bpf: Add bpf_mem_alloc_check_size() helper

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>

diff --git a/include/linux/bpf_mem_alloc.h b/include/linux/bpf_mem_alloc.h
index aaf004d943228af86aab2f6cf6694f9f48859e07..e45162ef59bb1a6d65489a26ce6f0b2d5cfb0bef 100644 (file)
--- a/include/linux/bpf_mem_alloc.h
+++ b/include/linux/bpf_mem_alloc.h
@@ -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);
 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: */
 void *bpf_mem_alloc(struct bpf_mem_alloc *ma, size_t size);
 void bpf_mem_free(struct bpf_mem_alloc *ma, void *ptr);

diff --git a/kernel/bpf/memalloc.c b/kernel/bpf/memalloc.c
index b3858a76e0b35891342810f9eb6cdcacf9690d9b..146f5b57cfb1cbffd7bb95aaeb01884f62ec6ab5 100644 (file)
--- a/kernel/bpf/memalloc.c
+++ b/kernel/bpf/memalloc.c
@@ -35,6 +35,8 @@
  */
 #define LLIST_NODE_SZ sizeof(struct llist_node)
 
+#define BPF_MEM_ALLOC_SIZE_MAX 4096
+
 /* similar to kmalloc, but sizeof == 8 bucket is gone */
 static u8 size_index[24] __ro_after_init = {
        3,      /* 8 */
@@ -65,7 +67,7 @@ static u8 size_index[24] __ro_after_init = {
 
 static int bpf_mem_cache_idx(size_t size)
 {
-       if (!size || size > 4096)
+       if (!size || size > BPF_MEM_ALLOC_SIZE_MAX)
                return -1;
 
        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;
 }
+
+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;
+}