From: John Johansen john.johansen@canonical.com
commit c27c6bd2c4d6b6bb779f9b722d5607993e1d5e5c upstream.
Currently it is possible to specify a state machine table with 0 length, this is not valid as optional tables are specified by not defining the table as present. Further this allows by-passing the base tables range check against the next/check tables.
Fixes: d901d6a298dc ("apparmor: dfa split verification of table headers") Reported-by: Mike Salvatore mike.salvatore@canonical.com Signed-off-by: John Johansen john.johansen@canonical.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- security/apparmor/match.c | 5 +++++ 1 file changed, 5 insertions(+)
--- a/security/apparmor/match.c +++ b/security/apparmor/match.c @@ -97,6 +97,9 @@ static struct table_header *unpack_table th.td_flags == YYTD_DATA8)) goto out;
+ /* if we have a table it must have some entries */ + if (th.td_lolen == 0) + goto out; tsize = table_size(th.td_lolen, th.td_flags); if (bsize < tsize) goto out; @@ -198,6 +201,8 @@ static int verify_dfa(struct aa_dfa *dfa
state_count = dfa->tables[YYTD_ID_BASE]->td_lolen; trans_count = dfa->tables[YYTD_ID_NXT]->td_lolen; + if (state_count == 0) + goto out; for (i = 0; i < state_count; i++) { if (!(BASE_TABLE(dfa)[i] & MATCH_FLAG_DIFF_ENCODE) && (DEFAULT_TABLE(dfa)[i] >= state_count))