ecryptfs: Fix buffer size for tag 66 packet

In the Linux kernel, the following vulnerability has been resolved:

ecryptfs: Fix buffer size for tag 66 packet

The 'TAG 66 Packet Format' description is missing the cipher code and
checksum fields that are packed into the message packet. As a result,
the buffer allocated for the packet is 3 bytes too small and
write_tag_66_packet() will write up to 3 bytes past the end of the
buffer.

Fix this by increasing the size of the allocation so the whole packet
will always fit in the buffer.

This fixes the below kasan slab-out-of-bounds bug:

BUG: KASAN: slab-out-of-bounds in ecryptfs_generate_key_packet_set+0x7d6/0xde0
Write of size 1 at addr ffff88800afbb2a5 by task touch/181

CPU: 0 PID: 181 Comm: touch Not tainted 6.6.13-gnu #1 4c9534092be820851bb687b82d1f92a426598dc6
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2/GNU Guix 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x4c/0x70
print_report+0xc5/0x610
? ecryptfs_generate_key_packet_set+0x7d6/0xde0
? kasan_complete_mode_report_info+0x44/0x210
? ecryptfs_generate_key_packet_set+0x7d6/0xde0
kasan_report+0xc2/0x110
? ecryptfs_generate_key_packet_set+0x7d6/0xde0
__asan_store1+0x62/0x80
ecryptfs_generate_key_packet_set+0x7d6/0xde0
? __pfx_ecryptfs_generate_key_packet_set+0x10/0x10
? __alloc_pages+0x2e2/0x540
? __pfx_ovl_open+0x10/0x10 [overlay 30837f11141636a8e1793533a02e6e2e885dad1d]
? dentry_open+0x8f/0xd0
ecryptfs_write_metadata+0x30a/0x550
? __pfx_ecryptfs_write_metadata+0x10/0x10
? ecryptfs_get_lower_file+0x6b/0x190
ecryptfs_initialize_file+0x77/0x150
ecryptfs_create+0x1c2/0x2f0
path_openat+0x17cf/0x1ba0
? __pfx_path_openat+0x10/0x10
do_filp_open+0x15e/0x290
? __pfx_do_filp_open+0x10/0x10
? __kasan_check_write+0x18/0x30
? _raw_spin_lock+0x86/0xf0
? __pfx__raw_spin_lock+0x10/0x10
? __kasan_check_write+0x18/0x30
? alloc_fd+0xf4/0x330
do_sys_openat2+0x122/0x160
? __pfx_do_sys_openat2+0x10/0x10
__x64_sys_openat+0xef/0x170
? __pfx___x64_sys_openat+0x10/0x10
do_syscall_64+0x60/0xd0
entry_SYSCALL_64_after_hwframe+0x6e/0xd8
RIP: 0033:0x7f00a703fd67
Code: 25 00 00 41 00 3d 00 00 41 00 74 37 64 8b 04 25 18 00 00 00 85 c0 75 5b 44 89 e2 48 89 ee bf 9c ff ff ff b8 01 01 00 00 0f 05 <48> 3d 00 f0 ff ff 0f 87 85 00 00 00 48 83 c4 68 5d 41 5c c3 0f 1f
RSP: 002b:00007ffc088e30b0 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007ffc088e3368 RCX: 00007f00a703fd67
RDX: 0000000000000941 RSI: 00007ffc088e48d7 RDI: 00000000ffffff9c
RBP: 00007ffc088e48d7 R08: 0000000000000001 R09: 0000000000000000
R10: 00000000000001b6 R11: 0000000000000246 R12: 0000000000000941
R13: 0000000000000000 R14: 00007ffc088e48d7 R15: 00007f00a7180040
</TASK>

Allocated by task 181:
kasan_save_stack+0x2f/0x60
kasan_set_track+0x29/0x40
kasan_save_alloc_info+0x25/0x40
__kasan_kmalloc+0xc5/0xd0
__kmalloc+0x66/0x160
ecryptfs_generate_key_packet_set+0x6d2/0xde0
ecryptfs_write_metadata+0x30a/0x550
ecryptfs_initialize_file+0x77/0x150
ecryptfs_create+0x1c2/0x2f0
path_openat+0x17cf/0x1ba0
do_filp_open+0x15e/0x290
do_sys_openat2+0x122/0x160
__x64_sys_openat+0xef/0x170
do_syscall_64+0x60/0xd0
entry_SYSCALL_64_after_hwframe+0x6e/0xd8