diff options
| author | Massimiliano Pellizzer <massimiliano.pellizzer@canonical.com> | 2026-01-15 15:30:50 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2026-03-13 17:26:03 +0100 |
| commit | 3bb7db43e32190c973d4019037cedb7895920184 (patch) | |
| tree | 4d1809c625c8c5e5407ea6d9f14e5f081c8f7734 /security | |
| parent | 9deda0fcda5c1f388c5e279541850b71a2ccfcf4 (diff) | |
apparmor: validate DFA start states are in bounds in unpack_pdb
commit 9063d7e2615f4a7ab321de6b520e23d370e58816 upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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 dd602bd5fca9..96d441129234 100644 --- a/security/apparmor/policy_unpack.c +++ b/security/apparmor/policy_unpack.c @@ -770,7 +770,17 @@ 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); |