lrzip: NULL pointer dereference in join_pthread (stream.c)

["Agostino Sarubbo" <ago () gentoo org>]

Description:
lrzip is a compression utility that excels at compressing large files.

The complete ASan output of the issue:

# lrzip -t $FILE
==1329==ERROR: AddressSanitizer: SEGV on unknown address 0x0000000002d0 (pc 0x7fa931ad7660 bp 0x7ffff4a30c30 sp 
0x7ffff4a309f8 T0)
==1329==The signal is caused by a READ memory access.
==1329==Hint: address points to the zero page.
    #0 0x7fa931ad765f  /tmp/portage/sys-libs/glibc-2.23-r3/work/glibc-2.23/nptl/pthread_join.c:34
    #1 0x53ee0d in join_pthread /tmp/portage/app-arch/lrzip-0.631/work/lrzip-0.631/stream.c:147:6
    #2 0x53ee0d in fill_buffer /tmp/portage/app-arch/lrzip-0.631/work/lrzip-0.631/stream.c:1697
    #3 0x53ee0d in read_stream /tmp/portage/app-arch/lrzip-0.631/work/lrzip-0.631/stream.c:1755
    #4 0x531075 in unzip_literal /tmp/portage/app-arch/lrzip-0.631/work/lrzip-0.631/runzip.c:162:16
    #5 0x531075 in runzip_chunk /tmp/portage/app-arch/lrzip-0.631/work/lrzip-0.631/runzip.c:320
    #6 0x531075 in runzip_fd /tmp/portage/app-arch/lrzip-0.631/work/lrzip-0.631/runzip.c:382
    #7 0x519b41 in decompress_file /tmp/portage/app-arch/lrzip-0.631/work/lrzip-0.631/lrzip.c:826:6
    #8 0x511074 in main /tmp/portage/app-arch/lrzip-0.631/work/lrzip-0.631/main.c:669:4
    #9 0x7fa930d3a78f in __libc_start_main 
/tmp/portage/sys-libs/glibc-2.23-r3/work/glibc-2.23/csu/../csu/libc-start.c:289
    #10 0x41abf8 in _init (/usr/bin/lrzip+0x41abf8)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV /tmp/portage/sys-libs/glibc-2.23-r3/work/glibc-2.23/nptl/pthread_join.c:34 
==1329==ABORTING

Affected version:
0.631

Fixed version:
N/A

Commit fix:
N/A

Credit:
This bug was discovered by Agostino Sarubbo of Gentoo.

CVE:
CVE-2017-8843

Reproducer:
https://github.com/asarubbo/poc/blob/master/00231-lrzip-nullptr-join_pthread

Timeline:
2017-03-24: bug discovered and reported to upstream
2017-05-07: blog post about the issue
2017-05-08: CVE assigned

Note:
This bug was found with American Fuzzy Lop.

Permalink:
https://blogs.gentoo.org/ago/2017/05/07/lrzip-null-pointer-dereference-in-join_pthread-stream-c/

--
Agostino Sarubbo
Gentoo Linux Developer