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Thu, 03 Oct 2024 06:14:01 -0700 (PDT) Received: from prasmi.home ([2a00:23c8:2500:a01:2595:4364:d152:dff3]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a99102858b0sm84721666b.40.2024.10.03.06.14.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Oct 2024 06:14:00 -0700 (PDT) From: Prabhakar X-Google-Original-From: Prabhakar To: Linus Walleij , Bartosz Golaszewski , Geert Uytterhoeven Cc: linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org, linux-renesas-soc@vger.kernel.org, Prabhakar , Biju Das , Fabrizio Castro , Lad Prabhakar Subject: [PATCH] gpiolib: Fix potential NULL pointer dereference in gpiod_get_label() Date: Thu, 3 Oct 2024 14:13:51 +0100 Message-ID: <20241003131351.472015-1-prabhakar.mahadev-lad.rj@bp.renesas.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-gpio@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Lad Prabhakar In `gpiod_get_label()`, it is possible that `srcu_dereference_check()` may return a NULL pointer, leading to a scenario where `label->str` is accessed without verifying if `label` itself is NULL. This patch adds a proper NULL check for `label` before accessing `label->str`. The check for `label->str != NULL` is removed because `label->str` can never be NULL if `label` is not NULL. This fixes the issue where the label name was being printed as `(efault)` when dumping the sysfs GPIO file when `label == NULL`. Signed-off-by: Lad Prabhakar Reviewed-by: Geert Uytterhoeven --- Output before this patch: root@smarc-rzg2l:~# cat /sys/kernel/debug/gpio | grep P2_1 gpio-529 (P2_1 |(efault) ) in hi IRQ Output after this patch: root@smarc-rzg2l:~# cat /sys/kernel/debug/gpio | grep P2_1 gpio-529 (P2_1 |interrupt ) in hi IRQ --- drivers/gpio/gpiolib.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index c6afbf434366..d5952ab7752c 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -114,12 +114,12 @@ const char *gpiod_get_label(struct gpio_desc *desc) srcu_read_lock_held(&desc->gdev->desc_srcu)); if (test_bit(FLAG_USED_AS_IRQ, &flags)) - return label->str ?: "interrupt"; + return label ? label->str : "interrupt"; if (!test_bit(FLAG_REQUESTED, &flags)) return NULL; - return label->str; + return label ? label->str : NULL; } static void desc_free_label(struct rcu_head *rh)