Heap overflow in get_charset in ftbench.c
face->num_glyphs can be zero, as a result, first_index and last_index would be -1. Those variables will be used in get_charset function.
1244
1245 if ( first_index >= face->num_glyphs )
1246 first_index = face->num_glyphs - 1;
► 1247 if ( last_index >= face->num_glyphs )
1248 last_index = face->num_glyphs - 1;
1249 incr_index = last_index > first_index ? 1 : -1;
1250In get_charset, variable i would be assigned -1 and this code would access charset->code[-1] resulting out-of-bound access.
#define FOREACH( i ) for ( i = first_index ; \
( first_index <= i && i <= last_index ) || \
( first_index >= i && i >= last_index ) ; \
i += incr_index )
void get_charset(){
...
{
int j;
/* no charmap, do an identity mapping */
FOREACH( j )
charset->code[i++] = (FT_ULong)j;
}
...
stack trace:
=================================================================
==2736368==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x602000000130 at pc 0x00000050005f bp 0x7fff84c241b0 sp 0x7fff84c241a8
WRITE of size 8 at 0x602000000130 thread T0
#0 0x50005e in get_charset /targets/struct/freetype/dbg/freetype-demos/src/ftbench.c:820:28
#1 0x4fcc28 in main /targets/struct/freetype/dbg/freetype-demos/src/ftbench.c:1420:11
#2 0x7fb18708b0b2 in __libc_start_main /build/glibc-sMfBJT/glibc-2.31/csu/../csu/libc-start.c:308:16
#3 0x41f6bd in _start (/targets/struct/freetype/dbg/fuzzrun/ftbench+0x41f6bd)
0x602000000131 is located 0 bytes to the right of 1-byte region [0x602000000130,0x602000000131)
allocated by thread T0 here:
#0 0x4c4987 in calloc /fuzz/fuzzdeps/llvm-project-11.0.0/compiler-rt/lib/asan/asan_malloc_linux.cpp:154:3
#1 0x4ffc36 in get_charset /targets/struct/freetype/dbg/freetype-demos/src/ftbench.c:787:32
#2 0x4fcc28 in main /targets/struct/freetype/dbg/freetype-demos/src/ftbench.c:1420:11
#3 0x7fb18708b0b2 in __libc_start_main /build/glibc-sMfBJT/glibc-2.31/csu/../csu/libc-start.c:308:16
SUMMARY: AddressSanitizer: heap-buffer-overflow /targets/struct/freetype/dbg/freetype-demos/src/ftbench.c:820:28 in get_charset
Shadow bytes around the buggy address:
0x0c047fff7fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c047fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c047fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0c047fff8000: fa fa 04 fa fa fa 00 fa fa fa 00 fa fa fa 00 fa
0x0c047fff8010: fa fa 00 fa fa fa 00 fa fa fa fd fa fa fa fd fa
=>0x0c047fff8020: fa fa fd fa fa fa[01]fa fa fa fa fa fa fa fa fa
0x0c047fff8030: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff8040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff8050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff8060: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff8070: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
Container overflow: fc
Array cookie: ac
Intra object redzone: bb
ASan internal: fe
Left alloca redzone: ca
Right alloca redzone: cb
Shadow gap: cc
==2736368==ABORTING
[1] 2736368 abort ./ftbench -c 1reproduce steps:
ftbench -c 1 ./poc