6.1-stable review patch. If anyone has any objections, please let me know.
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From: NeilBrown neil@brown.name
[ Upstream commit d5fc1400a34b4ea5e8f2ce296ea12bf8c8421694 ]
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@brown.name Acked-by: Namjae Jeon linkinjeon@kernel.org Signed-off-by: Steve French stfrench@microsoft.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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 3e2cd22fb2bd..7943b2ee2a76 100644 --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -5648,7 +5648,6 @@ 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) + @@ -5681,11 +5680,8 @@ 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; @@ -5693,21 +5689,17 @@ 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);