apparmor: check accept index + 1 is in bounds

aa_lookup_condperms() returns perms[index + 1] when an accept entry has
ACCEPT_FLAG_OWNER set and the subject uid does not match the file uid,
so such an entry consumes two slots in the perms table.  But
verify_dfa_accept_index() only checks that index is within the perms
table, so a policy that sets the owner flag on the last entry is
accepted, and the runtime lookup then reads perms[index + 1] one entry
past the end of the table.

The perms table is allocated by unpack_perms_table() with a u16 size
read from the policy blob, so a crafted policy can place the owner flag
at index size - 1 to reach the out-of-bounds read.

Check that index + 1 is also in bounds when the owner flag is set.

Fixes: 6f442d42c0d89 ("apparmor: fix profile verification and enable it")
Cc: stable@vger.kernel.org
Signed-off-by: Guanglei Zhu <zhugl3@xiaopeng.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>

0 files changed, 0 insertions, 0 deletions