[PATCH 5.10 18/63] io_uring: use bottom half safe lock for fixed file data

Greg Kroah-Hartman
2021-01-04T16:09:02Z

From: Jens Axboe <axboe@kernel.dk>

commit ac0648a56c1ff66c1cbf735075ad33a26cbc50de upstream.

io_file_data_ref_zero() can be invoked from soft-irq from the RCU core,
hence we need to ensure that the file_data lock is bottom half safe. Use
the _bh() variants when grabbing this lock.

Reported-by: syzbot+1f4ba1e5520762c523c6@syzkaller.appspotmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/io_uring.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -7000,9 +7000,9 @@ static int io_sqe_files_unregister(struc
if (!data)
return -ENXIO;

- spin_lock(&data->lock);
+ spin_lock_bh(&data->lock);
ref_node = data->node;
- spin_unlock(&data->lock);
+ spin_unlock_bh(&data->lock);
if (ref_node)
percpu_ref_kill(&ref_node->refs);

@@ -7385,7 +7385,7 @@ static void io_file_data_ref_zero(struct
data = ref_node->file_data;
ctx = data->ctx;

- spin_lock(&data->lock);
+ spin_lock_bh(&data->lock);
ref_node->done = true;

while (!list_empty(&data->ref_list)) {
@@ -7397,7 +7397,7 @@ static void io_file_data_ref_zero(struct
list_del(&ref_node->node);
first_add |= llist_add(&ref_node->llist, &ctx->file_put_llist);
}
- spin_unlock(&data->lock);
+ spin_unlock_bh(&data->lock);

if (percpu_ref_is_dying(&data->refs))
delay = 0;
@@ -7520,9 +7520,9 @@ static int io_sqe_files_register(struct
}

file_data->node = ref_node;
- spin_lock(&file_data->lock);
+ spin_lock_bh(&file_data->lock);
list_add_tail(&ref_node->node, &file_data->ref_list);
- spin_unlock(&file_data->lock);
+ spin_unlock_bh(&file_data->lock);
percpu_ref_get(&file_data->refs);
return ret;
out_fput:
@@ -7679,10 +7679,10 @@ static int __io_sqe_files_update(struct

if (needs_switch) {
percpu_ref_kill(&data->node->refs);
- spin_lock(&data->lock);
+ spin_lock_bh(&data->lock);
list_add_tail(&ref_node->node, &data->ref_list);
data->node = ref_node;
- spin_unlock(&data->lock);
+ spin_unlock_bh(&data->lock);
percpu_ref_get(&ctx->file_data->refs);
} else
destroy_fixed_file_ref_node(ref_node);