linux-kernel - [PATCH 2/2] 9p: Fix writeback fid incorrectly being attached to dentry

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Date:   Thu, 19 Nov 2020 17:06:52 +0100
From:   Dominique Martinet <asmadeus@...ewreck.org>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Jianyong Wu <jianyong.wu@....com>, lucho@...kov.net,
        justin.he@....com, ericvh@...il.com, qemu_oss@...debyte.com,
        groug@...d.org, linux-kernel@...r.kernel.org,
        v9fs-developer@...ts.sourceforge.net,
        Dominique Martinet <asmadeus@...ewreck.org>
Subject: [PATCH 2/2] 9p: Fix writeback fid incorrectly being attached to dentry

v9fs_dir_release needs fid->ilist to have been initialized for filp's
fid, not the inode's writeback fid's.

With refcounting this can be improved on later but this appears to fix
null deref issues.

Fixes: xxx ("fs/9p: track open fids")
Signed-off-by: Dominique Martinet <asmadeus@...ewreck.org>
---
(note: fixes tag can't be filled here, will be corrected later)
 fs/9p/vfs_file.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
index b0ef225cecd0..c5e49c88688d 100644
--- a/fs/9p/vfs_file.c
+++ b/fs/9p/vfs_file.c
@@ -46,7 +46,7 @@ int v9fs_file_open(struct inode *inode, struct file *file)
 	int err;
 	struct v9fs_inode *v9inode;
 	struct v9fs_session_info *v9ses;
-	struct p9_fid *fid;
+	struct p9_fid *fid, *writeback_fid;
 	int omode;
 
 	p9_debug(P9_DEBUG_VFS, "inode: %p file: %p\n", inode, file);
@@ -85,13 +85,13 @@ int v9fs_file_open(struct inode *inode, struct file *file)
 		 * because we want write after unlink usecase
 		 * to work.
 		 */
-		fid = v9fs_writeback_fid(file_dentry(file));
+		writeback_fid = v9fs_writeback_fid(file_dentry(file));
 		if (IS_ERR(fid)) {
 			err = PTR_ERR(fid);
 			mutex_unlock(&v9inode->v_mutex);
 			goto out_error;
 		}
-		v9inode->writeback_fid = (void *) fid;
+		v9inode->writeback_fid = (void *) writeback_fid;
 	}
 	mutex_unlock(&v9inode->v_mutex);
 	if (v9ses->cache == CACHE_LOOSE || v9ses->cache == CACHE_FSCACHE)
-- 
2.28.0