fs: avoid empty option when generating legacy mount string

commit 6217642027 upstream.

As each option string fragment is always prepended with a comma it would
happen that the whole string always starts with a comma. This could be
interpreted by filesystem drivers as an empty option and may produce
errors.

For example the NTFS driver from ntfs.ko behaves like this and fails
when mounted via the new API.

Link: https://github.com/util-linux/util-linux/issues/2298
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Fixes: 3e1aeb00e6 ("vfs: Implement a filesystem superblock creation/configuration context")
Cc: stable@vger.kernel.org
Message-Id: <20230607-fs-empty-option-v1-1-20c8dbf4671b@weissschuh.net>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Thomas Weißschuh 2023-06-07 19:28:48 +02:00 committed by Greg Kroah-Hartman
parent 79b9ab357b
commit dd15d1c5c2

View File

@ -561,7 +561,8 @@ static int legacy_parse_param(struct fs_context *fc, struct fs_parameter *param)
return -ENOMEM;
}
ctx->legacy_data[size++] = ',';
if (size)
ctx->legacy_data[size++] = ',';
len = strlen(param->key);
memcpy(ctx->legacy_data + size, param->key, len);
size += len;