Segmentation fault (ASAN: SEGV on unknown address) in the load_pnm function of frompnm.c:288

[gutiniao]

A crafted input will lead to crash in frompnm.c at libsixel 1.8.2.

Triggered by:
./img2sixel 004-SEGV-load-pnm288

Poc:
004-SEGV-load-pnm288

The gdb debug info:

# gdb ./img2sixel 
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Reading symbols from ./img2sixel...done.
(gdb) r 004-SEGV-load-pnm288
Starting program: /usr/local/libsixel-fuzz/bin/img2sixel 004-SEGV-load-pnm288

Program received signal SIGSEGV, Segmentation fault.
load_pnm (p=0x55555575b39c "", length=<optimized out>, allocator=<optimized out>, result=<optimized out>, psx=0x5555557635d8, psy=0x5555557635dc, ppalette=0x5555557635d0, pncolors=0x5555557635e0, ppixelformat=0x5555557635e4) at frompnm.c:288
288	            *(*result + (y * width + x) * 3 + 0) = component[0];
(gdb) l
283	                break;
284	            default:
285	                goto unknown;
286	            }
287	
288	            *(*result + (y * width + x) * 3 + 0) = component[0];
289	            *(*result + (y * width + x) * 3 + 1) = component[1];
290	            *(*result + (y * width + x) * 3 + 2) = component[2];
291	        }
292	    }
(gdb) bt
#0  load_pnm (p=0x55555575b39c "", length=<optimized out>, allocator=<optimized out>, result=<optimized out>, psx=0x5555557635d8, psy=0x5555557635dc, ppalette=0x5555557635d0, pncolors=0x5555557635e0, ppixelformat=0x5555557635e4) at frompnm.c:288
#1  0x00007ffff7b799e0 in load_with_builtin (pchunk=0x55555575b350, fstatic=fstatic@entry=0, fuse_palette=fuse_palette@entry=1, reqcolors=reqcolors@entry=256, bgcolor=bgcolor@entry=0x0, loop_control=<optimized out>, fn_load=0x7ffff7b96de0 <load_image_callback>, 
    context=0x55555575b290) at loader.c:801
#2  0x00007ffff7b835cb in sixel_helper_load_image_file (filename=filename@entry=0x7fffffffe806 "004-SEGV-load-pnm289", fstatic=0, fuse_palette=fuse_palette@entry=1, reqcolors=256, bgcolor=0x0, loop_control=0, fn_load=0x7ffff7b96de0 <load_image_callback>, finsecure=0, 
    cancel_flag=0x55555575a050 <signaled>, context=0x55555575b290, allocator=0x55555575b260) at loader.c:1352
#3  0x00007ffff7b9d42c in sixel_encoder_encode (encoder=0x55555575b290, filename=0x7fffffffe806 "004-SEGV-load-pnm289") at encoder.c:1737
#4  0x0000555555555af6 in main (argc=2, argv=0x7fffffffe598) at img2sixel.c:457
(gdb)

[saitoha]

This problem is not reproduced on v1.8.3 because it is fixed by e17c076. Thanks!

[carnil]

CVE-2019-20022 has been assigned for this issue.