linux-kernel - [PATCH] powerpc/sysdev: fix incorrect use to determine if list is empty

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Date:   Mon, 28 Feb 2022 15:24:33 +0100
From:   Jakob Koschel <jakobkoschel@...il.com>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     Jakob Koschel <jakobkoschel@...il.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Anton Vorontsov <avorontsov@...mvista.com>,
        Kumar Gala <galak@...nel.crashing.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: [PATCH] powerpc/sysdev: fix incorrect use to determine if list is empty

'gtm' will *always* be set by list_for_each_entry().
It is incorrect to assume that the iterator value will be NULL if the
list is empty.

Instead of checking the pointer it should be checked if
the list is empty.

Fixes: 83ff9dcf375c ("powerpc/sysdev: implement FSL GTM support")
Signed-off-by: Jakob Koschel <jakobkoschel@...il.com>
---
 arch/powerpc/sysdev/fsl_gtm.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/sysdev/fsl_gtm.c b/arch/powerpc/sysdev/fsl_gtm.c
index 8963eaffb1b7..39186ad6b3c3 100644
--- a/arch/powerpc/sysdev/fsl_gtm.c
+++ b/arch/powerpc/sysdev/fsl_gtm.c
@@ -86,7 +86,7 @@ static LIST_HEAD(gtms);
  */
 struct gtm_timer *gtm_get_timer16(void)
 {
-	struct gtm *gtm = NULL;
+	struct gtm *gtm;
 	int i;

 	list_for_each_entry(gtm, &gtms, list_node) {
@@ -103,7 +103,7 @@ struct gtm_timer *gtm_get_timer16(void)
 		spin_unlock_irq(&gtm->lock);
 	}

-	if (gtm)
+	if (!list_empty(&gtms))
 		return ERR_PTR(-EBUSY);
 	return ERR_PTR(-ENODEV);
 }

base-commit: 7ee022567bf9e2e0b3cd92461a2f4986ecc99673
--
2.25.1