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Subject[PATCH 5.7 121/244] apparmor: ensure that dfa state tables have entries
Date
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))

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