[PATCH net-next] net: mana: hardening: Validate adapter_mtu from MANA_QUERY_DEV_CONFIG

[PATCH net-next] net: mana: hardening: Validate adapter_mtu from MANA_QUERY_DEV_CONFIG

[Erni Sri Satya Vennela]

As a part of MANA hardening for CVM, validate the adapter_mtu value
returned from the MANA_QUERY_DEV_CONFIG HWC command.

The adapter_mtu value is used to compute ndev->max_mtu via:
gc->adapter_mtu - ETH_HLEN. If hardware returns a bogus adapter_mtu
smaller than ETH_HLEN (e.g. 0), the unsigned subtraction wraps to a
huge value, silently allowing oversized MTU settings.

Add a validation check to reject adapter_mtu values below
ETH_MIN_MTU + ETH_HLEN, returning -EPROTO to fail the device
configuration early with a clear error message.

Signed-off-by: Erni Sri Satya Vennela <ernis@linux.microsoft.com>
---
 drivers/net/ethernet/microsoft/mana/mana_en.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
index b39e8b920791..bd07d17a6017 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_en.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
@@ -1207,10 +1207,16 @@ static int mana_query_device_cfg(struct mana_context *ac, u32 proto_major_ver,
 
 	*max_num_vports = resp.max_num_vports;
 
-	if (resp.hdr.response.msg_version >= GDMA_MESSAGE_V2)
+	if (resp.hdr.response.msg_version >= GDMA_MESSAGE_V2) {
+		if (resp.adapter_mtu < ETH_MIN_MTU + ETH_HLEN) {
+			dev_err(dev, "Adapter MTU too small: %u\n",
+				resp.adapter_mtu);
+			return -EPROTO;
+		}
 		gc->adapter_mtu = resp.adapter_mtu;
-	else
+	} else {
 		gc->adapter_mtu = ETH_FRAME_LEN;
+	}
 
 	if (resp.hdr.response.msg_version >= GDMA_MESSAGE_V3)
 		*bm_hostmode = resp.bm_hostmode;
-- 
2.34.1

Re: [PATCH net-next] net: mana: hardening: Validate adapter_mtu from MANA_QUERY_DEV_CONFIG

[Paolo Abeni]

On 3/26/26 6:30 PM, Erni Sri Satya Vennela wrote:
> As a part of MANA hardening for CVM, validate the adapter_mtu value
> returned from the MANA_QUERY_DEV_CONFIG HWC command.
> 
> The adapter_mtu value is used to compute ndev->max_mtu via:
> gc->adapter_mtu - ETH_HLEN. If hardware returns a bogus adapter_mtu
> smaller than ETH_HLEN (e.g. 0), the unsigned subtraction wraps to a
> huge value, silently allowing oversized MTU settings.
> 
> Add a validation check to reject adapter_mtu values below
> ETH_MIN_MTU + ETH_HLEN, returning -EPROTO to fail the device
> configuration early with a clear error message.
> 
> Signed-off-by: Erni Sri Satya Vennela <ernis@linux.microsoft.com>
> ---
>  drivers/net/ethernet/microsoft/mana/mana_en.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
> index b39e8b920791..bd07d17a6017 100644
> --- a/drivers/net/ethernet/microsoft/mana/mana_en.c
> +++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
> @@ -1207,10 +1207,16 @@ static int mana_query_device_cfg(struct mana_context *ac, u32 proto_major_ver,
>  
>  	*max_num_vports = resp.max_num_vports;
>  
> -	if (resp.hdr.response.msg_version >= GDMA_MESSAGE_V2)
> +	if (resp.hdr.response.msg_version >= GDMA_MESSAGE_V2) {
> +		if (resp.adapter_mtu < ETH_MIN_MTU + ETH_HLEN) {
> +			dev_err(dev, "Adapter MTU too small: %u\n",
> +				resp.adapter_mtu);
> +			return -EPROTO;

AI review says:

If this returns -EPROTO, does the caller mana_probe() jump to an error
label and call mana_remove()?
If so, mana_remove() unconditionally calls
disable_work_sync(&ac->link_change_work) and
cancel_delayed_work_sync(&ac->gf_stats_work).
Since mana_query_device_cfg() is called before INIT_WORK() and
INIT_DELAYED_WORK() in the probe sequence, wouldn't this result in
calling sync cancellation functions on uninitialized, zeroed work
structures?
This can lead to a WARN_ON(!work->func) in __flush_work(), or debug
object warnings if CONFIG_DEBUG_OBJECTS_WORK is enabled.
While this initialization issue appears to already exist for other early
error paths, this new error path can also trigger it.

Re: [PATCH net-next] net: mana: hardening: Validate adapter_mtu from MANA_QUERY_DEV_CONFIG

[Erni Sri Satya Vennela]

> > -	if (resp.hdr.response.msg_version >= GDMA_MESSAGE_V2)
> > +	if (resp.hdr.response.msg_version >= GDMA_MESSAGE_V2) {
> > +		if (resp.adapter_mtu < ETH_MIN_MTU + ETH_HLEN) {
> > +			dev_err(dev, "Adapter MTU too small: %u\n",
> > +				resp.adapter_mtu);
> > +			return -EPROTO;
> 
> AI review says:
> 
> If this returns -EPROTO, does the caller mana_probe() jump to an error
> label and call mana_remove()?
> If so, mana_remove() unconditionally calls
> disable_work_sync(&ac->link_change_work) and
> cancel_delayed_work_sync(&ac->gf_stats_work).
> Since mana_query_device_cfg() is called before INIT_WORK() and
> INIT_DELAYED_WORK() in the probe sequence, wouldn't this result in
> calling sync cancellation functions on uninitialized, zeroed work
> structures?
> This can lead to a WARN_ON(!work->func) in __flush_work(), or debug
> object warnings if CONFIG_DEBUG_OBJECTS_WORK is enabled.
> While this initialization issue appears to already exist for other early
> error paths, this new error path can also trigger it.

Thankyou for the review.
Since the issue is pre-existing. I will send it in a separate patchset.
The patchset will include the the issue reported with:
[PATCH net-next] net: mana: hardening: Reject zero max_num_queues from
MANA_QUERY_VPORT_CONFIG

- Vennela

Re: [PATCH net-next] net: mana: hardening: Validate adapter_mtu from MANA_QUERY_DEV_CONFIG

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Thu, 26 Mar 2026 10:30:56 -0700 you wrote:
> As a part of MANA hardening for CVM, validate the adapter_mtu value
> returned from the MANA_QUERY_DEV_CONFIG HWC command.
> 
> The adapter_mtu value is used to compute ndev->max_mtu via:
> gc->adapter_mtu - ETH_HLEN. If hardware returns a bogus adapter_mtu
> smaller than ETH_HLEN (e.g. 0), the unsigned subtraction wraps to a
> huge value, silently allowing oversized MTU settings.
> 
> [...]

Here is the summary with links:
  - [net-next] net: mana: hardening: Validate adapter_mtu from MANA_QUERY_DEV_CONFIG
    https://git.kernel.org/netdev/net-next/c/d7709812e13d

You are awesome, thank you!
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