[PATCH 5.10 38/77] bpf: Fix error usage of map_fd and fdget() in generic_map_update_batch()

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

From: Xu Kuohai <xukuohai@xxxxxxxxxx>

commit fda7a38714f40b635f5502ec4855602c6b33dad2 upstream.

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@xxxxxxxxxx>
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Link: https://lore.kernel.org/bpf/20211019032934.1210517-1-xukuohai@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 kernel/bpf/syscall.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1309,12 +1309,11 @@ int generic_map_update_batch(struct bpf_
 	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;
 
@@ -1339,6 +1338,7 @@ int generic_map_update_batch(struct bpf_
 		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,
@@ -1358,6 +1358,7 @@ int generic_map_update_batch(struct bpf_
 
 	kfree(value);
 	kfree(key);
+	fdput(f);
 	return err;
 }