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From:   Bartosz Golaszewski <brgl@bgdev.pl>
To:     Jonathan Corbet <corbet@lwn.net>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J . Wysocki" <rafael@kernel.org>,
        Guenter Roeck <linux@roeck-us.net>,
        Jean Delvare <jdelvare@suse.com>
Cc:     linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-hwmon@vger.kernel.org,
        Bartosz Golaszewski <bgolaszewski@baylibre.com>
Subject: [PATCH v2 4/6] devres: handle zero size in devm_kmalloc()
Date:   Mon, 29 Jun 2020 08:50:06 +0200
Message-Id: <20200629065008.27620-5-brgl@bgdev.pl>
In-Reply-To: <20200629065008.27620-1-brgl@bgdev.pl>
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From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

Make devm_kmalloc() behave similarly to non-managed kmalloc(): return
ZERO_SIZE_PTR when requested size is 0. Update devm_kfree() to handle
this case.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
 drivers/base/devres.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/base/devres.c b/drivers/base/devres.c
index 1df1fb10b2d9..ed615d3b9cf1 100644
--- a/drivers/base/devres.c
+++ b/drivers/base/devres.c
@@ -819,6 +819,9 @@ void *devm_kmalloc(struct device *dev, size_t size, gfp_t gfp)
 {
 	struct devres *dr;
 
+	if (unlikely(!size))
+		return ZERO_SIZE_PTR;
+
 	/* use raw alloc_dr for kmalloc caller tracing */
 	dr = alloc_dr(devm_kmalloc_release, size, gfp, dev_to_node(dev));
 	if (unlikely(!dr))
@@ -950,10 +953,10 @@ void devm_kfree(struct device *dev, const void *p)
 	int rc;
 
 	/*
-	 * Special case: pointer to a string in .rodata returned by
-	 * devm_kstrdup_const().
+	 * Special cases: pointer to a string in .rodata returned by
+	 * devm_kstrdup_const() or NULL/ZERO ptr.
 	 */
-	if (unlikely(is_kernel_rodata((unsigned long)p)))
+	if (unlikely(is_kernel_rodata((unsigned long)p) || ZERO_OR_NULL_PTR(p)))
 		return;
 
 	rc = devres_destroy(dev, devm_kmalloc_release,
-- 
2.26.1