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

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Message-ID: <20250317135742.4331-6-sidong.yang@furiosa.ai>
Date: Mon, 17 Mar 2025 13:57:42 +0000
From: Sidong Yang <sidong.yang@...iosa.ai>
To: Josef Bacik <josef@...icpanda.com>,
	David Sterba <dsterba@...e.com>,
	Jens Axboe <axboe@...nel.dk>,
	Pavel Begunkov <asml.silence@...il.com>
Cc: linux-btrfs@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	io-uring@...r.kernel.org,
	Sidong Yang <sidong.yang@...iosa.ai>
Subject: [RFC PATCH v4 5/5] btrfs: ioctl: don't free iov when -EAGAIN in uring encoded read

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@...iosa.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