Comment 3 for bug 1948470

Test with bionic-proposed (4.15.0-162.170)
---

Original:

# ../openat
Killed

[ 442.526300] BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
...
[ 442.539854] CPU: 1 PID: 5644 Comm: openat Not tainted 4.15.0-162-generic #170-Ubuntu
[ 442.540733] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
[ 442.541755] RIP: 0010:aa_path_name+0x55/0x370
...
[ 442.549808] Call Trace:
[ 442.550211] path_name+0x60/0xe0
[ 442.550687] profile_path_perm.part.7+0x57/0xa0
[ 442.551293] aa_path_perm+0xe2/0x130
[ 442.551819] common_perm+0x59/0x130
[ 442.552323] common_perm_cond+0x4c/0x70
[ 442.552856] apparmor_inode_getattr+0x1d/0x20
[ 442.553444] security_inode_getattr+0x47/0x60
[ 442.554038] vfs_getattr+0x21/0x40
[ 442.554538] vfsub_update_h_iattr+0x95/0xb0 [aufs]
[ 442.555172] ? __lookup_hash+0x22/0xa0
[ 442.555697] ? lookup_one_len+0x113/0x120
[ 442.556323] vfsub_lookup_one_len+0x50/0x70 [aufs]
[ 442.557065] au_wh_test+0x25/0xe0 [aufs]
[ 442.557615] au_lkup_dentry+0x484/0x620 [aufs]
[ 442.558225] aufs_lookup.part.33+0x11c/0x210 [aufs]
[ 442.562787] aufs_atomic_open+0x102/0x3b0 [aufs]
[ 442.563427] ? aufs_permission+0x190/0x2d0 [aufs]
[ 442.564098] ? __inode_permission+0x5b/0x160
[ 442.564689] path_openat+0xde1/0x18b0
[ 442.565214] ? path_openat+0xde1/0x18b0
[ 442.565756] do_filp_open+0x9b/0x110
[ 442.566266] ? __check_object_size+0xc8/0x1b0
[ 442.566862] ? __alloc_fd+0xb2/0x170
[ 442.567376] do_sys_open+0x1ba/0x2c0
[ 442.567908] ? do_sys_open+0x1ba/0x2c0
[ 442.568453] SyS_openat+0x14/0x20
[ 442.568939] do_syscall_64+0x73/0x130
[ 442.569458] entry_SYSCALL_64_after_hwframe+0x41/0xa6
[ 442.570117] RIP: 0033:0x7f079564af83

Patched:

# ../openat
# echo $?
0

# uname -rv
4.15.0-162-generic #170+test20211022b1 SMP Fri Oct 22 10:59:39 -03 2021