From eefebf8877d3dda0b5b9bafa4cdcd8f99ac09e65 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= Date: Wed, 7 Jun 2023 19:28:48 +0200 Subject: [PATCH] fs: avoid empty option when generating legacy mount string MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit commit 62176420274db5b5127cd7a0083a9aeb461756ee 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 Fixes: 3e1aeb00e6d1 ("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 Signed-off-by: Greg Kroah-Hartman --- fs/fs_context.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/fs_context.c b/fs/fs_context.c index e492a83fa100..412712eb59ee 100644 --- a/fs/fs_context.c +++ b/fs/fs_context.c @@ -598,7 +598,8 @@ 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;