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[PATCH] net: core: prevent NULL deref in generic_hwtstamp_ioctl_lower()

Jiaming Zhang posted 1 patch 3 months, 1 week ago
There is a newer version of this series
net/core/dev_ioctl.c | 8 ++++++++
1 file changed, 8 insertions(+)
[PATCH] net: core: prevent NULL deref in generic_hwtstamp_ioctl_lower()
Posted by Jiaming Zhang 3 months, 1 week ago 
The ethtool tsconfig Netlink path can trigger a null pointer
dereference. A call chain such as:

  tsconfig_prepare_data() ->
  dev_get_hwtstamp_phylib() ->
  vlan_hwtstamp_get() ->
  generic_hwtstamp_get_lower() ->
  generic_hwtstamp_ioctl_lower()

results in generic_hwtstamp_ioctl_lower() being called with
kernel_cfg->ifr as NULL.

The generic_hwtstamp_ioctl_lower() function does not expect a
NULL ifr and dereferences it, leading to a system crash.

Fix this by adding a NULL check for kernel_cfg->ifr in
generic_hwtstamp_get/set_lower(). If ifr is NULL, return
-EOPNOTSUPP to prevent the call to the legacy IOCTL helper.

Fixes: 6e9e2eed4f39 ("net: ethtool: Add support for tsconfig command to get/set hwtstamp config")
Closes: https://lore.kernel.org/lkml/cd6a7056-fa6d-43f8-b78a-f5e811247ba8@linux.dev/T/#mf5df538e21753e3045de98f25aa18d948be07df3
Signed-off-by: Jiaming Zhang <r772577952@gmail.com>
---
 net/core/dev_ioctl.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/core/dev_ioctl.c b/net/core/dev_ioctl.c
index ad54b12d4b4c..39eaf6ba981a 100644
--- a/net/core/dev_ioctl.c
+++ b/net/core/dev_ioctl.c
@@ -474,6 +474,10 @@ int generic_hwtstamp_get_lower(struct net_device *dev,
 		return err;
 	}
 
+	/* Netlink path with unconverted driver */
+	if (!kernel_cfg->ifr)
+		return -EOPNOTSUPP;
+
 	/* Legacy path: unconverted lower driver */
 	return generic_hwtstamp_ioctl_lower(dev, SIOCGHWTSTAMP, kernel_cfg);
 }
@@ -498,6 +502,10 @@ int generic_hwtstamp_set_lower(struct net_device *dev,
 		return err;
 	}
 
+	/* Netlink path with unconverted driver */
+	if (!kernel_cfg->ifr)
+		return -EOPNOTSUPP;
+
 	/* Legacy path: unconverted lower driver */
 	return generic_hwtstamp_ioctl_lower(dev, SIOCSHWTSTAMP, kernel_cfg);
 }
-- 
2.34.1
Re: [PATCH] net: core: prevent NULL deref in generic_hwtstamp_ioctl_lower()
Posted by Kory Maincent 3 months, 1 week ago 
On Thu, 30 Oct 2025 09:36:21 +0000
Jiaming Zhang <r772577952@gmail.com> wrote:

> The ethtool tsconfig Netlink path can trigger a null pointer
> dereference. A call chain such as:
> 
>   tsconfig_prepare_data() ->
>   dev_get_hwtstamp_phylib() ->
>   vlan_hwtstamp_get() ->
>   generic_hwtstamp_get_lower() ->
>   generic_hwtstamp_ioctl_lower()
> 
> results in generic_hwtstamp_ioctl_lower() being called with
> kernel_cfg->ifr as NULL.
> 
> The generic_hwtstamp_ioctl_lower() function does not expect a
> NULL ifr and dereferences it, leading to a system crash.
> 
> Fix this by adding a NULL check for kernel_cfg->ifr in
> generic_hwtstamp_get/set_lower(). If ifr is NULL, return
> -EOPNOTSUPP to prevent the call to the legacy IOCTL helper.
> 
> Fixes: 6e9e2eed4f39 ("net: ethtool: Add support for tsconfig command to
> get/set hwtstamp config") Closes:
> https://lore.kernel.org/lkml/cd6a7056-fa6d-43f8-b78a-f5e811247ba8@linux.dev/T/#mf5df538e21753e3045de98f25aa18d948be07df3
> Signed-off-by: Jiaming Zhang <r772577952@gmail.com> ---
>  net/core/dev_ioctl.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/net/core/dev_ioctl.c b/net/core/dev_ioctl.c
> index ad54b12d4b4c..39eaf6ba981a 100644
> --- a/net/core/dev_ioctl.c
> +++ b/net/core/dev_ioctl.c
> @@ -474,6 +474,10 @@ int generic_hwtstamp_get_lower(struct net_device *dev,
>  		return err;
>  	}
>  
> +	/* Netlink path with unconverted driver */

nit: "lower driver", to be precise.

With this change:
Reviewed-by: Kory Maincent <kory.maincent@bootlin.com>

Thank you!

> +	if (!kernel_cfg->ifr)
> +		return -EOPNOTSUPP;
> +
>  	/* Legacy path: unconverted lower driver */
>  	return generic_hwtstamp_ioctl_lower(dev, SIOCGHWTSTAMP, kernel_cfg);
>  }
> @@ -498,6 +502,10 @@ int generic_hwtstamp_set_lower(struct net_device *dev,
>  		return err;
>  	}
>  
> +	/* Netlink path with unconverted driver */

same.

> +	if (!kernel_cfg->ifr)
> +		return -EOPNOTSUPP;
> +
>  	/* Legacy path: unconverted lower driver */
>  	return generic_hwtstamp_ioctl_lower(dev, SIOCSHWTSTAMP, kernel_cfg);
>  }



-- 
Köry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com
[PATCH v3 0/1] net: core: prevent NULL deref in generic_hwtstamp_ioctl_lower()
Posted by Jiaming Zhang 3 months, 1 week ago 
Hi Kory,

Apologies for the resubmission (v3); I forgot to add Reviewed-by tag in
the v2 patch.

v3:
- Add Kory's Reviewed-by tag.

v2:
- Fix typo in comment ("driver" -> "lower driver")

Best Regards,
Jiaming Zhang

Jiaming Zhang (1):
  net: core: prevent NULL deref in generic_hwtstamp_ioctl_lower()

 net/core/dev_ioctl.c | 8 ++++++++
 1 file changed, 8 insertions(+)

-- 
2.34.1
[PATCH v3 1/1] net: core: prevent NULL deref in generic_hwtstamp_ioctl_lower()
Posted by Jiaming Zhang 3 months, 1 week ago 
The ethtool tsconfig Netlink path can trigger a null pointer
dereference. A call chain such as:

  tsconfig_prepare_data() ->
  dev_get_hwtstamp_phylib() ->
  vlan_hwtstamp_get() ->
  generic_hwtstamp_get_lower() ->
  generic_hwtstamp_ioctl_lower()

results in generic_hwtstamp_ioctl_lower() being called with
kernel_cfg->ifr as NULL.

The generic_hwtstamp_ioctl_lower() function does not expect a
NULL ifr and dereferences it, leading to a system crash.

Fix this by adding a NULL check for kernel_cfg->ifr in
generic_hwtstamp_get/set_lower(). If ifr is NULL, return
-EOPNOTSUPP to prevent the call to the legacy IOCTL helper.

Fixes: 6e9e2eed4f39 ("net: ethtool: Add support for tsconfig command to get/set hwtstamp config")
Closes: https://lore.kernel.org/lkml/cd6a7056-fa6d-43f8-b78a-f5e811247ba8@linux.dev/T/#mf5df538e21753e3045de98f25aa18d948be07df3
Signed-off-by: Jiaming Zhang <r772577952@gmail.com>
Reviewed-by: Kory Maincent <kory.maincent@bootlin.com>
---
 net/core/dev_ioctl.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/core/dev_ioctl.c b/net/core/dev_ioctl.c
index ad54b12d4b4c..a32e1036f12a 100644
--- a/net/core/dev_ioctl.c
+++ b/net/core/dev_ioctl.c
@@ -474,6 +474,10 @@ int generic_hwtstamp_get_lower(struct net_device *dev,
 		return err;
 	}
 
+	/* Netlink path with unconverted lower driver */
+	if (!kernel_cfg->ifr)
+		return -EOPNOTSUPP;
+
 	/* Legacy path: unconverted lower driver */
 	return generic_hwtstamp_ioctl_lower(dev, SIOCGHWTSTAMP, kernel_cfg);
 }
@@ -498,6 +502,10 @@ int generic_hwtstamp_set_lower(struct net_device *dev,
 		return err;
 	}
 
+	/* Netlink path with unconverted lower driver */
+	if (!kernel_cfg->ifr)
+		return -EOPNOTSUPP;
+
 	/* Legacy path: unconverted lower driver */
 	return generic_hwtstamp_ioctl_lower(dev, SIOCSHWTSTAMP, kernel_cfg);
 }
-- 
2.34.1
Re: [PATCH v3 1/1] net: core: prevent NULL deref in generic_hwtstamp_ioctl_lower()
Posted by Jakub Kicinski 3 months ago 
On Thu, 30 Oct 2025 12:49:47 +0000 Jiaming Zhang wrote:
> +	/* Netlink path with unconverted lower driver */
> +	if (!kernel_cfg->ifr)
> +		return -EOPNOTSUPP;
> +
>  	/* Legacy path: unconverted lower driver */
>  	return generic_hwtstamp_ioctl_lower(dev, SIOCGHWTSTAMP, kernel_cfg);
>  }
> @@ -498,6 +502,10 @@ int generic_hwtstamp_set_lower(struct net_device *dev,
>  		return err;
>  	}
>  
> +	/* Netlink path with unconverted lower driver */
> +	if (!kernel_cfg->ifr)
> +		return -EOPNOTSUPP;
> +
>  	/* Legacy path: unconverted lower driver */
>  	return generic_hwtstamp_ioctl_lower(dev, SIOCSHWTSTAMP, kernel_cfg);

Sorry but nit:

instead of adding this to both callers you can add the check in
generic_hwtstamp_ioctl_lower().
-- 
pw-bot: cr
[PATCH v4 0/1] net: core: prevent NULL deref in generic_hwtstamp_ioctl_lower()
Posted by Jiaming Zhang 2 months, 3 weeks ago 
Hi Jakub,

Sorry for the late response. I have updated the patch, NULL check
is moved from get/set caller to generic_hwstamp_ioctl_lower().

Please let me know if any change is needed :)

v4:
- Move NULL check from generic_hwtstamp_get/set_lower()
  to generic_hwtstamp_ioctl_lower()

v3:
- Add Kory's Reviewed-by tag.

v2:
- Fix typo in comment ("driver" -> "lower driver")

Best Regards,
Jiaming Zhang

Jiaming Zhang (1):
  net: core: prevent NULL deref in generic_hwtstamp_ioctl_lower()

 net/core/dev_ioctl.c | 3 +++
 1 file changed, 3 insertions(+)

-- 
2.34.1
[PATCH v4 1/1] net: core: prevent NULL deref in generic_hwtstamp_ioctl_lower()
Posted by Jiaming Zhang 2 months, 3 weeks ago 
The ethtool tsconfig Netlink path can trigger a null pointer
dereference. A call chain such as:

  tsconfig_prepare_data() ->
  dev_get_hwtstamp_phylib() ->
  vlan_hwtstamp_get() ->
  generic_hwtstamp_get_lower() ->
  generic_hwtstamp_ioctl_lower()

results in generic_hwtstamp_ioctl_lower() being called with
kernel_cfg->ifr as NULL.

The generic_hwtstamp_ioctl_lower() function does not expect a
NULL ifr and dereferences it, leading to a system crash.

Fix this by adding a NULL check for kernel_cfg->ifr in
generic_hwtstamp_ioctl_lower(). If ifr is NULL, return -EINVAL.

Fixes: 6e9e2eed4f39 ("net: ethtool: Add support for tsconfig command to get/set hwtstamp config")
Closes: https://lore.kernel.org/lkml/cd6a7056-fa6d-43f8-b78a-f5e811247ba8@linux.dev/T/#mf5df538e21753e3045de98f25aa18d948be07df3

Signed-off-by: Jiaming Zhang <r772577952@gmail.com>
---
 net/core/dev_ioctl.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/core/dev_ioctl.c b/net/core/dev_ioctl.c
index ad54b12d4b4c..8bb71a10dba0 100644
--- a/net/core/dev_ioctl.c
+++ b/net/core/dev_ioctl.c
@@ -443,6 +443,9 @@ static int generic_hwtstamp_ioctl_lower(struct net_device *dev, int cmd,
 	struct ifreq ifrr;
 	int err;
 
+	if (!kernel_cfg->ifr)
+		return -EINVAL;
+
 	strscpy_pad(ifrr.ifr_name, dev->name, IFNAMSIZ);
 	ifrr.ifr_ifru = kernel_cfg->ifr->ifr_ifru;
 
-- 
2.34.1
Re: [PATCH v4 1/1] net: core: prevent NULL deref in generic_hwtstamp_ioctl_lower()
Posted by Kory Maincent 2 months, 3 weeks ago 
On Wed, 12 Nov 2025 01:36:52 +0800
Jiaming Zhang <r772577952@gmail.com> wrote:

> The ethtool tsconfig Netlink path can trigger a null pointer
> dereference. A call chain such as:
> 
>   tsconfig_prepare_data() ->
>   dev_get_hwtstamp_phylib() ->
>   vlan_hwtstamp_get() ->
>   generic_hwtstamp_get_lower() ->
>   generic_hwtstamp_ioctl_lower()
> 
> results in generic_hwtstamp_ioctl_lower() being called with
> kernel_cfg->ifr as NULL.
> 
> The generic_hwtstamp_ioctl_lower() function does not expect a
> NULL ifr and dereferences it, leading to a system crash.
> 
> Fix this by adding a NULL check for kernel_cfg->ifr in
> generic_hwtstamp_ioctl_lower(). If ifr is NULL, return -EINVAL.
> 
> Fixes: 6e9e2eed4f39 ("net: ethtool: Add support for tsconfig command to
> get/set hwtstamp config") Closes:
> https://lore.kernel.org/lkml/cd6a7056-fa6d-43f8-b78a-f5e811247ba8@linux.dev/T/#mf5df538e21753e3045de98f25aa18d948be07df3
> 
> Signed-off-by: Jiaming Zhang <r772577952@gmail.com>

Reviewed-by: Kory Maincent <kory.maincent@bootlin.com>

Thank you!
-- 
Köry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com
[PATCH v2] net: core: prevent NULL deref in generic_hwtstamp_ioctl_lower()
Posted by Jiaming Zhang 3 months, 1 week ago 
The ethtool tsconfig Netlink path can trigger a null pointer
dereference. A call chain such as:

  tsconfig_prepare_data() ->
  dev_get_hwtstamp_phylib() ->
  vlan_hwtstamp_get() ->
  generic_hwtstamp_get_lower() ->
  generic_hwtstamp_ioctl_lower()

results in generic_hwtstamp_ioctl_lower() being called with
kernel_cfg->ifr as NULL.

The generic_hwtstamp_ioctl_lower() function does not expect a
NULL ifr and dereferences it, leading to a system crash.

Fix this by adding a NULL check for kernel_cfg->ifr in
generic_hwtstamp_get/set_lower(). If ifr is NULL, return
-EOPNOTSUPP to prevent the call to the legacy IOCTL helper.

Fixes: 6e9e2eed4f39 ("net: ethtool: Add support for tsconfig command to get/set hwtstamp config")
Closes: https://lore.kernel.org/lkml/cd6a7056-fa6d-43f8-b78a-f5e811247ba8@linux.dev/T/#mf5df538e21753e3045de98f25aa18d948be07df3
Signed-off-by: Jiaming Zhang <r772577952@gmail.com>
---
 net/core/dev_ioctl.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/core/dev_ioctl.c b/net/core/dev_ioctl.c
index ad54b12d4b4c..a32e1036f12a 100644
--- a/net/core/dev_ioctl.c
+++ b/net/core/dev_ioctl.c
@@ -474,6 +474,10 @@ int generic_hwtstamp_get_lower(struct net_device *dev,
 		return err;
 	}
 
+	/* Netlink path with unconverted lower driver */
+	if (!kernel_cfg->ifr)
+		return -EOPNOTSUPP;
+
 	/* Legacy path: unconverted lower driver */
 	return generic_hwtstamp_ioctl_lower(dev, SIOCGHWTSTAMP, kernel_cfg);
 }
@@ -498,6 +502,10 @@ int generic_hwtstamp_set_lower(struct net_device *dev,
 		return err;
 	}
 
+	/* Netlink path with unconverted lower driver */
+	if (!kernel_cfg->ifr)
+		return -EOPNOTSUPP;
+
 	/* Legacy path: unconverted lower driver */
 	return generic_hwtstamp_ioctl_lower(dev, SIOCSHWTSTAMP, kernel_cfg);
 }
-- 
2.34.1

Patchew 2.1-devel-b67e4c2

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