Commit 9c9201af authored Nov 05, 2024 by Koichiro Den Committed by Vlastimil Babka Nov 05, 2024

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



Commit b035f5a6 ("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:
[    2.405293]  __kmem_cache_create_args+0xb8/0x3b0
[    2.405305]  kmem_buckets_create+0xfc/0x320
[    2.405315]  init_msg_buckets+0x34/0x78
[    2.405326]  do_one_initcall+0x64/0x3c8
[    2.405337]  kernel_init_freeable+0x26c/0x578
[    2.405348]  kernel_init+0x3c/0x258
[    2.405360]  ret_from_fork+0x10/0x20
[    2.405370] ---[ end trace 0000000000000000 ]---

To address this, alias kmem_cache for sizes smaller than min alignment
to the aligned sized kmem_cache, as done with the default system kmalloc
bucket.

Fixes: b32801d1 ("mm/slab: Introduce kmem_buckets_create() and family")
Cc: <stable@vger.kernel.org> # v6.11+
Signed-off-by: Koichiro Den <koichiro.den@gmail.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

parent 70457385

mm/slab_common.c

+20 −11

Original line number	Diff line number	Diff line
		@@ -380,8 +380,11 @@ kmem_buckets kmem_buckets_create(const char name, slab_flags_t flags,
		unsigned int usersize,
		void (ctor)(void ))
		{
		unsigned long mask = 0;
		unsigned int idx;
		kmem_buckets *b;
		int idx;

		BUILD_BUG_ON(ARRAY_SIZE(kmalloc_caches[KMALLOC_NORMAL]) > BITS_PER_LONG);

		/*
		* When the separate buckets API is not built in, just return
		@@ -403,7 +406,7 @@ kmem_buckets kmem_buckets_create(const char name, slab_flags_t flags,
		for (idx = 0; idx < ARRAY_SIZE(kmalloc_caches[KMALLOC_NORMAL]); idx++) {
		char short_size, cache_name;
		unsigned int cache_useroffset, cache_usersize;
		unsigned int size;
		unsigned int size, aligned_idx;

		if (!kmalloc_caches[KMALLOC_NORMAL][idx])
		continue;
		@@ -416,10 +419,6 @@ kmem_buckets kmem_buckets_create(const char name, slab_flags_t flags,
		if (WARN_ON(!short_size))
		goto fail;

		cache_name = kasprintf(GFP_KERNEL, "%s-%s", name, short_size + 1);
		if (WARN_ON(!cache_name))
		goto fail;

		if (useroffset >= size) {
		cache_useroffset = 0;
		cache_usersize = 0;
		@@ -427,18 +426,28 @@ kmem_buckets kmem_buckets_create(const char name, slab_flags_t flags,
		cache_useroffset = useroffset;
		cache_usersize = min(size - cache_useroffset, usersize);
		}
		(*b)[idx] = kmem_cache_create_usercopy(cache_name, size,

		aligned_idx = __kmalloc_index(size, false);
		if (!(*b)[aligned_idx]) {
		cache_name = kasprintf(GFP_KERNEL, "%s-%s", name, short_size + 1);
		if (WARN_ON(!cache_name))
		goto fail;
		(*b)[aligned_idx] = kmem_cache_create_usercopy(cache_name, size,
		0, flags, cache_useroffset,
		cache_usersize, ctor);
		kfree(cache_name);
		if (WARN_ON(!(*b)[idx]))
		if (WARN_ON(!(*b)[aligned_idx]))
		goto fail;
		set_bit(aligned_idx, &mask);
		}
		if (idx != aligned_idx)
		(b)[idx] = (b)[aligned_idx];
		}

		return b;

		fail:
		for (idx = 0; idx < ARRAY_SIZE(kmalloc_caches[KMALLOC_NORMAL]); idx++)
		for_each_set_bit(idx, &mask, ARRAY_SIZE(kmalloc_caches[KMALLOC_NORMAL]))
		kmem_cache_destroy((*b)[idx]);
		kmem_cache_free(kmem_buckets_cache, b);