On Fri, Dec 24, 2021 at 8:09 PM Christian Göttsche <cgzones@xxxxxxxxxxxxxx> wrote: > > 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, #42735, #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> > Someday it would be nice to have this validation of contexts done with the other policydb validation, but I don't want to mess with that right now. Acked-by: James Carter <jwcart2@xxxxxxxxx> > --- > v2: also check the entry is non-null > > --- > libsepol/src/expand.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/libsepol/src/expand.c b/libsepol/src/expand.c > index 8a7259a0..898e6b87 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 || !p->p_sens_val_to_name[sl->sens - 1]) > + 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 >
