If smb2_create_link() is called with ReplaceIfExists set and the name
does exist then a deadlock will happen.
ksmbd_vfs_kern_path_locked() will return with success and the parent
directory will be locked. ksmbd_vfs_remove_file() will then remove the
file. ksmbd_vfs_link() will then be called while the parent is still
locked. It will try to lock the same parent and will deadlock.
This patch moves the ksmbd_vfs_kern_path_unlock() call to *before*
ksmbd_vfs_link() and then simplifies the code, removing the file_present
flag variable.
Signed-off-by: NeilBrown <neil@xxxxxxxxxx>
---
fs/smb/server/smb2pdu.c | 16 ++++------------
1 file changed, 4 insertions(+), 12 deletions(-)
diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c
index 0013052f5d98..2e98717a0268 100644
--- a/fs/smb/server/smb2pdu.c
+++ b/fs/smb/server/smb2pdu.c
@@ -6009,7 +6009,6 @@ static int smb2_create_link(struct ksmbd_work *work,
{
char *link_name = NULL, *target_name = NULL, *pathname = NULL;
struct path path, parent_path;
- bool file_present = false;
int rc;
if (buf_len < (u64)sizeof(struct smb2_file_link_info) +
@@ -6042,11 +6041,8 @@ static int smb2_create_link(struct ksmbd_work *work,
if (rc) {
if (rc != -ENOENT)
goto out;
- } else
- file_present = true;
-
- if (file_info->ReplaceIfExists) {
- if (file_present) {
+ } else {
+ if (file_info->ReplaceIfExists) {
rc = ksmbd_vfs_remove_file(work, &path);
if (rc) {
rc = -EINVAL;
@@ -6054,21 +6050,17 @@ static int smb2_create_link(struct ksmbd_work *work,
link_name);
goto out;
}
- }
- } else {
- if (file_present) {
+ } else {
rc = -EEXIST;
ksmbd_debug(SMB, "link already exists\n");
goto out;
}
+ ksmbd_vfs_kern_path_unlock(&parent_path, &path);
}
-
rc = ksmbd_vfs_link(work, target_name, link_name);
if (rc)
rc = -EINVAL;
out:
- if (file_present)
- ksmbd_vfs_kern_path_unlock(&parent_path, &path);
if (!IS_ERR(link_name))
kfree(link_name);
--
2.49.0
