diff mbox series

wifi: ipw2x00: refactor to use kstrtoul

Message ID 20230802-wifi-ipw2x00-refactor-v1-1-6047659410d4@google.com (mailing list archive)
State Changes Requested
Delegated to: Kalle Valo
Headers show
Series wifi: ipw2x00: refactor to use kstrtoul | expand

Commit Message

Justin Stitt Aug. 2, 2023, 12:51 a.m. UTC 
The current implementation seems to reinvent what `kstrtoul` already does
in terms of functionality and error handling. Remove uses of `simple_strtoul()`
in favor of `kstrtoul()`.

There is the following note at `lib/vsprintf.c:simple_strtoull()` which
further backs this change:
| * This function has caveats. Please use kstrtoull (or kstrtoul) instead.

And here, simple_str* are explicitly deprecated [3].

This patch also removes an instance of the deprecated `strncpy` which helps [2].

Link: https://lore.kernel.org/all/202308011602.3CC1C0244C@keescook/ [1]
Link: https://github.com/KSPP/linux/issues/90 [2]
Link: https://docs.kernel.org/process/deprecated.html#simple-strtol-simple-strtoll-simple-strtoul-simple-strtoull [3]
Cc: linux-hardening@vger.kernel.org
Suggested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Justin Stitt <justinstitt@google.com>
---


Link: https://lore.kernel.org/all/20230801-drivers-net-wireless-intel-ipw2x00-v1-1-ffd185c91292@google.com/
---
 drivers/net/wireless/intel/ipw2x00/ipw2200.c | 43 +++++++++-------------------
 1 file changed, 14 insertions(+), 29 deletions(-)


---
base-commit: 5d0c230f1de8c7515b6567d9afba1f196fb4e2f4
change-id: 20230801-wifi-ipw2x00-refactor-fa6deb6c67ea

Best regards,
--
Justin Stitt <justinstitt@google.com>

Comments

Kees Cook Aug. 2, 2023, 1:16 a.m. UTC | #1 
On August 1, 2023 5:51:59 PM PDT, Justin Stitt <justinstitt@google.com> wrote:
>The current implementation seems to reinvent what `kstrtoul` already does
>in terms of functionality and error handling. Remove uses of `simple_strtoul()`
>in favor of `kstrtoul()`.
>
>There is the following note at `lib/vsprintf.c:simple_strtoull()` which
>further backs this change:
>| * This function has caveats. Please use kstrtoull (or kstrtoul) instead.
>
>And here, simple_str* are explicitly deprecated [3].
>
>This patch also removes an instance of the deprecated `strncpy` which helps [2].
>
>Link: https://lore.kernel.org/all/202308011602.3CC1C0244C@keescook/ [1]
>Link: https://github.com/KSPP/linux/issues/90 [2]
>Link: https://docs.kernel.org/process/deprecated.html#simple-strtol-simple-strtoll-simple-strtoul-simple-strtoull [3]
>Cc: linux-hardening@vger.kernel.org
>Suggested-by: Kees Cook <keescook@chromium.org>
>Signed-off-by: Justin Stitt <justinstitt@google.com>
>---
>
>
>Link: https://lore.kernel.org/all/20230801-drivers-net-wireless-intel-ipw2x00-v1-1-ffd185c91292@google.com/
>---
> drivers/net/wireless/intel/ipw2x00/ipw2200.c | 43 +++++++++-------------------
> 1 file changed, 14 insertions(+), 29 deletions(-)
>
>diff --git a/drivers/net/wireless/intel/ipw2x00/ipw2200.c b/drivers/net/wireless/intel/ipw2x00/ipw2200.c
>index dfe0f74369e6..ac10633f593e 100644
>--- a/drivers/net/wireless/intel/ipw2x00/ipw2200.c
>+++ b/drivers/net/wireless/intel/ipw2x00/ipw2200.c
>@@ -1176,23 +1176,20 @@ static ssize_t debug_level_show(struct device_driver *d, char *buf)
> static ssize_t debug_level_store(struct device_driver *d, const char *buf,
> 				 size_t count)
> {
>-	char *p = (char *)buf;
>-	u32 val;
>+	unsigned long *val = NULL;
> 
>-	if (p[1] == 'x' || p[1] == 'X' || p[0] == 'x' || p[0] == 'X') {
>-		p++;
>-		if (p[0] == 'x' || p[0] == 'X')
>-			p++;
>-		val = simple_strtoul(p, &p, 16);
>-	} else
>-		val = simple_strtoul(p, &p, 10);
>-	if (p == buf)
>+	int result = kstrtoul(buf, 0, val);

kstrtoul needs somewhere to write the value, so val need to be actually unsigned long, and a pointer passed to that:

unsigned long val;
...
... kstrtoul(but, 0, &val);

But otherwise, yeah, this looks like the right direction to me.

>+
>+	if (result == -EINVAL)
> 		printk(KERN_INFO DRV_NAME
> 		       ": %s is not in hex or decimal form.\n", buf);
>+	else if (result == -ERANGE)
>+		printk(KERN_INFO DRV_NAME
>+			 ": %s has overflowed.\n", buf);
> 	else
>-		ipw_debug_level = val;
>+		ipw_debug_level = *val;
> 
>-	return strnlen(buf, count);
>+	return count;.

It might be worth mentioning this return value change, but I think it's correct: we're communicating how much was consumed (we consumed it all). When the return value != count, this function may be called again with the "rest" of the input. As this is a sysfs interface, that kind of behavior is very rare bordering on actively unwanted. :) So, I think these should either return a negative error or count.

-Kees

> }
> static DRIVER_ATTR_RW(debug_level);
> 
>@@ -1461,33 +1458,21 @@ static ssize_t scan_age_store(struct device *d, struct device_attribute *attr,
> {
> 	struct ipw_priv *priv = dev_get_drvdata(d);
> 	struct net_device *dev = priv->net_dev;
>-	char buffer[] = "00000000";
>-	unsigned long len =
>-	    (sizeof(buffer) - 1) > count ? count : sizeof(buffer) - 1;
>-	unsigned long val;
>-	char *p = buffer;
> 
> 	IPW_DEBUG_INFO("enter\n");
> 
>-	strncpy(buffer, buf, len);
>-	buffer[len] = 0;
>+	unsigned long *val = NULL;
>+	int result = kstrtoul(buf, 0, val);
> 
>-	if (p[1] == 'x' || p[1] == 'X' || p[0] == 'x' || p[0] == 'X') {
>-		p++;
>-		if (p[0] == 'x' || p[0] == 'X')
>-			p++;
>-		val = simple_strtoul(p, &p, 16);
>-	} else
>-		val = simple_strtoul(p, &p, 10);
>-	if (p == buffer) {
>+	if (result == -EINVAL || result == -ERANGE) {
> 		IPW_DEBUG_INFO("%s: user supplied invalid value.\n", dev->name);
> 	} else {
>-		priv->ieee->scan_age = val;
>+		priv->ieee->scan_age = *val;
> 		IPW_DEBUG_INFO("set scan_age = %u\n", priv->ieee->scan_age);
> 	}
> 
> 	IPW_DEBUG_INFO("exit\n");
>-	return len;
>+	return count;
> }
> 
> static DEVICE_ATTR_RW(scan_age);
>
>---
>base-commit: 5d0c230f1de8c7515b6567d9afba1f196fb4e2f4
>change-id: 20230801-wifi-ipw2x00-refactor-fa6deb6c67ea
>
>Best regards,
>--
>Justin Stitt <justinstitt@google.com>
>
Justin Stitt Aug. 2, 2023, 1:25 a.m. UTC | #2 
On Tue, Aug 1, 2023 at 6:16 PM Kees Cook <kees@kernel.org> wrote:
>
> On August 1, 2023 5:51:59 PM PDT, Justin Stitt <justinstitt@google.com> wrote:
> >The current implementation seems to reinvent what `kstrtoul` already does
> >in terms of functionality and error handling. Remove uses of `simple_strtoul()`
> >in favor of `kstrtoul()`.
> >
> >There is the following note at `lib/vsprintf.c:simple_strtoull()` which
> >further backs this change:
> >| * This function has caveats. Please use kstrtoull (or kstrtoul) instead.
> >
> >And here, simple_str* are explicitly deprecated [3].
> >
> >This patch also removes an instance of the deprecated `strncpy` which helps [2].
> >
> >Link: https://lore.kernel.org/all/202308011602.3CC1C0244C@keescook/ [1]
> >Link: https://github.com/KSPP/linux/issues/90 [2]
> >Link: https://docs.kernel.org/process/deprecated.html#simple-strtol-simple-strtoll-simple-strtoul-simple-strtoull [3]
> >Cc: linux-hardening@vger.kernel.org
> >Suggested-by: Kees Cook <keescook@chromium.org>
> >Signed-off-by: Justin Stitt <justinstitt@google.com>
> >---
> >
> >
> >Link: https://lore.kernel.org/all/20230801-drivers-net-wireless-intel-ipw2x00-v1-1-ffd185c91292@google.com/
> >---
> > drivers/net/wireless/intel/ipw2x00/ipw2200.c | 43 +++++++++-------------------
> > 1 file changed, 14 insertions(+), 29 deletions(-)
> >
> >diff --git a/drivers/net/wireless/intel/ipw2x00/ipw2200.c b/drivers/net/wireless/intel/ipw2x00/ipw2200.c
> >index dfe0f74369e6..ac10633f593e 100644
> >--- a/drivers/net/wireless/intel/ipw2x00/ipw2200.c
> >+++ b/drivers/net/wireless/intel/ipw2x00/ipw2200.c
> >@@ -1176,23 +1176,20 @@ static ssize_t debug_level_show(struct device_driver *d, char *buf)
> > static ssize_t debug_level_store(struct device_driver *d, const char *buf,
> >                                size_t count)
> > {
> >-      char *p = (char *)buf;
> >-      u32 val;
> >+      unsigned long *val = NULL;
> >
> >-      if (p[1] == 'x' || p[1] == 'X' || p[0] == 'x' || p[0] == 'X') {
> >-              p++;
> >-              if (p[0] == 'x' || p[0] == 'X')
> >-                      p++;
> >-              val = simple_strtoul(p, &p, 16);
> >-      } else
> >-              val = simple_strtoul(p, &p, 10);
> >-      if (p == buf)
> >+      int result = kstrtoul(buf, 0, val);
>
> kstrtoul needs somewhere to write the value, so val need to be actually unsigned long, and a pointer passed to that:
>
> unsigned long val;
> ...
> ... kstrtoul(but, 0, &val);
>
> But otherwise, yeah, this looks like the right direction to me.
>
> >+
> >+      if (result == -EINVAL)
> >               printk(KERN_INFO DRV_NAME
> >                      ": %s is not in hex or decimal form.\n", buf);
> >+      else if (result == -ERANGE)
> >+              printk(KERN_INFO DRV_NAME
> >+                       ": %s has overflowed.\n", buf);
> >       else
> >-              ipw_debug_level = val;
> >+              ipw_debug_level = *val;
> >
> >-      return strnlen(buf, count);
> >+      return count;.
>
> It might be worth mentioning this return value change, but I think it's correct: we're communicating how much was consumed (we consumed it all). When the return value != count, this function may be called again with the "rest" of the input. As this is a sysfs interface, that kind of behavior is very rare bordering on actively unwanted. :) So, I think these should either return a negative error or count.
>
> -Kees
>
> > }
> > static DRIVER_ATTR_RW(debug_level);
> >
> >@@ -1461,33 +1458,21 @@ static ssize_t scan_age_store(struct device *d, struct device_attribute *attr,
> > {
> >       struct ipw_priv *priv = dev_get_drvdata(d);
> >       struct net_device *dev = priv->net_dev;
> >-      char buffer[] = "00000000";
> >-      unsigned long len =
> >-          (sizeof(buffer) - 1) > count ? count : sizeof(buffer) - 1;
> >-      unsigned long val;
> >-      char *p = buffer;
> >
> >       IPW_DEBUG_INFO("enter\n");
> >
> >-      strncpy(buffer, buf, len);
> >-      buffer[len] = 0;
> >+      unsigned long *val = NULL;
> >+      int result = kstrtoul(buf, 0, val);
> >
> >-      if (p[1] == 'x' || p[1] == 'X' || p[0] == 'x' || p[0] == 'X') {
> >-              p++;
> >-              if (p[0] == 'x' || p[0] == 'X')
> >-                      p++;
> >-              val = simple_strtoul(p, &p, 16);
> >-      } else
> >-              val = simple_strtoul(p, &p, 10);
> >-      if (p == buffer) {
> >+      if (result == -EINVAL || result == -ERANGE) {
> >               IPW_DEBUG_INFO("%s: user supplied invalid value.\n", dev->name);
> >       } else {
> >-              priv->ieee->scan_age = val;
> >+              priv->ieee->scan_age = *val;
> >               IPW_DEBUG_INFO("set scan_age = %u\n", priv->ieee->scan_age);
> >       }
> >
> >       IPW_DEBUG_INFO("exit\n");
> >-      return len;
> >+      return count;
> > }
> >
> > static DEVICE_ATTR_RW(scan_age);
> >
> >---
> >base-commit: 5d0c230f1de8c7515b6567d9afba1f196fb4e2f4
> >change-id: 20230801-wifi-ipw2x00-refactor-fa6deb6c67ea
> >
> >Best regards,
> >--
> >Justin Stitt <justinstitt@google.com>
> >
>
>
> --
> Kees Cook

Thanks for the feedback. v2 available here:
https://lore.kernel.org/all/20230802-wifi-ipw2x00-refactor-v2-1-d33f765e9cd5@google.com/
diff mbox series

Patch

diff --git a/drivers/net/wireless/intel/ipw2x00/ipw2200.c b/drivers/net/wireless/intel/ipw2x00/ipw2200.c
index dfe0f74369e6..ac10633f593e 100644
--- a/drivers/net/wireless/intel/ipw2x00/ipw2200.c
+++ b/drivers/net/wireless/intel/ipw2x00/ipw2200.c
@@ -1176,23 +1176,20 @@  static ssize_t debug_level_show(struct device_driver *d, char *buf)
 static ssize_t debug_level_store(struct device_driver *d, const char *buf,
 				 size_t count)
 {
-	char *p = (char *)buf;
-	u32 val;
+	unsigned long *val = NULL;
 
-	if (p[1] == 'x' || p[1] == 'X' || p[0] == 'x' || p[0] == 'X') {
-		p++;
-		if (p[0] == 'x' || p[0] == 'X')
-			p++;
-		val = simple_strtoul(p, &p, 16);
-	} else
-		val = simple_strtoul(p, &p, 10);
-	if (p == buf)
+	int result = kstrtoul(buf, 0, val);
+
+	if (result == -EINVAL)
 		printk(KERN_INFO DRV_NAME
 		       ": %s is not in hex or decimal form.\n", buf);
+	else if (result == -ERANGE)
+		printk(KERN_INFO DRV_NAME
+			 ": %s has overflowed.\n", buf);
 	else
-		ipw_debug_level = val;
+		ipw_debug_level = *val;
 
-	return strnlen(buf, count);
+	return count;
 }
 static DRIVER_ATTR_RW(debug_level);
 
@@ -1461,33 +1458,21 @@  static ssize_t scan_age_store(struct device *d, struct device_attribute *attr,
 {
 	struct ipw_priv *priv = dev_get_drvdata(d);
 	struct net_device *dev = priv->net_dev;
-	char buffer[] = "00000000";
-	unsigned long len =
-	    (sizeof(buffer) - 1) > count ? count : sizeof(buffer) - 1;
-	unsigned long val;
-	char *p = buffer;
 
 	IPW_DEBUG_INFO("enter\n");
 
-	strncpy(buffer, buf, len);
-	buffer[len] = 0;
+	unsigned long *val = NULL;
+	int result = kstrtoul(buf, 0, val);
 
-	if (p[1] == 'x' || p[1] == 'X' || p[0] == 'x' || p[0] == 'X') {
-		p++;
-		if (p[0] == 'x' || p[0] == 'X')
-			p++;
-		val = simple_strtoul(p, &p, 16);
-	} else
-		val = simple_strtoul(p, &p, 10);
-	if (p == buffer) {
+	if (result == -EINVAL || result == -ERANGE) {
 		IPW_DEBUG_INFO("%s: user supplied invalid value.\n", dev->name);
 	} else {
-		priv->ieee->scan_age = val;
+		priv->ieee->scan_age = *val;
 		IPW_DEBUG_INFO("set scan_age = %u\n", priv->ieee->scan_age);
 	}
 
 	IPW_DEBUG_INFO("exit\n");
-	return len;
+	return count;
 }
 
 static DEVICE_ATTR_RW(scan_age);