[RFC PATCH v4 5/5] btrfs: ioctl: don't free iov when -EAGAIN in uring encoded read

[Sidong Yang <sidong.yang@furiosa.ai>]

This patch fixes a bug on encoded_read. In btrfs_uring_encoded_read(),
btrfs_encoded_read could return -EAGAIN when receiving requests concurrently.
And data->iov goes to out_free and it freed and return -EAGAIN. io-uring
subsystem would call it again and it doesn't reset data. And data->iov
freed and iov_iter reference it. iov_iter would be used in
btrfs_uring_read_finished() and could be raise memory bug.

Signed-off-by: Sidong Yang <sidong.yang@furiosa.ai>
---
 fs/btrfs/ioctl.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index a7b52fd99059..02fa8dd1a3ce 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -4922,6 +4922,9 @@ static int btrfs_uring_encoded_read(struct io_uring_cmd *cmd, unsigned int issue
 
 	ret = btrfs_encoded_read(&kiocb, &data->iter, &data->args, &cached_state,
 				 &disk_bytenr, &disk_io_size);
+
+	if (ret == -EAGAIN)
+		goto out_acct;
 	if (ret < 0 && ret != -EIOCBQUEUED)
 		goto out_free;
 
-- 
2.43.0