[PATCH] NFS: fix refcount leak in nfs_direct_write_schedule_iovec()

[PATCH] NFS: fix refcount leak in nfs_direct_write_schedule_iovec()

[WenTao Liang]

When nfs_direct_write_schedule_iovec() fails to start any write
operations (requested_bytes == 0), it bails out after calling
inode_dio_end() but before releasing the dreq->io_count reference
that was unconditionally acquired by get_dreq().  The normal
success path balances that via put_dreq(), which decrements the
io_count and eventually calls nfs_direct_write_complete().  The
leaked reference prevents proper cleanup of the direct write request.

Add the missing put_dreq() in the early exit path before calling
nfs_direct_req_release().

Cc: stable@vger.kernel.org
Fixes: 65caafd0d214 ("SUNRPC reverting d03727b248d0 ("NFSv4 fix CLOSE not waiting for direct IO compeletion")")
Signed-off-by: WenTao Liang <vulab@iscas.ac.cn>
---
 fs/nfs/direct.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index 41a6cabb0592..99bd72a4601c 100644
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -956,6 +956,7 @@ static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq,
 	 */
 	if (requested_bytes == 0) {
 		inode_dio_end(inode);
+		put_dreq(dreq);
 		nfs_direct_req_release(dreq);
 		return result < 0 ? result : -EIO;
 	}
-- 
2.50.1 (Apple Git-155)

Re: [PATCH] NFS: fix refcount leak in nfs_direct_write_schedule_iovec()

[Trond Myklebust]

On Thu, 2026-06-11 at 23:03 +0800, WenTao Liang wrote:
> When nfs_direct_write_schedule_iovec() fails to start any write
> operations (requested_bytes == 0), it bails out after calling
> inode_dio_end() but before releasing the dreq->io_count reference
> that was unconditionally acquired by get_dreq().  The normal
> success path balances that via put_dreq(), which decrements the
> io_count and eventually calls nfs_direct_write_complete().  The
> leaked reference prevents proper cleanup of the direct write request.

Again, I'd like you to explain this claim that somehow io_count is
preventing cleanup of the request. Neither nfs_file_direct_write nor
nfs_direct_req_release care about its value.

> 
> Add the missing put_dreq() in the early exit path before calling
> nfs_direct_req_release().
> 
> Cc: stable@vger.kernel.org
> Fixes: 65caafd0d214 ("SUNRPC reverting d03727b248d0 ("NFSv4 fix CLOSE
> not waiting for direct IO compeletion")")
> Signed-off-by: WenTao Liang <vulab@iscas.ac.cn>
> ---
>  fs/nfs/direct.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
> index 41a6cabb0592..99bd72a4601c 100644
> --- a/fs/nfs/direct.c
> +++ b/fs/nfs/direct.c
> @@ -956,6 +956,7 @@ static ssize_t
> nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq,
>  	 */
>  	if (requested_bytes == 0) {
>  		inode_dio_end(inode);
> +		put_dreq(dreq);
>  		nfs_direct_req_release(dreq);
>  		return result < 0 ? result : -EIO;
>  	}

-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trondmy@kernel.org, trond.myklebust@hammerspace.com