Commit 00c796ee authored Mar 31, 2022 by Jakob Koschel Committed by Steve French Apr 04, 2022

cifs: remove check of list iterator against head past the loop body

When list_for_each_entry() completes the iteration over the whole list
without breaking the loop, the iterator value will be a bogus pointer
computed based on the head element.

While it is safe to use the pointer to determine if it was computed
based on the head element, either with list_entry_is_head() or
&pos->member == head, using the iterator variable after the loop should
be avoided.

In preparation to limit the scope of a list iterator to the list
traversal loop, use a dedicated pointer to point to the found element [1].

Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/

 [1]
Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Jakob Koschel <jakobkoschel@gmail.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

parent 687127c8

fs/cifs/smb2misc.c

+6 −4

Original line number	Diff line number	Diff line
		@@ -150,16 +150,18 @@ smb2_check_message(char buf, unsigned int len, struct TCP_Server_Info srvr)
		struct smb2_transform_hdr *thdr =
		(struct smb2_transform_hdr *)buf;
		struct cifs_ses *ses = NULL;
		struct cifs_ses *iter;

		/* decrypt frame now that it is completely read in */
		spin_lock(&cifs_tcp_ses_lock);
		list_for_each_entry(ses, &srvr->smb_ses_list, smb_ses_list) {
		if (ses->Suid == le64_to_cpu(thdr->SessionId))
		list_for_each_entry(iter, &srvr->smb_ses_list, smb_ses_list) {
		if (iter->Suid == le64_to_cpu(thdr->SessionId)) {
		ses = iter;
		break;
		}
		}
		spin_unlock(&cifs_tcp_ses_lock);
		if (list_entry_is_head(ses, &srvr->smb_ses_list,
		smb_ses_list)) {
		if (!ses) {
		cifs_dbg(VFS, "no decryption - session id not found\n");
		return 1;
		}