wifi: mwifiex: Fix memcpy() field-spanning write warning in mwifiex_config_scan()

[PATCH] wifi: mwifiex: Fix memcpy() field-spanning write warning in mwifiex_config_scan()

Posted by Alper Nebi Yasak 2 months, 1 week ago

Replace one-element array with a flexible-array member in `struct
mwifiex_ie_types_wildcard_ssid_params` to fix the following warning
on a MT8173 Chromebook (mt8173-elm-hana):

[  356.775250] ------------[ cut here ]------------
[  356.784543] memcpy: detected field-spanning write (size 6) of single field "wildcard_ssid_tlv->ssid" at drivers/net/wireless/marvell/mwifiex/scan.c:904 (size 1)
[  356.813403] WARNING: CPU: 3 PID: 742 at drivers/net/wireless/marvell/mwifiex/scan.c:904 mwifiex_scan_networks+0x4fc/0xf28 [mwifiex]

The "(size 6)" above is exactly the length of the SSID of the network
this device was connected to. The source of the warning looks like:

    ssid_len = user_scan_in->ssid_list[i].ssid_len;
    [...]
    memcpy(wildcard_ssid_tlv->ssid,
           user_scan_in->ssid_list[i].ssid, ssid_len);

Also adjust a #define that uses sizeof() on this struct to keep the
value same as before.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
---
I found these relevant patches that modify other such arrays, where the
second one removes a -1 from some sizeof() calculation:

https://lore.kernel.org/lkml/Y9xkECG3uTZ6T1dN@work/T/#u
https://lore.kernel.org/lkml/ZsZa5xRcsLq9D+RX@elsanto/T/#u

So I think we need the +1 to keep things same. But it appears to work
fine without it, so I'm not sure. Maybe it should've had a -1 before
that I would remove with this?

 drivers/net/wireless/marvell/mwifiex/fw.h   | 2 +-
 drivers/net/wireless/marvell/mwifiex/scan.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/marvell/mwifiex/fw.h b/drivers/net/wireless/marvell/mwifiex/fw.h
index d03129d5d24e..4a96281792cc 100644
--- a/drivers/net/wireless/marvell/mwifiex/fw.h
+++ b/drivers/net/wireless/marvell/mwifiex/fw.h
@@ -875,7 +875,7 @@ struct mwifiex_ietypes_chanstats {
 struct mwifiex_ie_types_wildcard_ssid_params {
 	struct mwifiex_ie_types_header header;
 	u8 max_ssid_length;
-	u8 ssid[1];
+	u8 ssid[];
 } __packed;
 
 #define TSF_DATA_SIZE            8
diff --git a/drivers/net/wireless/marvell/mwifiex/scan.c b/drivers/net/wireless/marvell/mwifiex/scan.c
index cab889af4c4a..50af78ee935b 100644
--- a/drivers/net/wireless/marvell/mwifiex/scan.c
+++ b/drivers/net/wireless/marvell/mwifiex/scan.c
@@ -32,7 +32,7 @@
 #define WILDCARD_SSID_TLV_MAX_SIZE  \
 	(MWIFIEX_MAX_SSID_LIST_LENGTH *					\
 		(sizeof(struct mwifiex_ie_types_wildcard_ssid_params)	\
-			+ IEEE80211_MAX_SSID_LEN))
+			+ IEEE80211_MAX_SSID_LEN + 1))
 
 /* Maximum memory needed for a mwifiex_scan_cmd_config with all TLVs at max */
 #define MAX_SCAN_CFG_ALLOC (sizeof(struct mwifiex_scan_cmd_config)        \

base-commit: 4f3e012d4cfd1d9bf837870c961f462ca9f23ebe
-- 
2.45.2

Re: [PATCH] wifi: mwifiex: Fix memcpy() field-spanning write warning in mwifiex_config_scan()

Posted by Brian Norris 1 month, 3 weeks ago

On Tue, Sep 17, 2024 at 06:08:41PM +0300, Alper Nebi Yasak wrote:
> Replace one-element array with a flexible-array member in `struct
> mwifiex_ie_types_wildcard_ssid_params` to fix the following warning
> on a MT8173 Chromebook (mt8173-elm-hana):
> 
> [  356.775250] ------------[ cut here ]------------
> [  356.784543] memcpy: detected field-spanning write (size 6) of single field "wildcard_ssid_tlv->ssid" at drivers/net/wireless/marvell/mwifiex/scan.c:904 (size 1)
> [  356.813403] WARNING: CPU: 3 PID: 742 at drivers/net/wireless/marvell/mwifiex/scan.c:904 mwifiex_scan_networks+0x4fc/0xf28 [mwifiex]
> 
> The "(size 6)" above is exactly the length of the SSID of the network
> this device was connected to. The source of the warning looks like:
> 
>     ssid_len = user_scan_in->ssid_list[i].ssid_len;
>     [...]
>     memcpy(wildcard_ssid_tlv->ssid,
>            user_scan_in->ssid_list[i].ssid, ssid_len);
> 
> Also adjust a #define that uses sizeof() on this struct to keep the
> value same as before.
> 
> Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
> ---
> I found these relevant patches that modify other such arrays, where the
> second one removes a -1 from some sizeof() calculation:
> 
> https://lore.kernel.org/lkml/Y9xkECG3uTZ6T1dN@work/T/#u
> https://lore.kernel.org/lkml/ZsZa5xRcsLq9D+RX@elsanto/T/#u
> 
> So I think we need the +1 to keep things same. But it appears to work
> fine without it, so I'm not sure. Maybe it should've had a -1 before
> that I would remove with this?

Thanks for the investigation and patch! I believe I agree with the other
comments, that then "+ 1" isn't necessary. It's just a wasteful extra
byte of allocation. Can you send a v2? (Bonus: with the suggested Fixes
tag. Double bonus if you test KASAN with __counted_by, for a second
patch.)

Thanks,
Brian

Re: [PATCH] wifi: mwifiex: Fix memcpy() field-spanning write warning in mwifiex_config_scan()

Posted by Jeff Johnson 2 months, 1 week ago

On 9/17/2024 8:08 AM, Alper Nebi Yasak wrote:
> Replace one-element array with a flexible-array member in `struct
> mwifiex_ie_types_wildcard_ssid_params` to fix the following warning
> on a MT8173 Chromebook (mt8173-elm-hana):
> 
> [  356.775250] ------------[ cut here ]------------
> [  356.784543] memcpy: detected field-spanning write (size 6) of single field "wildcard_ssid_tlv->ssid" at drivers/net/wireless/marvell/mwifiex/scan.c:904 (size 1)
> [  356.813403] WARNING: CPU: 3 PID: 742 at drivers/net/wireless/marvell/mwifiex/scan.c:904 mwifiex_scan_networks+0x4fc/0xf28 [mwifiex]
> 
> The "(size 6)" above is exactly the length of the SSID of the network
> this device was connected to. The source of the warning looks like:
> 
>     ssid_len = user_scan_in->ssid_list[i].ssid_len;
>     [...]
>     memcpy(wildcard_ssid_tlv->ssid,
>            user_scan_in->ssid_list[i].ssid, ssid_len);
> 
> Also adjust a #define that uses sizeof() on this struct to keep the
> value same as before.
> 
> Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
> ---
> I found these relevant patches that modify other such arrays, where the
> second one removes a -1 from some sizeof() calculation:
> 
> https://lore.kernel.org/lkml/Y9xkECG3uTZ6T1dN@work/T/#u
> https://lore.kernel.org/lkml/ZsZa5xRcsLq9D+RX@elsanto/T/#u
> 
> So I think we need the +1 to keep things same. But it appears to work
> fine without it, so I'm not sure. Maybe it should've had a -1 before
> that I would remove with this?

I think the original code was incorrect and was allocating too much memory.
I do not think WILDCARD_SSID_TLV_MAX_SIZE requires modification.

> 
>  drivers/net/wireless/marvell/mwifiex/fw.h   | 2 +-
>  drivers/net/wireless/marvell/mwifiex/scan.c | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/wireless/marvell/mwifiex/fw.h b/drivers/net/wireless/marvell/mwifiex/fw.h
> index d03129d5d24e..4a96281792cc 100644
> --- a/drivers/net/wireless/marvell/mwifiex/fw.h
> +++ b/drivers/net/wireless/marvell/mwifiex/fw.h
> @@ -875,7 +875,7 @@ struct mwifiex_ietypes_chanstats {
>  struct mwifiex_ie_types_wildcard_ssid_params {
>  	struct mwifiex_ie_types_header header;
>  	u8 max_ssid_length;
> -	u8 ssid[1];
> +	u8 ssid[];
>  } __packed;
>  
>  #define TSF_DATA_SIZE            8
> diff --git a/drivers/net/wireless/marvell/mwifiex/scan.c b/drivers/net/wireless/marvell/mwifiex/scan.c
> index cab889af4c4a..50af78ee935b 100644
> --- a/drivers/net/wireless/marvell/mwifiex/scan.c
> +++ b/drivers/net/wireless/marvell/mwifiex/scan.c
> @@ -32,7 +32,7 @@
>  #define WILDCARD_SSID_TLV_MAX_SIZE  \
>  	(MWIFIEX_MAX_SSID_LIST_LENGTH *					\
>  		(sizeof(struct mwifiex_ie_types_wildcard_ssid_params)	\
> -			+ IEEE80211_MAX_SSID_LEN))
> +			+ IEEE80211_MAX_SSID_LEN + 1))
>  
>  /* Maximum memory needed for a mwifiex_scan_cmd_config with all TLVs at max */
>  #define MAX_SCAN_CFG_ALLOC (sizeof(struct mwifiex_scan_cmd_config)        \
> 
> base-commit: 4f3e012d4cfd1d9bf837870c961f462ca9f23ebe

Re: [PATCH] wifi: mwifiex: Fix memcpy() field-spanning write warning in mwifiex_config_scan()

Posted by Gustavo A. R. Silva 2 months, 1 week ago


On 17/09/24 20:10, Jeff Johnson wrote:
> On 9/17/2024 8:08 AM, Alper Nebi Yasak wrote:
>> Replace one-element array with a flexible-array member in `struct
>> mwifiex_ie_types_wildcard_ssid_params` to fix the following warning
>> on a MT8173 Chromebook (mt8173-elm-hana):
>>
>> [  356.775250] ------------[ cut here ]------------
>> [  356.784543] memcpy: detected field-spanning write (size 6) of single field "wildcard_ssid_tlv->ssid" at drivers/net/wireless/marvell/mwifiex/scan.c:904 (size 1)
>> [  356.813403] WARNING: CPU: 3 PID: 742 at drivers/net/wireless/marvell/mwifiex/scan.c:904 mwifiex_scan_networks+0x4fc/0xf28 [mwifiex]
>>
>> The "(size 6)" above is exactly the length of the SSID of the network
>> this device was connected to. The source of the warning looks like:
>>
>>      ssid_len = user_scan_in->ssid_list[i].ssid_len;
>>      [...]
>>      memcpy(wildcard_ssid_tlv->ssid,
>>             user_scan_in->ssid_list[i].ssid, ssid_len);
>>
>> Also adjust a #define that uses sizeof() on this struct to keep the
>> value same as before.
>>
>> Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
>> ---
>> I found these relevant patches that modify other such arrays, where the
>> second one removes a -1 from some sizeof() calculation:
>>
>> https://lore.kernel.org/lkml/Y9xkECG3uTZ6T1dN@work/T/#u
>> https://lore.kernel.org/lkml/ZsZa5xRcsLq9D+RX@elsanto/T/#u
>>
>> So I think we need the +1 to keep things same. But it appears to work
>> fine without it, so I'm not sure. Maybe it should've had a -1 before
>> that I would remove with this?
> 
> I think the original code was incorrect and was allocating too much memory.
> I do not think WILDCARD_SSID_TLV_MAX_SIZE requires modification.

If this is case, I think the changelog text should include the following
'Fixes' tag (and the `__counted_by` annotation added in a separate patch):

Fixes: 5e6e3a92b9a4 ("wireless: mwifiex: initial commit for Marvell mwifiex driver")

Thanks
--
Gustavo

> 
>>
>>   drivers/net/wireless/marvell/mwifiex/fw.h   | 2 +-
>>   drivers/net/wireless/marvell/mwifiex/scan.c | 2 +-
>>   2 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/net/wireless/marvell/mwifiex/fw.h b/drivers/net/wireless/marvell/mwifiex/fw.h
>> index d03129d5d24e..4a96281792cc 100644
>> --- a/drivers/net/wireless/marvell/mwifiex/fw.h
>> +++ b/drivers/net/wireless/marvell/mwifiex/fw.h
>> @@ -875,7 +875,7 @@ struct mwifiex_ietypes_chanstats {
>>   struct mwifiex_ie_types_wildcard_ssid_params {
>>   	struct mwifiex_ie_types_header header;
>>   	u8 max_ssid_length;
>> -	u8 ssid[1];
>> +	u8 ssid[];
>>   } __packed;
>>   
>>   #define TSF_DATA_SIZE            8
>> diff --git a/drivers/net/wireless/marvell/mwifiex/scan.c b/drivers/net/wireless/marvell/mwifiex/scan.c
>> index cab889af4c4a..50af78ee935b 100644
>> --- a/drivers/net/wireless/marvell/mwifiex/scan.c
>> +++ b/drivers/net/wireless/marvell/mwifiex/scan.c
>> @@ -32,7 +32,7 @@
>>   #define WILDCARD_SSID_TLV_MAX_SIZE  \
>>   	(MWIFIEX_MAX_SSID_LIST_LENGTH *					\
>>   		(sizeof(struct mwifiex_ie_types_wildcard_ssid_params)	\
>> -			+ IEEE80211_MAX_SSID_LEN))
>> +			+ IEEE80211_MAX_SSID_LEN + 1))
>>   
>>   /* Maximum memory needed for a mwifiex_scan_cmd_config with all TLVs at max */
>>   #define MAX_SCAN_CFG_ALLOC (sizeof(struct mwifiex_scan_cmd_config)        \
>>
>> base-commit: 4f3e012d4cfd1d9bf837870c961f462ca9f23ebe
>

Re: [PATCH] wifi: mwifiex: Fix memcpy() field-spanning write warning in mwifiex_config_scan()

Posted by Andy Shevchenko 2 months, 1 week ago

On Tue, Sep 17, 2024 at 06:08:41PM +0300, Alper Nebi Yasak wrote:
> Replace one-element array with a flexible-array member in `struct
> mwifiex_ie_types_wildcard_ssid_params` to fix the following warning
> on a MT8173 Chromebook (mt8173-elm-hana):
> 
> [  356.775250] ------------[ cut here ]------------
> [  356.784543] memcpy: detected field-spanning write (size 6) of single field "wildcard_ssid_tlv->ssid" at drivers/net/wireless/marvell/mwifiex/scan.c:904 (size 1)
> [  356.813403] WARNING: CPU: 3 PID: 742 at drivers/net/wireless/marvell/mwifiex/scan.c:904 mwifiex_scan_networks+0x4fc/0xf28 [mwifiex]
> 
> The "(size 6)" above is exactly the length of the SSID of the network
> this device was connected to. The source of the warning looks like:
> 
>     ssid_len = user_scan_in->ssid_list[i].ssid_len;
>     [...]
>     memcpy(wildcard_ssid_tlv->ssid,
>            user_scan_in->ssid_list[i].ssid, ssid_len);
> 
> Also adjust a #define that uses sizeof() on this struct to keep the
> value same as before.

...

>  #define WILDCARD_SSID_TLV_MAX_SIZE  \
>  	(MWIFIEX_MAX_SSID_LIST_LENGTH *					\
>  		(sizeof(struct mwifiex_ie_types_wildcard_ssid_params)	\
> -			+ IEEE80211_MAX_SSID_LEN))
> +			+ IEEE80211_MAX_SSID_LEN + 1))
>  

This hunk has to be carefully checked by wireless people. I'm not sure
that we need  + 1 here.

Otherwise, LGTM.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH] wifi: mwifiex: Fix memcpy() field-spanning write warning in mwifiex_config_scan()

Posted by Dmitry Antipov 2 months, 1 week ago

On 9/17/24 7:30 PM, Andy Shevchenko wrote:

> This hunk has to be carefully checked by wireless people. I'm not sure
> that we need  + 1 here.

Well, +1 looks redundant here indeed.

And if you touch this anyway, please also consider '__counted_by(max_ssid_length)'
for 'ssid' (and test your kernel with CONFIG_KASAN enabled of course).

Dmitry