[PATCH 5.15.y 05/11] ksmbd: don't allow O_TRUNC open on read-only share

Namjae Jeon
2024-01-21T14:31:17Z

[ Upstream commit d592a9158a112d419f341f035d18d02f8d232def ]

When file is changed using notepad on read-only share(read_only = yes in
ksmbd.conf), There is a problem where existing data is truncated.
notepad in windows try to O_TRUNC open(FILE_OVERWRITE_IF) and all data
in file is truncated. This patch don't allow O_TRUNC open on read-only
share and add KSMBD_TREE_CONN_FLAG_WRITABLE check in smb2_set_info().

Cc: stable@vger.kernel.org
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
---
fs/ksmbd/smb2pdu.c | 23 +++++++++--------------
1 file changed, 9 insertions(+), 14 deletions(-)

diff --git a/fs/ksmbd/smb2pdu.c b/fs/ksmbd/smb2pdu.c
index 5975a2bc471f..4d6663ab3d03 100644
--- a/fs/ksmbd/smb2pdu.c
+++ b/fs/ksmbd/smb2pdu.c
@@ -2969,7 +2969,7 @@ int smb2_open(struct ksmbd_work *work)
&may_flags);

if (!test_tree_conn_flag(tcon, KSMBD_TREE_CONN_FLAG_WRITABLE)) {
- if (open_flags & O_CREAT) {
+ if (open_flags & (O_CREAT | O_TRUNC)) {
ksmbd_debug(SMB,
"User does not have write permission\n");
rc = -EACCES;
@@ -5946,12 +5946,6 @@ static int smb2_set_info_file(struct ksmbd_work *work, struct ksmbd_file *fp,
}
case FILE_RENAME_INFORMATION:
{
- if (!test_tree_conn_flag(work->tcon, KSMBD_TREE_CONN_FLAG_WRITABLE)) {
- ksmbd_debug(SMB,
- "User does not have write permission\n");
- return -EACCES;
- }
-
if (buf_len < sizeof(struct smb2_file_rename_info))
return -EINVAL;

@@ -5971,12 +5965,6 @@ static int smb2_set_info_file(struct ksmbd_work *work, struct ksmbd_file *fp,
}
case FILE_DISPOSITION_INFORMATION:
{
- if (!test_tree_conn_flag(work->tcon, KSMBD_TREE_CONN_FLAG_WRITABLE)) {
- ksmbd_debug(SMB,
- "User does not have write permission\n");
- return -EACCES;
- }
-
if (buf_len < sizeof(struct smb2_file_disposition_info))
return -EINVAL;

@@ -6038,7 +6026,7 @@ int smb2_set_info(struct ksmbd_work *work)
{
struct smb2_set_info_req *req;
struct smb2_set_info_rsp *rsp;
- struct ksmbd_file *fp;
+ struct ksmbd_file *fp = NULL;
int rc = 0;
unsigned int id = KSMBD_NO_FID, pid = KSMBD_NO_FID;

@@ -6058,6 +6046,13 @@ int smb2_set_info(struct ksmbd_work *work)
rsp = smb2_get_msg(work->response_buf);
}

+ if (!test_tree_conn_flag(work->tcon, KSMBD_TREE_CONN_FLAG_WRITABLE)) {
+ ksmbd_debug(SMB, "User does not have write permission\n");
+ pr_err("User does not have write permission\n");
+ rc = -EACCES;
+ goto err_out;
+ }
+
if (!has_file_id(id)) {
id = req->VolatileFileId;
pid = req->PersistentFileId;
--
2.25.1