linux-ext4 - [PATCH 12/13] cifs_get_link(): bail out in unsafe case

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Date: Sun,  4 Feb 2024 02:17:38 +0000
From: Al Viro <viro@...iv.linux.org.uk>
To: linux-fsdevel@...r.kernel.org
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
	Christian Brauner <brauner@...nel.org>,
	linux-ext4@...r.kernel.org,
	linux-nfs@...r.kernel.org,
	Miklos Szeredi <miklos@...redi.hu>,
	linux-cifs@...r.kernel.org
Subject: [PATCH 12/13] cifs_get_link(): bail out in unsafe case

->d_revalidate() bails out there, anyway.  It's not enough
to prevent getting into ->get_link() in RCU mode, but that
could happen only in a very contrieved setup.  Not worth
trying to do anything fancy here unless ->d_revalidate()
stops kicking out of RCU mode at least in some cases.

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 fs/smb/client/cifsfs.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/smb/client/cifsfs.c b/fs/smb/client/cifsfs.c
index e902de4e475a..630e74628dfe 100644
--- a/fs/smb/client/cifsfs.c
+++ b/fs/smb/client/cifsfs.c
@@ -1172,6 +1172,9 @@ const char *cifs_get_link(struct dentry *dentry, struct inode *inode,
 {
 	char *target_path;
 
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+
 	target_path = kmalloc(PATH_MAX, GFP_KERNEL);
 	if (!target_path)
 		return ERR_PTR(-ENOMEM);
-- 
2.39.2