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Subject[PATCH 2/2] cifs: remove check of list iterator against head past the loop body
Date
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]
Signed-off-by: Jakob Koschel <jakobkoschel@gmail.com>
---
fs/cifs/smb2misc.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/fs/cifs/smb2misc.c b/fs/cifs/smb2misc.c
index b25623e3fe3d..2d862291fab9 100644
--- a/fs/cifs/smb2misc.c
+++ b/fs/cifs/smb2misc.c
@@ -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;
}
--
2.25.1
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