UBUNTU: SAUCE: apparmor: fix oops when racing to retrieve notification

BugLink: https://bugs.launchpad.net/bugs/2040245

When there is a race to receive a notification, the failing tasks
oopes when erroring

[  196.140988] BUG: kernel NULL pointer dereference, address: 0000000000000000
[  196.140995] #PF: supervisor read access in kernel mode
[  196.140996] #PF: error_code(0x0000) - not-present page
[  196.140997] PGD 0 P4D 0
[  196.140999] Oops: 0000 [#1] PREEMPT SMP NOPTI
[  196.141001] CPU: 0 PID: 2316 Comm: aa-prompt Not tainted 6.5.0-9-generic #9-Ubuntu
[  196.141004] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014
[  196.141005] RIP: 0010:aa_listener_unotif_recv+0x11d/0x260
[  196.141011] Code: ff ff ff 8b 55 d0 48 8b 75 c8 4c 89 ef e8 6b db ff ff 49 89 c2 48 85 c0 0f 88 c0 00 00 00 0f 84 25 ff ff ff 8b 05 3b 1c 1f 03 <49> 8b 55 00 83 e0 20 83 7a 08 07 74 66 85 c0 0f 85 01 01 00 00 48
[  196.141012] RSP: 0018:ffffa2674075fdd8 EFLAGS: 00010246
[  196.141014] RAX: 0000000000000000 RBX: ffff974507a08404 RCX: 0000000000000000
[  196.141017] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
[  196.141017] RBP: ffffa2674075fe10 R08: 0000000000000000 R09: 0000000000000000
[  196.141018] R10: fffffffffffffffe R11: 0000000000000000 R12: ffff974507a08400
[  196.141019] R13: 0000000000000000 R14: ffff974507a08430 R15: ffff97451de00a00
[  196.141020] FS:  00007f4ab6b30740(0000) GS:ffff97486fa00000(0000) knlGS:0000000000000000
[  196.141022] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  196.141024] CR2: 0000000000000000 CR3: 0000000104cf2003 CR4: 0000000000770ef0
[  196.141026] PKRU: 55555554
[  196.141027] Call Trace:
[  196.141032]  <TASK>
[  196.141034]  ? show_regs+0x6d/0x80
[  196.141041]  ? __die+0x24/0x80
[  196.141043]  ? page_fault_oops+0x99/0x1b0
[  196.141047]  ? do_user_addr_fault+0x316/0x6b0
[  196.141048]  ? filemap_map_pages+0x2b3/0x460
[  196.141056]  ? exc_page_fault+0x83/0x1b0
[  196.141068]  ? asm_exc_page_fault+0x27/0x30
[  196.141079]  ? aa_listener_unotif_recv+0x11d/0x260
[  196.141081]  ? aa_listener_unotif_recv+0x184/0x260
[  196.141083]  listener_ioctl+0x1e1/0x260
[  196.141088]  __x64_sys_ioctl+0xa0/0xf0
[  196.141092]  do_syscall_64+0x59/0x90
[  196.141094]  ? do_user_addr_fault+0x238/0x6b0
[  196.141095]  ? exit_to_user_mode_prepare+0x30/0xb0
[  196.141100]  ? irqentry_exit_to_user_mode+0x17/0x20
[  196.141104]  ? irqentry_exit+0x43/0x50
[  196.141106]  ? exc_page_fault+0x94/0x1b0
[  196.141107]  entry_SYSCALL_64_after_hwframe+0x6e/0xd8
[  196.141109] RIP: 0033:0x7f4ab69238ef
[  196.141124] Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 18 48 8b 44 24 18 64 48 2b 04 25 28 00 00
[  196.141125] RSP: 002b:00007ffd607a9020 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[  196.141127] RAX: ffffffffffffffda RBX: 00007ffd607a9100 RCX: 00007f4ab69238ef
[  196.141128] RDX: 00007ffd607a9100 RSI: 00000000c008f804 RDI: 0000000000000003
[  196.141128] RBP: 0000000000000003 R08: 0000000000000001 R09: 00007f4ab6b30740
[  196.141129] R10: 00007f4ab6b7f0a0 R11: 0000000000000246 R12: 00007ffd607a90a0
[  196.141130] R13: 00007ffd607a90dc R14: 0000559564822c10 R15: 0000000000031000
[  196.141131]  </TASK>
[  196.141132] Modules linked in: snd_seq_dummy snd_hrtimer binfmt_misc nls_iso8859_1 intel_rapl_msr intel_rapl_common snd_hda_codec_generic ledtrig_audio snd_hda_intel snd_intel_dspcfg snd_intel_sdw_acpi snd_hda_codec snd_hda_core snd_hwdep snd_pcm kvm_intel snd_seq_midi snd_seq_midi_event kvm irqbypass crct10dif_pclmul polyval_clmulni polyval_generic ghash_clmulni_intel aesni_intel crypto_simd cryptd rapl joydev snd_rawmidi snd_seq i2c_i801 i2c_smbus snd_seq_device snd_timer qxl snd drm_ttm_helper lpc_ich soundcore ttm 9pnet_virtio 9pnet drm_kms_helper input_leds mac_hid serio_raw nfsd msr parport_pc auth_rpcgss ppdev nfs_acl lockd grace lp parport drm efi_pstore sunrpc dmi_sysfs qemu_fw_cfg ip_tables x_tables autofs4 hid_generic usbhid hid ahci crc32_pclmul psmouse xhci_pci libahci virtio_rng xhci_pci_renesas
[  196.141188] CR2: 0000000000000000
[  196.141190] ---[ end trace 0000000000000000 ]---

Fixes: e074176 ("UBUNTU: SAUCE: apparmor4.0.0 [61/76]: prompt - refactor to moving caching to uresponse")
Signed-off-by: John Johansen <[email protected]>
Acked-by: Tim Gardner <[email protected]>
Acked-by: Stefan Bader <[email protected]>
Signed-off-by: Roxana Nicolescu <[email protected]>

Author: jrjohansen

security/apparmor/notify.c

@@ -1023,8 +1023,7 @@ long aa_listener_unotif_recv(struct aa_listener *listener, void __user *buf,
 	do {
 		knotif = listener_pop_and_hold_knotif(listener);
 		if (!knotif) {
-			ret = -ENOENT;
-			break;
+			return -ENOENT;
 		}
 		AA_DEBUG(DEBUG_UPCALL, "id %lld: removed notif from listener queue",
 			 knotif->id);