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

Greg Kroah-Hartman
2021-11-01T09:38:17Z

From: Xu Kuohai <xukuohai@huawei.com>

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@huawei.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211019032934.1210517-1-xukuohai@huawei.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
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;
}