From: John Johansen <john.johan...@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.salvat...@canonical.com>
Signed-off-by: John Johansen <john.johan...@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
security/apparmor/match.c | 5 +++++
1 file changed, 5 insertions(+)
--- a/security/apparmor/match.c
+++ b/security/apparmor/match.c
@@ -101,6 +101,9 @@ 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;
@@ -202,6 +205,8 @@ 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))
