bpf: Fix error usage of map_fd and fdget() in generic_map_update_batch()

1. The ufd in generic_map_update_batch() should be read from batch.map_fd;
2. A call to fdget() should be followed by a symmetric call to fdput().

Fixes: aa2e93b8e58e ("bpf: Add generic support for update and delete batch ops")
Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211019032934.1210517-1-xukuohai@huawei.com

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 4e50c0b..9dab49d 100644 (file)
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1337,12 +1337,11 @@ int generic_map_update_batch(struct bpf_map *map,
        void __user *values = u64_to_user_ptr(attr->batch.values);
        void __user *keys = u64_to_user_ptr(attr->batch.keys);
        u32 value_size, cp, max_count;
-       int ufd = attr->map_fd;
+       int ufd = attr->batch.map_fd;
        void *key, *value;
        struct fd f;
        int err = 0;
 
-       f = fdget(ufd);
        if (attr->batch.elem_flags & ~BPF_F_LOCK)
                return -EINVAL;
 
@@ -1367,6 +1366,7 @@ int generic_map_update_batch(struct bpf_map *map,
                return -ENOMEM;
        }
 
+       f = fdget(ufd); /* bpf_map_do_batch() guarantees ufd is valid */
        for (cp = 0; cp < max_count; cp++) {
                err = -EFAULT;
                if (copy_from_user(key, keys + cp * map->key_size,
@@ -1386,6 +1386,7 @@ int generic_map_update_batch(struct bpf_map *map,
 
        kvfree(value);
        kvfree(key);
+       fdput(f);
        return err;
 }