Check the sensitivity is valid and thus the lookup in the name array
`p_sens_val_to_name` is valid.
Found by oss-fuzz (#42729, #42730, #42741)
==54784==The signal is caused by a READ memory access.
#0 0x5a10f3 in mls_semantic_level_expand ./selinux/libsepol/src/expand.c:934:11
#1 0x53839e in policydb_user_cache ./selinux/libsepol/src/policydb.c:972:7
#2 0x5c6325 in hashtab_map ./selinux/libsepol/src/hashtab.c:236:10
#3 0x5392e9 in policydb_index_others ./selinux/libsepol/src/policydb.c:1274:6
#4 0x53f90a in policydb_read ./selinux/libsepol/src/policydb.c:4496:6
#5 0x50c679 in LLVMFuzzerTestOneInput ./selinux/libsepol/fuzz/binpolicy-fuzzer.c:35:6
#6 0x4409e3 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) (./selinux/out/binpolicy-fuzzer+0x4409e3)
#7 0x4295bf in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) (./selinux/out/binpolicy-fuzzer+0x4295bf)
#8 0x42f850 in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) (./selinux/out/binpolicy-fuzzer+0x42f850)
#9 0x45b6d2 in main (./selinux/out/binpolicy-fuzzer+0x45b6d2)
#10 0x7f059fcd71c9 in __libc_start_call_main csu/../sysdeps/nptl/libc_start_call_main.h:58:16
#11 0x7f059fcd7277 in __libc_start_main csu/../csu/libc-start.c:409:3
#12 0x423900 in _start (./out/binpolicy-fuzzer+0x423900)
Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
---
libsepol/src/expand.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/libsepol/src/expand.c b/libsepol/src/expand.c
index 8a7259a0..db43d860 100644
--- a/libsepol/src/expand.c
+++ b/libsepol/src/expand.c
@@ -929,6 +929,10 @@ int mls_semantic_level_expand(mls_semantic_level_t * sl, mls_level_t * l,
if (!sl->sens)
return 0;
+ /* Invalid sensitivity */
+ if (sl->sens > p->p_levels.nprim)
+ return -1;
+
l->sens = sl->sens;
levdatum = (level_datum_t *) hashtab_search(p->p_levels.table,
p->p_sens_val_to_name[l->sens - 1]);
--
2.34.1
