A heap-buffer-overflow in slaxlexer.c:751:13

[seviezhou]

System info

Ubuntu X64, gcc (Ubuntu 5.5.0-12ubuntu1), slaxproc (latest master 45d88a)

Configure

CFLAGS="-g -fsanitize=address" LDFLAGS="-fsanitize=address" ./configure

Command line

./build/slaxproc/slaxproc -o /dev/null -x @@

AddressSanitizer output

=================================================================
==59937==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x625000002100 at pc 0x0000005671b1 bp 0x7fff6c8e6110 sp 0x7fff6c8e6108
READ of size 1 at 0x625000002100 thread T0
    #0 0x5671b0 in slaxIsCommentStart /home/seviezhou/libslax/build/libslax/../../libslax/slaxlexer.c:751:13
    #1 0x5671b0 in slaxLexer /home/seviezhou/libslax/build/libslax/../../libslax/slaxlexer.c:919
    #2 0x55f3a5 in slaxYylex /home/seviezhou/libslax/build/libslax/../../libslax/slaxlexer.c:1272:10
    #3 0x579c59 in slaxParse /home/seviezhou/libslax/build/libslax/slaxparser.c:2447:16
    #4 0x56df6e in slaxLoadFile /home/seviezhou/libslax/build/libslax/../../libslax/slaxloader.c:731:10
    #5 0x524b1e in do_slax_to_xslt /home/seviezhou/libslax/build/slaxproc/../../slaxproc/slaxproc.c:156:9
    #6 0x51f1d8 in main /home/seviezhou/libslax/build/slaxproc/../../slaxproc/slaxproc.c:1039:5
    #7 0x7efccb60f83f in __libc_start_main /build/glibc-e6zv40/glibc-2.23/csu/../csu/libc-start.c:291
    #8 0x41d818 in _start (/home/seviezhou/libslax/build/slaxproc/slaxproc+0x41d818)

0x625000002100 is located 0 bytes to the right of 8192-byte region [0x625000000100,0x625000002100)
allocated by thread T0 here:
    #0 0x4e1e90 in realloc /home/seviezhou/llvm-6.0.0/projects/compiler-rt/lib/asan/asan_malloc_linux.cc:107
    #1 0x55daf3 in slaxGetInput /home/seviezhou/libslax/build/libslax/../../libslax/slaxlexer.c:601:14

SUMMARY: AddressSanitizer: heap-buffer-overflow /home/seviezhou/libslax/build/libslax/../../libslax/slaxlexer.c:751:13 in slaxIsCommentStart
Shadow bytes around the buggy address:
  0x0c4a7fff83d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c4a7fff83e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c4a7fff83f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c4a7fff8400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c4a7fff8410: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c4a7fff8420:[fa]fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c4a7fff8430: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c4a7fff8440: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c4a7fff8450: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c4a7fff8460: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c4a7fff8470: 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
==59937==ABORTING

POC

heap-overflow-slaxIsCommentStart-slaxlexer-751.zip