[v2] wifi: mt76: Fix strscpy buffer overflow in mt76_connac2_load_patch

[PATCH v2] wifi: mt76: Fix strscpy buffer overflow in mt76_connac2_load_patch

Posted by Mikhail Gavrilov 1 week, 6 days ago

Commit f804a5895eba ("wifi: mt76: Strip whitespace from build ddate") introduced
a kernel panic/WARN on systems using MediaTek MT7921e (and potentially others
using mt76_connac_lib) due to an incorrect buffer size calculation.

The error logged is:
"strnlen: detected buffer overflow: 17 byte read of buffer size 16"

This occurs because the field 'hdr->build_date' is a fixed-size array of 16 bytes.
The patch allocated a 17-byte local buffer 'build_date' but used 'sizeof(build_date)'
(17) as the read limit for strscpy, causing Fortify Source to correctly detect
an attempt to read 17 bytes from the 16-byte source field.

To fix this, replace strscpy with memcpy, which is appropriate for raw data
copying, and explicitly use the size of the source field (sizeof(hdr->build_date) = 16)
to limit the read, followed by manual null termination.

Fixes: f804a5895eba ("wifi: mt76: Strip whitespace from build ddate")
Signed-off-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
---
 drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c b/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c
index ea99167765b0..d2c4c65ec464 100644
--- a/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c
+++ b/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c
@@ -3125,8 +3125,11 @@ int mt76_connac2_load_patch(struct mt76_dev *dev, const char *fw_name)
 	}
 
 	hdr = (const void *)fw->data;
-	strscpy(build_date, hdr->build_date, sizeof(build_date));
-	build_date[16] = '\0';
+	/* hdr->build_date is 16 bytes. Copy exactly 16 bytes to the 17-byte buffer,
+	 * and then add the null terminator at index 16.
+	 */
+	memcpy(build_date, hdr->build_date, sizeof(hdr->build_date));
+	build_date[sizeof(hdr->build_date)] = '\0';
 	strim(build_date);
 	dev_info(dev->dev, "HW/SW Version: 0x%x, Build Time: %.16s\n",
 		 be32_to_cpu(hdr->hw_sw_ver), build_date);
-- 
2.52.0

Re: [PATCH v2] wifi: mt76: Fix strscpy buffer overflow in mt76_connac2_load_patch

Posted by Eric Biggers 6 days, 10 hours ago

On Fri, Dec 05, 2025 at 09:12:02PM +0500, Mikhail Gavrilov wrote:
> Commit f804a5895eba ("wifi: mt76: Strip whitespace from build ddate") introduced
> a kernel panic/WARN on systems using MediaTek MT7921e (and potentially others
> using mt76_connac_lib) due to an incorrect buffer size calculation.
> 
> The error logged is:
> "strnlen: detected buffer overflow: 17 byte read of buffer size 16"
> 
> This occurs because the field 'hdr->build_date' is a fixed-size array of 16 bytes.
> The patch allocated a 17-byte local buffer 'build_date' but used 'sizeof(build_date)'
> (17) as the read limit for strscpy, causing Fortify Source to correctly detect
> an attempt to read 17 bytes from the 16-byte source field.
> 
> To fix this, replace strscpy with memcpy, which is appropriate for raw data
> copying, and explicitly use the size of the source field (sizeof(hdr->build_date) = 16)
> to limit the read, followed by manual null termination.
> 
> Fixes: f804a5895eba ("wifi: mt76: Strip whitespace from build ddate")
> Signed-off-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
> ---
>  drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c b/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c
> index ea99167765b0..d2c4c65ec464 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c
> +++ b/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c
> @@ -3125,8 +3125,11 @@ int mt76_connac2_load_patch(struct mt76_dev *dev, const char *fw_name)
>  	}
>  
>  	hdr = (const void *)fw->data;
> -	strscpy(build_date, hdr->build_date, sizeof(build_date));
> -	build_date[16] = '\0';
> +	/* hdr->build_date is 16 bytes. Copy exactly 16 bytes to the 17-byte buffer,
> +	 * and then add the null terminator at index 16.
> +	 */
> +	memcpy(build_date, hdr->build_date, sizeof(hdr->build_date));
> +	build_date[sizeof(hdr->build_date)] = '\0';
>  	strim(build_date);
>  	dev_info(dev->dev, "HW/SW Version: 0x%x, Build Time: %.16s\n",
>  		 be32_to_cpu(hdr->hw_sw_ver), build_date);

Tested-by: Eric Biggers <ebiggers@kernel.org>

Can this be sent upstream soon?

- Eric

Re: [PATCH v2] wifi: mt76: Fix strscpy buffer overflow in mt76_connac2_load_patch

Posted by Mario Limonciello (AMD) (kernel.org) 6 days, 10 hours ago


On 12/12/2025 8:35 PM, Eric Biggers wrote:
> On Fri, Dec 05, 2025 at 09:12:02PM +0500, Mikhail Gavrilov wrote:
>> Commit f804a5895eba ("wifi: mt76: Strip whitespace from build ddate") introduced
>> a kernel panic/WARN on systems using MediaTek MT7921e (and potentially others
>> using mt76_connac_lib) due to an incorrect buffer size calculation.
>>
>> The error logged is:
>> "strnlen: detected buffer overflow: 17 byte read of buffer size 16"
>>
>> This occurs because the field 'hdr->build_date' is a fixed-size array of 16 bytes.
>> The patch allocated a 17-byte local buffer 'build_date' but used 'sizeof(build_date)'
>> (17) as the read limit for strscpy, causing Fortify Source to correctly detect
>> an attempt to read 17 bytes from the 16-byte source field.
>>
>> To fix this, replace strscpy with memcpy, which is appropriate for raw data
>> copying, and explicitly use the size of the source field (sizeof(hdr->build_date) = 16)
>> to limit the read, followed by manual null termination.
>>
>> Fixes: f804a5895eba ("wifi: mt76: Strip whitespace from build ddate")
>> Signed-off-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
>> ---
>>   drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c | 7 +++++--
>>   1 file changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c b/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c
>> index ea99167765b0..d2c4c65ec464 100644
>> --- a/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c
>> +++ b/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c
>> @@ -3125,8 +3125,11 @@ int mt76_connac2_load_patch(struct mt76_dev *dev, const char *fw_name)
>>   	}
>>   
>>   	hdr = (const void *)fw->data;
>> -	strscpy(build_date, hdr->build_date, sizeof(build_date));
>> -	build_date[16] = '\0';
>> +	/* hdr->build_date is 16 bytes. Copy exactly 16 bytes to the 17-byte buffer,
>> +	 * and then add the null terminator at index 16.
>> +	 */
>> +	memcpy(build_date, hdr->build_date, sizeof(hdr->build_date));
>> +	build_date[sizeof(hdr->build_date)] = '\0';
>>   	strim(build_date);
>>   	dev_info(dev->dev, "HW/SW Version: 0x%x, Build Time: %.16s\n",
>>   		 be32_to_cpu(hdr->hw_sw_ver), build_date);
> 
> Tested-by: Eric Biggers <ebiggers@kernel.org>
> 
> Can this be sent upstream soon?
> 
> - Eric

Tested-by: Mario Limonciello (AMD) <superm1@kernel.org>

Re: [PATCH v2] wifi: mt76: Fix strscpy buffer overflow in mt76_connac2_load_patch

Posted by Mario Limonciello 1 week, 6 days ago

On 12/5/25 10:12 AM, Mikhail Gavrilov wrote:
> Commit f804a5895eba ("wifi: mt76: Strip whitespace from build ddate") introduced
> a kernel panic/WARN on systems using MediaTek MT7921e (and potentially others
> using mt76_connac_lib) due to an incorrect buffer size calculation.
> 
> The error logged is:
> "strnlen: detected buffer overflow: 17 byte read of buffer size 16"
> 
> This occurs because the field 'hdr->build_date' is a fixed-size array of 16 bytes.
> The patch allocated a 17-byte local buffer 'build_date' but used 'sizeof(build_date)'
> (17) as the read limit for strscpy, causing Fortify Source to correctly detect
> an attempt to read 17 bytes from the 16-byte source field.
> 
> To fix this, replace strscpy with memcpy, which is appropriate for raw data
> copying, and explicitly use the size of the source field (sizeof(hdr->build_date) = 16)
> to limit the read, followed by manual null termination.
> 
> Fixes: f804a5895eba ("wifi: mt76: Strip whitespace from build ddate")
> Signed-off-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>

Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>

> ---
>   drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c | 7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c b/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c
> index ea99167765b0..d2c4c65ec464 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c
> +++ b/drivers/net/wireless/mediatek/mt76/mt76_connac_mcu.c
> @@ -3125,8 +3125,11 @@ int mt76_connac2_load_patch(struct mt76_dev *dev, const char *fw_name)
>   	}
>   
>   	hdr = (const void *)fw->data;
> -	strscpy(build_date, hdr->build_date, sizeof(build_date));
> -	build_date[16] = '\0';
> +	/* hdr->build_date is 16 bytes. Copy exactly 16 bytes to the 17-byte buffer,
> +	 * and then add the null terminator at index 16.
> +	 */
> +	memcpy(build_date, hdr->build_date, sizeof(hdr->build_date));
> +	build_date[sizeof(hdr->build_date)] = '\0';
>   	strim(build_date);
>   	dev_info(dev->dev, "HW/SW Version: 0x%x, Build Time: %.16s\n",
>   		 be32_to_cpu(hdr->hw_sw_ver), build_date);