[Bug 15871] New: [busybox 1.36.1] use-after-free in awk

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=15871

            Bug ID: 15871
           Summary: [busybox 1.36.1] use-after-free in awk
           Product: Busybox
           Version: unspecified
          Hardware: All
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P5
         Component: Other
          Assignee: unassigned at busybox.net
          Reporter: zclin21 at gmail.com
                CC: busybox-cvs at busybox.net
  Target Milestone: ---

Hi, busybox developers,
We found a use-after-free vulnerability in awk applet of busybox v1.36.1. The
affected component is awk.c:1064 in copyvar 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]:

==32093==ERROR: AddressSanitizer: heap-use-after-free on address 0x606000003080
at pc 0x000000e7dfe2 bp 0x7fff6ee9b930 sp 0x7fff6ee9b928
READ of size 4 at 0x606000003080 thread T0
    #0 0xe7dfe1 
(/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+0xe7dfe1)
    #1 0xe4bbdf 
(/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+0xe4bbdf)
    #2 0xe4eb16 
(/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+0xe4eb16)
    #3 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)
    #4 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)
    #5 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)
    #6 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)
    #7 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)
    #8 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)
    #9 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)
    #10 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)
    #11 0x7f8358526c86  (/lib/x86_64-linux-gnu/libc.so.6+0x21c86)
    #12 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)

0x606000003080 is located 0 bytes inside of 64-byte region
[0x606000003080,0x6060000030c0)
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 0xe4eb16 
(/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+0xe4eb16)
    #4 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)
    #5 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)
    #6 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)
    #7 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 0xe4eb16 
(/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+0xe4eb16)
    #4 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)
    #5 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)
    #6 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)
    #7 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+0xe7dfe1)


[line number]:

addr2line -e ./busybox_unstripped 0xe7dfe1
.../busybox-1_36_1/editors/awk.c:1064

Best wishes,
Zclin

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