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>
---
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
