Slab out-of-bound on sendmsg() failure

Issue

• Slab out-of-bound on sendmsg() failure causes the redzone being overwritten:

[66199.102505] =============================================================================
[66199.201050] BUG kmalloc-4k (Tainted: G          I      --------- -  -): Redzone overwritten
[66199.301680] -----------------------------------------------------------------------------

[66199.418034] Disabling lock debugging due to kernel taint
[66199.418036] Kernel panic - not syncing: panic_on_taint set ...
[66199.488271] CPU: 0 PID: 568543 Comm: qemu-kvm Kdump: loaded Tainted: G    B     I      --------- -  - 4.18.0-305.28.1.el8_4.x86_64 #1
[66199.632928] Hardware name: HPE ProLiant DL360 Gen10/ProLiant DL360 Gen10, BIOS U32 07/16/2020
[66199.735655] Call Trace:
[66199.765018]  dump_stack+0x5c/0x80
[66199.804861]  panic+0xe7/0x2a9
[66199.840508]  add_taint.cold.10+0x28/0x28
[66199.887688]  slab_bug+0xa0/0xbc
[66199.925435]  check_bytes_and_report.cold.102+0x19/0x6e
[66199.987293]  check_object+0x198/0x280
[66200.031327]  free_debug_processing+0x132/0x210
[66200.084797]  ? vhost_net_release+0x96/0xd0 [vhost_net]
[66200.146650]  __slab_free+0x1eb/0x330
[66200.189632]  ? __wait_rcu_gp+0x112/0x140
[66200.236812]  ? rcu_accelerate_cbs_unlocked+0x80/0x80
[66200.296564]  vhost_net_release+0x96/0xd0 [vhost_net]
[66200.356319]  __fput+0xbe/0x250
[66200.393019]  task_work_run+0x8a/0xb0
[66200.436007]  exit_to_usermode_loop+0xeb/0xf0
[66200.487377]  do_syscall_64+0x198/0x1a0
[66200.532458]  entry_SYSCALL_64_after_hwframe+0x65/0xca
[66200.593261] RIP: 0033:0x7f1dce8bb977
[66200.636244] Code: 12 b8 03 00 00 00 0f 05 48 3d 00 f0 ff ff 77 3b c3 66 90 53 89 fb 48 83 ec 10 e8 e4 fb ff ff 89 df 89 c2 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 2b 89 d7 89 44 24 0c e8 26 fc ff ff 8b 44 24
[66200.862659] RSP: 002b:00007ffffc6aa810 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
[66200.953857] RAX: 0000000000000000 RBX: 0000000000000067 RCX: 00007f1dce8bb977
[66201.039813] RDX: 0000000000000000 RSI: 0000564f05dd5c20 RDI: 0000000000000067
[66201.125768] RBP: 0000000000000002 R08: 0000564f06ed83c0 R09: 0000000000000007
[66201.211727] R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000001
[66201.297682] R13: 0000564f05c43f70 R14: 0000000000000000 R15: 0000000000000000