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:
[ 2.405293] __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.
Cc: <stable@xxxxxxxxxxxxxxx> # 6.11.x
Fixes: b32801d1255b ("mm/slab: Introduce kmem_buckets_create() and family")
Signed-off-by: Koichiro Den <koichiro.den@xxxxxxxxx>
---
Changes in v2:
- Simplify by just reusing calculated aligned size stored in
the default kmalloc_caches
---
mm/slab_common.c | 36 +++++++++++++++++++++++-------------
1 file changed, 23 insertions(+), 13 deletions(-)
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 3d26c257ed8b..db6ffe53c23e 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -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 +426,29 @@ 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,
- 0, flags, cache_useroffset,
- cache_usersize, ctor);
- kfree(cache_name);
- if (WARN_ON(!(*b)[idx]))
- goto fail;
+
+ 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);
+ if (WARN_ON(!(*b)[aligned_idx])) {
+ kfree(cache_name);
+ 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);
--
2.43.0
