From:   Thiago Rafael Becker <trbecker@gmail.com>
To:     linux-cifs@vger.kernel.org
Cc:     Steve French <sfrench@samba.org>, linux-kernel@vger.kernel.org,
        lsahlber@redhat.com, Thiago Rafael Becker <trbecker@gmail.com>
Subject: [PATCH 1/1] cifs: sanitize multiple delimiters in prepath
Date:   Wed, 15 Dec 2021 00:08:31 -0300
Message-Id: <20211215030831.24058-1-trbecker@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

mount.cifs can pass a device with multiple delimiters in it. This will
cause rename(2) to fail with ENOENT.

BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=2031200
Signed-off-by: Thiago Rafael Becker <trbecker@gmail.com>
---
 fs/cifs/fs_context.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/fs/cifs/fs_context.c b/fs/cifs/fs_context.c
index 6a179ae753c1..4ce8a7df3a02 100644
--- a/fs/cifs/fs_context.c
+++ b/fs/cifs/fs_context.c
@@ -434,6 +434,34 @@ int smb3_parse_opt(const char *options, const char *key, char **val)
 	return rc;
 }
 
+/*
+ * remove duplicate path delimiters. Windows is supposed to do that
+ * but there are some bugs that prevent rename from working if there are
+ * multiple delimiters.
+ */
+void sanitize_path(char *path) {
+        char *pos = path, last = *path;
+        unsigned int offset = 0;
+
+        while(*(++pos)) {
+                if ((*pos == '/' || *pos == '\\') && (last == '/' || last == '\\')) {
+                        offset++;
+                        continue;
+                }
+
+                last = *pos;
+                *(pos - offset) = *pos;
+        }
+
+        pos = pos - offset - 1;
+
+        /* At this point, there should be only zero or one delimiter at the end of the string */
+        if (*pos != '/' && *pos != '\\')
+                pos++;
+
+        *pos = '\0';
+}
+
 /*
  * Parse a devname into substrings and populate the ctx->UNC and ctx->prepath
  * fields with the result. Returns 0 on success and an error otherwise
@@ -497,6 +525,8 @@ smb3_parse_devname(const char *devname, struct smb3_fs_context *ctx)
 	if (!ctx->prepath)
 		return -ENOMEM;
 
+	sanitize_path(ctx->prepath);
+
 	return 0;
 }
 
-- 
2.31.1