1295371 - freetype2: left shift of negative value in [@tt_sbit_decoder_load_bit_aligned]

Status: RESOLVED FIXED

(Core :: Graphics: Text, defect)

Description

[Tyson Smith [:tsmith]]

Attachment: test_case.ttf

Found while fuzzing freetype2 commit 248f5629d8889aa5b77ea5bfce0935140293d50d (>2.6.5)

I'm not sure if this affects the browser or if we are protected by OTS. I'm also not sure how far this bug goes back.

src/sfnt/ttsbit.c:867:39: runtime error: left shift of negative value -4081
    #0 0x7fe197e03163 in tt_sbit_decoder_load_bit_aligned src/sfnt/ttsbit.c:877:29
    #1 0x7fe197dfde04 in tt_sbit_decoder_load_bitmap src/sfnt/ttsbit.c:1162:15
    #2 0x7fe197dfde04 in tt_sbit_decoder_load_image src/sfnt/ttsbit.c:1357
    #3 0x7fe197e0392b in tt_sbit_decoder_load_compound src/sfnt/ttsbit.c:949:15
    #4 0x7fe197dfde04 in tt_sbit_decoder_load_bitmap src/sfnt/ttsbit.c:1162:15
    #5 0x7fe197dfde04 in tt_sbit_decoder_load_image src/sfnt/ttsbit.c:1357
    #6 0x7fe197dec52a in tt_face_load_sbit_image src/sfnt/ttsbit.c:1523:19
    #7 0x7fe197bd08e4 in load_sbit_image src/truetype/ttgload.c:2189:13
    #8 0x7fe197bd08e4 in TT_Load_Glyph src/truetype/ttgload.c:2608
    #9 0x7fe197bd08e4 in tt_glyph_load src/truetype/ttdriver.c:424
    #10 0x7fe197b2233e in FT_Load_Glyph src/base/ftobjs.c:742:15
    #11 0x4ea5aa in TestFace src/tools/ftrandom/../../../src/tools/ftrandom/ftrandom.c:105:12
    #12 0x4ea5aa in ExecuteTest src/tools/ftrandom/../../../src/tools/ftrandom/ftrandom.c:143
    #13 0x4ea5aa in main src/tools/ftrandom/../../../src/tools/ftrandom/ftrandom.c:166
    #14 0x7fe196be982f in __libc_start_main /build/glibc-GKVZIf/glibc-2.23/csu/../csu/libc-start.c:291
    #15 0x418a78 in _start (/home/user/workspace/freetype2/ftrandom+0x418a78)

Comment 1

[Werner Lemberg]

Sorry, can't repeat.  Please provide the failing `test_case.ttf` instance.

Comment 2

[Tyson Smith [:tsmith]]

I can repro with the attached test_case.ttf with the latest revision from git. FWIW I am using the same ftrandom.c file as bug 1272173.

I am using the using the following build args:
CC=clang CFLAGS="-fsanitize=undefined -fno-sanitize-recover=undefined -g -O2" LDFLAGS=-fsanitize=undefined

I hope this helps, if not I can try finding a different test case.

Comment 3

[Tyson Smith [:tsmith]]

Logged as: https://savannah.nongnu.org/bugs/?48980

Comment 4

[Tyson Smith [:tsmith]]

Fixed in FreeType 2.7