linux-kernel - [PATCH AUTOSEL 5.15 12/17] scsi: lpfc: Avoid usage of list iterator variable after loop

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Message-Id: <20230320005521.1428820-12-sashal@kernel.org>
Date:   Sun, 19 Mar 2023 20:55:14 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Jakob Koschel <jkl820.git@...il.com>,
        Justin Tee <justin.tee@...adcom.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        Sasha Levin <sashal@...nel.org>, james.smart@...adcom.com,
        dick.kennedy@...adcom.com, jejb@...ux.ibm.com,
        linux-scsi@...r.kernel.org
Subject: [PATCH AUTOSEL 5.15 12/17] scsi: lpfc: Avoid usage of list iterator variable after loop

From: Jakob Koschel <jkl820.git@...il.com>

[ Upstream commit 2850b23e9f9ae3696e472d2883ea1b43aafa884e ]

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/ [1]
Signed-off-by: Jakob Koschel <jkl820.git@...il.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@...adcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/scsi/lpfc/lpfc_sli.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/scsi/lpfc/lpfc_sli.c b/drivers/scsi/lpfc/lpfc_sli.c
index 1f1d346adc038..30bc72324f068 100644
--- a/drivers/scsi/lpfc/lpfc_sli.c
+++ b/drivers/scsi/lpfc/lpfc_sli.c
@@ -22166,20 +22166,20 @@ 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;
 		}
 	}
-- 
2.39.2