scsi: lpfc: Avoid usage of list iterator variable after loop

If the &epd_pool->list is empty when executing
lpfc_get_io_buf_from_expedite_pool() the function would return an invalid
pointer. Even in the case if the list is guaranteed to be populated, the
iterator variable should not be used after the loop to be more robust for
future changes.

Linus proposed to avoid any use of the list iterator variable after the
loop, in the attempt to move the list iterator variable declaration into
the macro to avoid any potential misuse after the loop [1].

Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/
Signed-off-by: Jakob Koschel <jkl820.git@gmail.com>
Link: https://lore.kernel.org/r/20230301-scsi-lpfc-avoid-list-iterator-after-loop-v1-1-325578ae7561@gmail.com
Reviewed-by: Justin Tee <justin.tee@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/lpfc/lpfc_sli.c b/drivers/scsi/lpfc/lpfc_sli.c
index c5ad46fdde81733a5ae834f695b85204e50e804a..cf630aa6734eb60fb9c9ce9de53bc3fe411e1719 100644 (file)
--- a/drivers/scsi/lpfc/lpfc_sli.c
+++ b/drivers/scsi/lpfc/lpfc_sli.c
@@ -21899,20 +21899,20 @@ lpfc_get_io_buf_from_private_pool(struct lpfc_hba *phba,
 static struct lpfc_io_buf *
 lpfc_get_io_buf_from_expedite_pool(struct lpfc_hba *phba)
 {
-       struct lpfc_io_buf *lpfc_ncmd;
+       struct lpfc_io_buf *lpfc_ncmd = NULL, *iter;
        struct lpfc_io_buf *lpfc_ncmd_next;
        unsigned long iflag;
        struct lpfc_epd_pool *epd_pool;
 
        epd_pool = &phba->epd_pool;
-       lpfc_ncmd = NULL;
 
        spin_lock_irqsave(&epd_pool->lock, iflag);
        if (epd_pool->count > 0) {
-               list_for_each_entry_safe(lpfc_ncmd, lpfc_ncmd_next,
+               list_for_each_entry_safe(iter, lpfc_ncmd_next,
                                         &epd_pool->list, list) {
-                       list_del(&lpfc_ncmd->list);
+                       list_del(&iter->list);
                        epd_pool->count--;
+                       lpfc_ncmd = iter;
                        break;
                }
        }