From e37b620fe8f14535d737e89a4dcabaed4517bf1a Mon Sep 17 00:00:00 2001 From: Tim Kientzle Date: Sun, 21 Aug 2016 10:51:43 -0700 Subject: [PATCH] Issue #767: Buffer overflow printing a filename The safe_fprintf function attempts to ensure clean output for an arbitrary sequence of bytes by doing a trial conversion of the multibyte characters to wide characters -- if the resulting wide character is printable then we pass through the corresponding bytes unaltered, otherwise, we convert them to C-style ASCII escapes. The stack trace in Issue #767 suggest that the 20-byte buffer was getting overflowed trying to format a non-printable multibyte character. This should only happen if there is a valid multibyte character of more than 5 bytes that was unprintable. (Each byte would get expanded to a four-charcter octal-style escape of the form "\123" resulting in >20 characters for the >5 byte multibyte character.) I've not been able to reproduce this, but have expanded the conversion buffer to 128 bytes on the belief that no multibyte character set has a single character of more than 32 bytes. --- tar/util.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tar/util.c b/tar/util.c index 9ff22f2..2b4aebe 100644 --- a/tar/util.c +++ b/tar/util.c @@ -182,7 +182,7 @@ safe_fprintf(FILE *f, const char *fmt, ...) } /* If our output buffer is full, dump it and keep going. */ - if (i > (sizeof(outbuff) - 20)) { + if (i > (sizeof(outbuff) - 128)) { outbuff[i] = '\0'; fprintf(f, "%s", outbuff); i = 0;