mm/slab: fix warning caused by duplicate kmem_cache creation in kmem_buckets_create

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

mm/slab: fix warning caused by duplicate kmem_cache creation in kmem_buckets_create

Commit b035f5a6d852 ("mm: slab: reduce the kmalloc() minimum alignment

if DMA bouncing possible") reduced ARCH_KMALLOC_MINALIGN to 8 on arm64.

However, with KASAN_HW_TAGS enabled, arch_slab_minalign() becomes 16.

This causes kmalloc_caches[*][8] to be aliased to kmalloc_caches[*][16],

resulting in kmem_buckets_create() attempting to create a kmem_cache for

size 16 twice. This duplication triggers warnings on boot:

[ 2.325108] ------------[ cut here ]------------

[ 2.325135] kmem_cache of name 'memdup_user-16' already exists

[ 2.325783] WARNING: CPU: 0 PID: 1 at mm/slab_common.c:107 __kmem_cache_create_args+0xb8/0x3b0

[ 2.327957] Modules linked in:

[ 2.328550] CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.12.0-rc5mm-unstable-arm64+ #12

[ 2.328683] Hardware name: QEMU QEMU Virtual Machine, BIOS 2024.02-2 03/11/2024

[ 2.328790] pstate: 61000009 (nZCv daif -PAN -UAO -TCO +DIT -SSBS BTYPE=--)

[ 2.328911] pc : __kmem_cache_create_args+0xb8/0x3b0

[ 2.328930] lr : __kmem_cache_create_args+0xb8/0x3b0

[ 2.328942] sp : ffff800083d6fc50

[ 2.328961] x29: ffff800083d6fc50 x28: f2ff0000c1674410 x27: ffff8000820b0598

[ 2.329061] x26: 000000007fffffff x25: 0000000000000010 x24: 0000000000002000

[ 2.329101] x23: ffff800083d6fce8 x22: ffff8000832222e8 x21: ffff800083222388

[ 2.329118] x20: f2ff0000c1674410 x19: f5ff0000c16364c0 x18: ffff800083d80030

[ 2.329135] x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000

[ 2.329152] x14: 0000000000000000 x13: 0a73747369786520 x12: 79646165726c6120

[ 2.329169] x11: 656820747563205b x10: 2d2d2d2d2d2d2d2d x9 : 0000000000000000

[ 2.329194] x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000

[ 2.329210] x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000000

[ 2.329226] x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000000

[ 2.329291] Call trace:

[ 2.329407] __kmem_cache_create_args+0xb8/0x3b0

[ 2.329499] kmem_buckets_create+0xfc/0x320

[ 2.329526] init_user_buckets+0x34/0x78

[ 2.329540] do_one_initcall+0x64/0x3c8

[ 2.329550] kernel_init_freeable+0x26c/0x578

[ 2.329562] kernel_init+0x3c/0x258

[ 2.329574] ret_from_fork+0x10/0x20

[ 2.329698] ---[ end trace 0000000000000000 ]---

[ 2.403704] ------------[ cut here ]------------

[ 2.404716] kmem_cache of name 'msg_msg-16' already exists

[ 2.404801] WARNING: CPU: 2 PID: 1 at mm/slab_common.c:107 __kmem_cache_create_args+0xb8/0x3b0

[ 2.404842] Modules linked in:

[ 2.404971] CPU: 2 UID: 0 PID: 1 Comm: swapper/0 Tainted: G W 6.12.0-rc5mm-unstable-arm64+ #12

[ 2.405026] Tainted: [W]=WARN

[ 2.405043] Hardware name: QEMU QEMU Virtual Machine, BIOS 2024.02-2 03/11/2024

[ 2.405057] pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)

[ 2.405079] pc : __kmem_cache_create_args+0xb8/0x3b0

[ 2.405100] lr : __kmem_cache_create_args+0xb8/0x3b0

[ 2.405111] sp : ffff800083d6fc50

[ 2.405115] x29: ffff800083d6fc50 x28: fbff0000c1674410 x27: ffff8000820b0598

[ 2.405135] x26: 000000000000ffd0 x25: 0000000000000010 x24: 0000000000006000

[ 2.405153] x23: ffff800083d6fce8 x22: ffff8000832222e8 x21: ffff800083222388

[ 2.405169] x20: fbff0000c1674410 x19: fdff0000c163d6c0 x18: ffff800083d80030

[ 2.405185] x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000

[ 2.405201] x14: 0000000000000000 x13: 0a73747369786520 x12: 79646165726c6120

[ 2.405217] x11: 656820747563205b x10: 2d2d2d2d2d2d2d2d x9 : 0000000000000000

[ 2.405233] x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000

[ 2.405248] x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000000

[ 2.405271] x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000000

[ 2.405287] Call trace:

[ 2

---truncated---