Re: [PATCH] Add full_path_type arg to cifs_build_path_to_root()

[Aurélien Aptel <aaptel@xxxxxxxx>]

On Wed, 20 Apr 2016 18:16:34 +0200 Aurélien Aptel <aaptel@xxxxxxxx>
wrote:
> There are 2 ways to fix this:
> - never prefix an UNC path, even when using a DFS link i.e. remove all
>   code dealing with DFS from cifs_build_path_to_root)
> - add a new arg to decide the behaviour of cifs_build_path_to_root().

We have 2 customers reporting a bug involving this problem
internally at SUSE. I'm letting you know the first solution (patch
attached) will be in the next update of SUSE (SLE) kernels.

-- 
Aurélien Aptel / SUSE Labs Samba Team
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Nürnberg)

From df54ca09437a11438e1ec880c80c92e93ba98d71 Mon Sep 17 00:00:00 2001
From: Aurelien Aptel <aaptel@xxxxxxxx>
Date: Tue, 26 Apr 2016 17:59:06 +0200
Subject: [PATCH] fs/cifs: remove DFS handling from cifs_build_path_to_root()

This function is called from:
    - cifs_mount()
    - cifs_get_root()

The later expects a full path from the root, even in the presence of
a DFS link.

e.g. in the case of a DFS link like

    //A/shareA/link -> //B/shareB/sub/dir/

When doing a "cd link", cifs_get_root() was getting

    "//B/shareB//sub/dir"

Instead of

    "/sub/dir"

Resulting in

    sh: cd: link: No such file or directory

Thanks to Josef Cejka <jcejka@xxxxxxxx> for finding the bug&fix.

Reported-by: Fons Jongh <fons.dejongh@xxxxxxxxxxxxxx>
Signed-off-by: Aurelien Aptel <aaptel@xxxxxxxx>
---
 fs/cifs/dir.c | 23 ++++-------------------
 1 file changed, 4 insertions(+), 19 deletions(-)

diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index fb0903f..05f7480 100644
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -49,31 +49,16 @@ char *
 cifs_build_path_to_root(struct smb_vol *vol, struct cifs_sb_info *cifs_sb,
 			struct cifs_tcon *tcon)
 {
-	int pplen = vol->prepath ? strlen(vol->prepath) + 1 : 0;
-	int dfsplen;
+	int pplen = vol->prepath ? strlen(vol->prepath) : 0;
 	char *full_path = NULL;
 
-	/* if no prefix path, simply set path to the root of share to "" */
-	if (pplen == 0) {
-		full_path = kzalloc(1, GFP_KERNEL);
-		return full_path;
-	}
-
-	if (tcon->Flags & SMB_SHARE_IS_IN_DFS)
-		dfsplen = strnlen(tcon->treeName, MAX_TREE_SIZE + 1);
-	else
-		dfsplen = 0;
-
-	full_path = kmalloc(dfsplen + pplen + 1, GFP_KERNEL);
+	full_path = kmalloc(pplen + 1, GFP_KERNEL);
 	if (full_path == NULL)
 		return full_path;
 
-	if (dfsplen)
-		strncpy(full_path, tcon->treeName, dfsplen);
-	full_path[dfsplen] = CIFS_DIR_SEP(cifs_sb);
-	strncpy(full_path + dfsplen + 1, vol->prepath, pplen);
+	strncpy(full_path, vol->prepath, pplen);
 	convert_delimiter(full_path, CIFS_DIR_SEP(cifs_sb));
-	full_path[dfsplen + pplen] = 0; /* add trailing null */
+	full_path[pplen] = 0; /* add trailing null */
 	return full_path;
 }
 
-- 
2.1.4

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