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bpf: Add bpf_mem_alloc_check_size() helper

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Introduce bpf_mem_alloc_check_size() to check whether the allocation
size exceeds the limitation for the kmalloc-equivalent allocator. The
upper limit for percpu allocation is LLIST_NODE_SZ bytes larger than
non-percpu allocation, so a percpu argument is added to the helper.

The helper will be used in the following patch to check whether the size
parameter passed to bpf_mem_alloc() is too big.

Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20241030100516.3633640-3-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Hou Tao 2024-10-30 18:05:13 +08:00 committed by Alexei Starovoitov
parent 101ccfbabf
commit 62a898b07b
2 changed files with 16 additions and 1 deletions
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3
include/linux/bpf_mem_alloc.h
View File

@ -33,6 +33,9 @@ int bpf_mem_alloc_percpu_init(struct bpf_mem_alloc *ma, struct obj_cgroup *objcg
int bpf_mem_alloc_percpu_unit_init(struct bpf_mem_alloc *ma, int size); int bpf_mem_alloc_percpu_unit_init(struct bpf_mem_alloc *ma, int size);
void bpf_mem_alloc_destroy(struct bpf_mem_alloc *ma); void bpf_mem_alloc_destroy(struct bpf_mem_alloc *ma);
/* Check the allocation size for kmalloc equivalent allocator */
int bpf_mem_alloc_check_size(bool percpu, size_t size);
/* kmalloc/kfree equivalent: */ /* kmalloc/kfree equivalent: */
void *bpf_mem_alloc(struct bpf_mem_alloc *ma, size_t size); void *bpf_mem_alloc(struct bpf_mem_alloc *ma, size_t size);
void bpf_mem_free(struct bpf_mem_alloc *ma, void *ptr); void bpf_mem_free(struct bpf_mem_alloc *ma, void *ptr);

14
kernel/bpf/memalloc.c
View File

@ -35,6 +35,8 @@
*/ */
#define LLIST_NODE_SZ sizeof(struct llist_node) #define LLIST_NODE_SZ sizeof(struct llist_node)
#define BPF_MEM_ALLOC_SIZE_MAX 4096
/* similar to kmalloc, but sizeof == 8 bucket is gone */ /* similar to kmalloc, but sizeof == 8 bucket is gone */
static u8 size_index[24] __ro_after_init = { static u8 size_index[24] __ro_after_init = {
3, /* 8 */ 3, /* 8 */
@ -65,7 +67,7 @@ static u8 size_index[24] __ro_after_init = {
static int bpf_mem_cache_idx(size_t size) static int bpf_mem_cache_idx(size_t size)
{ {
if (!size || size > 4096) if (!size || size > BPF_MEM_ALLOC_SIZE_MAX)
return -1; return -1;
if (size <= 192) if (size <= 192)
@ -1005,3 +1007,13 @@ void notrace *bpf_mem_cache_alloc_flags(struct bpf_mem_alloc *ma, gfp_t flags)
return !ret ? NULL : ret + LLIST_NODE_SZ; return !ret ? NULL : ret + LLIST_NODE_SZ;
} }
int bpf_mem_alloc_check_size(bool percpu, size_t size)
{
/* The size of percpu allocation doesn't have LLIST_NODE_SZ overhead */
if ((percpu && size > BPF_MEM_ALLOC_SIZE_MAX) ||
(!percpu && size > BPF_MEM_ALLOC_SIZE_MAX - LLIST_NODE_SZ))
return -E2BIG;
return 0;
}