shithub: riscv

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ref: 796e7b84bd7a49b97d3e592b4b7537c4ed096457
parent: a74542613df2305bd2fde7485e55fce4fafee0e6
author: cinap_lenrek <cinap_lenrek@felloff.net>
date: Tue Apr 5 07:24:07 EDT 2016

libdraw: fix out of bounds memory access after subfont array reallocation (thanks ray)

/n/bugs/open/libdrawfont.c_buffer_overflow
http://bugs.9front.org/open/libdrawfont.c_buffer_overflow/readme

ray@raylai.com

Hi all,

In plan9port this bug keeps crashing mc when I run lc in a directory with Chinese characters. This is a diff from OpenBSD but it should apply cleanly to the various plan9 sources.

The code is basically trying to do a realloc (I guess realloc wasn't available back then?) but it copies too much from the original buffer.

Since realloc is available, just use it. If realloc isn't available outside plan9port (I haven't checked) the memmove line should be changed from:
	memmove(f->subf, of, (f->nsubf+DSUBF)*sizeof *subf);
to:
	memmove(f->subf, of, f->nsubf*sizeof *subf);

I hope this is helpful.

Ray

--- a/sys/src/libdraw/font.c

+++ b/sys/src/libdraw/font.c

@@ -216,16 +216,14 @@

 			subf->age = 0;

 		}else{				/* too recent; grow instead */

 			of = f->subf;

-			f->subf = malloc((f->nsubf+DSUBF)*sizeof *subf);

+			f->subf = realloc(of, (f->nsubf+DSUBF)*sizeof *subf);

 			if(f->subf == nil){

 				f->subf = of;

 				goto Toss;

 			}

-			memmove(f->subf, of, (f->nsubf+DSUBF)*sizeof *subf);

-			memset(f->subf+f->nsubf, 0, DSUBF*sizeof *subf);

 			subf = &f->subf[f->nsubf];

+			memset(subf, 0, DSUBF*sizeof *subf);

 			f->nsubf += DSUBF;

-			free(of);

 		}

 	}

 	subf->age = 0;