On Tue, Feb 1, 2022 at 11:31 AM Christian Göttsche
<cgzones@xxxxxxxxxxxxxx> wrote:
>
> When converting an ebitmap into a string list, skip potential gaps in
> ebitmap_to_strs(). All converting functions like strs_to_str(),
> strs_write_each() and strs_write_each_indented() do already skip NULL
> elements, but sorting such a list will lead to a NULL dereference.
>
> #0 0x432ce5 in strcmp /src/llvm-project/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc:462:25
> #1 0x4f4893 in strs_cmp selinux/libsepol/src/kernel_to_common.c:258:9
> #2 0x47b74b in qsort_r /src/llvm-project/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc:9994:7
> #3 0x4f481d in strs_sort selinux/libsepol/src/kernel_to_common.c:266:2
> #4 0x4fe781 in attrmap_to_str selinux/libsepol/src/kernel_to_conf.c:1560:2
> #5 0x4fe781 in write_type_attribute_sets_to_conf selinux/libsepol/src/kernel_to_conf.c:1599:11
> #6 0x4f8098 in sepol_kernel_policydb_to_conf selinux/libsepol/src/kernel_to_conf.c:3182:7
> #7 0x4e0277 in LLVMFuzzerTestOneInput selinux/libsepol/fuzz/binpolicy-fuzzer.c:50:9
> #8 0x4d613b in main
> #9 0x7fa2d50260b2 in __libc_start_main /build/glibc-eX1tMB/glibc-2.31/csu/libc-start.c:308:16
> #10 0x41d4ed in _start
>
> Found by oss-fuzz (#44170)
>
> Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
Acked-by: James Carter <jwcart2@xxxxxxxxx>
> ---
> libsepol/src/kernel_to_common.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/libsepol/src/kernel_to_common.c b/libsepol/src/kernel_to_common.c
> index 9f5400c9..dc9e689e 100644
> --- a/libsepol/src/kernel_to_common.c
> +++ b/libsepol/src/kernel_to_common.c
> @@ -366,6 +366,9 @@ int ebitmap_to_strs(struct ebitmap *map, struct strs *strs, char **val_to_name)
> int rc;
>
> ebitmap_for_each_positive_bit(map, node, i) {
> + if (!val_to_name[i])
> + continue;
> +
> rc = strs_add(strs, val_to_name[i]);
> if (rc != 0) {
> return -1;
> --
> 2.34.1
>
