 0) {
+ if (len >= PATH_MAX)
+ errx(1, "incorrect suffix: '%s'", optarg);
suffixes[0].zipped = optarg;
suffixes[0].ziplen = len;
} else {
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