apparmor: Fix memory leak in unpack_profile()

The aa_put_pdb(rules->file) should be called when rules->file is
reassigned, otherwise there may be a memory leak.

This was found via kmemleak:

unreferenced object 0xffff986c17056600 (size 192):
  comm "apparmor_parser", pid 875, jiffies 4294893488
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 89 14 04 6c 98 ff ff  ............l...
    00 00 8c 11 6c 98 ff ff bc 0c 00 00 00 00 00 00  ....l...........
  backtrace (crc e28c80c4):
    [<ffffffffba25087f>] kmemleak_alloc+0x4f/0x90
    [<ffffffffb95ecd42>] kmalloc_trace+0x2d2/0x340
    [<ffffffffb98a7b3d>] aa_alloc_pdb+0x4d/0x90
    [<ffffffffb98ab3b8>] unpack_pdb+0x48/0x660
    [<ffffffffb98ac073>] unpack_profile+0x693/0x1090
    [<ffffffffb98acf5a>] aa_unpack+0x10a/0x6e0
    [<ffffffffb98a93e3>] aa_replace_profiles+0xa3/0x1210
    [<ffffffffb989a183>] policy_update+0x163/0x2a0
    [<ffffffffb989a381>] profile_replace+0xb1/0x130
    [<ffffffffb966cb64>] vfs_write+0xd4/0x3d0
    [<ffffffffb966d05b>] ksys_write+0x6b/0xf0
    [<ffffffffb966d10e>] __x64_sys_write+0x1e/0x30
    [<ffffffffba242316>] do_syscall_64+0x76/0x120
    [<ffffffffba4000e5>] entry_SYSCALL_64_after_hwframe+0x6c/0x74

So add aa_put_pdb(rules->file) to fix it when rules->file is reassigned.

Fixes: 98b824ff ("apparmor: refcount the pdb")
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>

security/apparmor/policy_unpack.c

@@ -1025,8 +1025,10 @@ static struct aa_profile *unpack_profile(struct aa_ext *e, char **ns_name)
 		}
 	} else if (rules->policy->dfa &&
 		   rules->policy->start[AA_CLASS_FILE]) {
+		aa_put_pdb(rules->file);
 		rules->file = aa_get_pdb(rules->policy);
 	} else {
+		aa_put_pdb(rules->file);
 		rules->file = aa_get_pdb(nullpdb);
 	}
 	error = -EPROTO;