diff options
| author | Massimiliano Pellizzer <massimiliano.pellizzer@canonical.com> | 2026-01-15 15:30:50 +0100 |
|---|---|---|
| committer | John Johansen <john.johansen@canonical.com> | 2026-03-09 16:05:42 -0700 |
| commit | 9063d7e2615f4a7ab321de6b520e23d370e58816 (patch) | |
| tree | 7f864e220ad12b531ddce35c747a97c5739a2edc /security | |
| parent | 1f318b96cc84d7c2ab792fcc0bfd42a7ca890681 (diff) | |
apparmor: validate DFA start states are in bounds in unpack_pdb
Start states are read from untrusted data and used as indexes into the
DFA state tables. The aa_dfa_next() function call in unpack_pdb() will
access dfa->tables[YYTD_ID_BASE][start], and if the start state exceeds
the number of states in the DFA, this results in an out-of-bound read.
==================================================================
BUG: KASAN: slab-out-of-bounds in aa_dfa_next+0x2a1/0x360
Read of size 4 at addr ffff88811956fb90 by task su/1097
...
Reject policies with out-of-bounds start states during unpacking
to prevent the issue.
Fixes: ad5ff3db53c6 ("AppArmor: Add ability to load extended policy")
Reported-by: Qualys Security Advisory <qsa@qualys.com>
Tested-by: Salvatore Bonaccorso <carnil@debian.org>
Reviewed-by: Georgia Garcia <georgia.garcia@canonical.com>
Reviewed-by: Cengiz Can <cengiz.can@canonical.com>
Signed-off-by: Massimiliano Pellizzer <massimiliano.pellizzer@canonical.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>
Diffstat (limited to 'security')
| -rw-r--r-- | security/apparmor/policy_unpack.c | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/security/apparmor/policy_unpack.c b/security/apparmor/policy_unpack.c index 1769417a9962..ba5d40dbeb24 100644 --- a/security/apparmor/policy_unpack.c +++ b/security/apparmor/policy_unpack.c @@ -1010,7 +1010,17 @@ static int unpack_pdb(struct aa_ext *e, struct aa_policydb **policy, if (!aa_unpack_u32(e, &pdb->start[AA_CLASS_FILE], "dfa_start")) { /* default start state for xmatch and file dfa */ pdb->start[AA_CLASS_FILE] = DFA_START; - } /* setup class index */ + } + + size_t state_count = pdb->dfa->tables[YYTD_ID_BASE]->td_lolen; + + if (pdb->start[0] >= state_count || + pdb->start[AA_CLASS_FILE] >= state_count) { + *info = "invalid dfa start state"; + goto fail; + } + + /* setup class index */ for (i = AA_CLASS_FILE + 1; i <= AA_CLASS_LAST; i++) { pdb->start[i] = aa_dfa_next(pdb->dfa, pdb->start[0], i); |