[PATCH v3 4/5] btrfs: don't stash uring encoded data across -EAGAIN

Returning -EAGAIN while leaving btrfs_uring_encoded_data in the cmd PDU
leaks if the request is cancelled or the ring exits before reissue.
io_uring does not free driver PDU allocations on cleanup.

Write: io_queue_sqe() always issues with IO_URING_F_NONBLOCK first, so
return -EAGAIN before allocating and free data on every exit.

Read: free on nowait -EAGAIN too; only -EIOCBQUEUED keeps the
allocation for btrfs_uring_read_finished().

Fixes: 34310c442e17 ("btrfs: add io_uring command for encoded reads (ENCODED_READ ioctl)")
Fixes: e32dcdb0af9f ("btrfs: add io_uring interface for encoded writes")
Signed-off-by: Yang Xiuwei <[email protected]>
---
 fs/btrfs/ioctl.c | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 8f598b134bc1..a3ca15901cde 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -4785,7 +4785,7 @@ 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;
+		goto out_free;
 	if (ret < 0 && ret != -EIOCBQUEUED)
 		goto out_free;
 
@@ -4827,8 +4827,10 @@ static int btrfs_uring_encoded_read(struct io_uring_cmd *cmd, unsigned int issue
 		add_rchar(current, ret);
 	inc_syscr(current);
 
-	if (ret != -EIOCBQUEUED && ret != -EAGAIN)
+	if (ret != -EIOCBQUEUED) {
 		kfree(data);
+		bc->data = NULL;
+	}
 
 	return ret;
 }
@@ -4857,6 +4859,11 @@ static int btrfs_uring_encoded_write(struct io_uring_cmd *cmd, unsigned int issu
 		goto out_acct;
 	}
 
+	if (issue_flags & IO_URING_F_NONBLOCK) {
+		ret = -EAGAIN;
+		goto out_acct;
+	}
+
 	if (!data) {
 		data = kzalloc_obj(*data, GFP_NOFS);
 		if (!data) {
@@ -4925,11 +4932,6 @@ static int btrfs_uring_encoded_write(struct io_uring_cmd *cmd, unsigned int issu
 		}
 	}
 
-	if (issue_flags & IO_URING_F_NONBLOCK) {
-		ret = -EAGAIN;
-		goto out_acct;
-	}
-
 	pos = data->args.offset;
 	ret = rw_verify_area(WRITE, file, &pos, data->args.len);
 	if (ret < 0)
@@ -4955,8 +4957,8 @@ static int btrfs_uring_encoded_write(struct io_uring_cmd *cmd, unsigned int issu
 		add_wchar(current, ret);
 	inc_syscw(current);
 
-	if (ret != -EAGAIN)
-		kfree(data);
+	kfree(data);
+	bc->data = NULL;
 	return ret;
 }
 
-- 
2.25.1