Frantisek Sumsal
909eb4c01d
We can't dereference the variant object directly, as it might be
a magic object (which has an address on a faulting page); use
json_variant_is_sensitive() instead that handles this case.
For example, with an empty array:
==1547789==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000023 (pc 0x7fd616ca9a18 bp 0x7ffcba1dc7c0 sp 0x7ffcba1dc6d0 T0)
==1547789==The signal is caused by a READ memory access.
==1547789==Hint: address points to the zero page.
SCARINESS: 10 (null-deref)
#0 0x7fd616ca9a18 in json_variant_strv ../src/shared/json.c:2190
#1 0x408332 in oci_args ../src/nspawn/nspawn-oci.c:173
#2 0x7fd616cc09ce in json_dispatch ../src/shared/json.c:4400
#3 0x40addf in oci_process ../src/nspawn/nspawn-oci.c:428
#4 0x7fd616cc09ce in json_dispatch ../src/shared/json.c:4400
#5 0x41fef5 in oci_load ../src/nspawn/nspawn-oci.c:2187
#6 0x4061e4 in LLVMFuzzerTestOneInput ../src/nspawn/fuzz-nspawn-oci.c:23
#7 0x40691c in main ../src/fuzz/fuzz-main.c:50
#8 0x7fd61564a50f in __libc_start_call_main (/lib64/libc.so.6+0x2750f)
#9 0x7fd61564a5c8 in __libc_start_main@GLIBC_2.2.5 (/lib64/libc.so.6+0x275c8)
#10 0x405da4 in _start (/home/fsumsal/repos/@systemd/systemd/build-san/fuzz-nspawn-oci+0x405da4)
DEDUP_TOKEN: json_variant_strv--oci_args--json_dispatch
AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV ../src/shared/json.c:2190 in json_variant_strv
==1547789==ABORTING
Or with an empty string in an array:
../src/shared/json.c:2202:39: runtime error: member access within misaligned address 0x000000000007 for type 'struct JsonVariant', which requires 8 byte alignment
0x000000000007: note: pointer points here
<memory cannot be printed>
#0 0x7f35f4ca9bcf in json_variant_strv ../src/shared/json.c:2202
#1 0x408332 in oci_args ../src/nspawn/nspawn-oci.c:173
#2 0x7f35f4cc09ce in json_dispatch ../src/shared/json.c:4400
#3 0x40addf in oci_process ../src/nspawn/nspawn-oci.c:428
#4 0x7f35f4cc09ce in json_dispatch ../src/shared/json.c:4400
#5 0x41fef5 in oci_load ../src/nspawn/nspawn-oci.c:2187
#6 0x4061e4 in LLVMFuzzerTestOneInput ../src/nspawn/fuzz-nspawn-oci.c:23
#7 0x40691c in main ../src/fuzz/fuzz-main.c:50
#8 0x7f35f364a50f in __libc_start_call_main (/lib64/libc.so.6+0x2750f)
#9 0x7f35f364a5c8 in __libc_start_main@GLIBC_2.2.5 (/lib64/libc.so.6+0x275c8)
#10 0x405da4 in _start (/home/fsumsal/repos/@systemd/systemd/build-san/fuzz-nspawn-oci+0x405da4)
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior ../src/shared/json.c:2202:39 in
Note: this happens only if json_variant_copy() in json_variant_set_source() fails.
Found by Nallocfuzz.
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