CVE-2024-38578: Out-of-bounds Write

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