Bug 15880

Created attachment 9685 [details]
POC file

Hi, busybox developers,
We found a use-after-free vulnerability in awk applet of busybox v1.36.1. The affected component is awk.c:1023 in getvar_i function. Following is the reproduction process, and we put the poc file in the attachment.
[1.] Environment
Ubuntu 18.04, 64 bit
BusyBox 1.36.1
Clang 6.0.0

[2.] Compilation
2.1 Modify the Makefile:
HOSTCC=clang -fsanitize=address
HOSTCXX=clang++ -fsanitize=address
CC=clang
CFLAGS=-fsanitize=address
CPPFLAGS=-fsanitize=address
LDFLAGS="-Wl,--allow-multiple-definition"
2.2 Modify the Config.in file, switch the following configs to y：
DEBUG: y
DEBUG_PESSIMIZE: y
FEATURE_CLEAN_UP: y
DEBUG_SANITIZE: y
2.3 Commands for compilation:
export ASAN_OPTIONS=detect_leaks=0
make defconfig
make install

[3.] Reproduction
export ASAN_OPTIONS="abort_on_error=1 symbolize=0"
./busybox_unstripped awk -f $poc ./awk_t1_input
[ASAN report]:
==13107==ERROR: AddressSanitizer: heap-use-after-free on address 0x606000003260 at pc 0x000000e5b7b4 bp 0x7ffc4399b170 sp 0x7ffc4399b168
READ of size 4 at 0x606000003260 thread T0
    #0 0xe5b7b3  (/home/zclin/afl-vul-score/llvm_mode/research/path-collect-all-new-0524/path-collect-all-new/busybox/reproduce/busybox-1_36_1/fuzz_check/awk/busybox_unstripped+0xe5b7b3)
    #1 0xe641e2  (/home/zclin/afl-vul-score/llvm_mode/research/path-collect-all-new-0524/path-collect-all-new/busybox/reproduce/busybox-1_36_1/fuzz_check/awk/busybox_unstripped+0xe641e2)
    #2 0xe5fcf2  (/home/zclin/afl-vul-score/llvm_mode/research/path-collect-all-new-0524/path-collect-all-new/busybox/reproduce/busybox-1_36_1/fuzz_check/awk/busybox_unstripped+0xe5fcf2)
    #3 0xe497e3  (/home/zclin/afl-vul-score/llvm_mode/research/path-collect-all-new-0524/path-collect-all-new/busybox/reproduce/busybox-1_36_1/fuzz_check/awk/busybox_unstripped+0xe497e3)
    #4 0xe4062d  (/home/zclin/afl-vul-score/llvm_mode/research/path-collect-all-new-0524/path-collect-all-new/busybox/reproduce/busybox-1_36_1/fuzz_check/awk/busybox_unstripped+0xe4062d)
    #5 0x50ac81  (/home/zclin/afl-vul-score/llvm_mode/research/path-collect-all-new-0524/path-collect-all-new/busybox/reproduce/busybox-1_36_1/fuzz_check/awk/busybox_unstripped+0x50ac81)
    #6 0x50dbaf  (/home/zclin/afl-vul-score/llvm_mode/research/path-collect-all-new-0524/path-collect-all-new/busybox/reproduce/busybox-1_36_1/fuzz_check/awk/busybox_unstripped+0x50dbaf)
    #7 0x51036d  (/home/zclin/afl-vul-score/llvm_mode/research/path-collect-all-new-0524/path-collect-all-new/busybox/reproduce/busybox-1_36_1/fuzz_check/awk/busybox_unstripped+0x51036d)
    #8 0x50db58  (/home/zclin/afl-vul-score/llvm_mode/research/path-collect-all-new-0524/path-collect-all-new/busybox/reproduce/busybox-1_36_1/fuzz_check/awk/busybox_unstripped+0x50db58)
    #9 0x50c3fd  (/home/zclin/afl-vul-score/llvm_mode/research/path-collect-all-new-0524/path-collect-all-new/busybox/reproduce/busybox-1_36_1/fuzz_check/awk/busybox_unstripped+0x50c3fd)
    #10 0x7f9c0a88bc86  (/lib/x86_64-linux-gnu/libc.so.6+0x21c86)
    #11 0x41e459  (/home/zclin/afl-vul-score/llvm_mode/research/path-collect-all-new-0524/path-collect-all-new/busybox/reproduce/busybox-1_36_1/fuzz_check/awk/busybox_unstripped+0x41e459)

0x606000003260 is located 0 bytes inside of 64-byte region [0x606000003260,0x6060000032a0)
freed by thread T0 here:
    #0 0x4dc500  (/home/zclin/afl-vul-score/llvm_mode/research/path-collect-all-new-0524/path-collect-all-new/busybox/reproduce/busybox-1_36_1/fuzz_check/awk/busybox_unstripped+0x4dc500)
    #1 0xe7f4ca  (/home/zclin/afl-vul-score/llvm_mode/research/path-collect-all-new-0524/path-collect-all-new/busybox/reproduce/busybox-1_36_1/fuzz_check/awk/busybox_unstripped+0xe7f4ca)
    #2 0xe4886f  (/home/zclin/afl-vul-score/llvm_mode/research/path-collect-all-new-0524/path-collect-all-new/busybox/reproduce/busybox-1_36_1/fuzz_check/awk/busybox_unstripped+0xe4886f)
    #3 0xe4062d  (/home/zclin/afl-vul-score/llvm_mode/research/path-collect-all-new-0524/path-collect-all-new/busybox/reproduce/busybox-1_36_1/fuzz_check/awk/busybox_unstripped+0xe4062d)
    #4 0x50ac81  (/home/zclin/afl-vul-score/llvm_mode/research/path-collect-all-new-0524/path-collect-all-new/busybox/reproduce/busybox-1_36_1/fuzz_check/awk/busybox_unstripped+0x50ac81)

previously allocated by thread T0 here:
    #0 0x4dc6d0  (/home/zclin/afl-vul-score/llvm_mode/research/path-collect-all-new-0524/path-collect-all-new/busybox/reproduce/busybox-1_36_1/fuzz_check/awk/busybox_unstripped+0x4dc6d0)
    #1 0x519df2  (/home/zclin/afl-vul-score/llvm_mode/research/path-collect-all-new-0524/path-collect-all-new/busybox/reproduce/busybox-1_36_1/fuzz_check/awk/busybox_unstripped+0x519df2)
    #2 0xe4886f  (/home/zclin/afl-vul-score/llvm_mode/research/path-collect-all-new-0524/path-collect-all-new/busybox/reproduce/busybox-1_36_1/fuzz_check/awk/busybox_unstripped+0xe4886f)
    #3 0xe4062d  (/home/zclin/afl-vul-score/llvm_mode/research/path-collect-all-new-0524/path-collect-all-new/busybox/reproduce/busybox-1_36_1/fuzz_check/awk/busybox_unstripped+0xe4062d)
    #4 0x50ac81  (/home/zclin/afl-vul-score/llvm_mode/research/path-collect-all-new-0524/path-collect-all-new/busybox/reproduce/busybox-1_36_1/fuzz_check/awk/busybox_unstripped+0x50ac81)

SUMMARY: AddressSanitizer: heap-use-after-free (/home/zclin/afl-vul-score/llvm_mode/research/path-collect-all-new-0524/path-collect-all-new/busybox/reproduce/busybox-1_36_1/fuzz_check/awk/busybox_unstripped+0xe5b7b3)


[line number]:

addr2line -e ./busybox_unstripped 0xe5b7b3
.../busybox-1_36_1/editors/awk.c:1023

Best wishes,
Zclin