Re: [Intel-wired-lan] [PATCH][next] ixgbe: Fix out-of-bounds warning in ixgbe_host_interface_command()

2021-03-17 Thread Gustavo A. R. Silva 



On 3/17/21 15:10, Jann Horn wrote:
> On Wed, Mar 17, 2021 at 9:04 PM Gustavo A. R. Silva
>  wrote:
>> On 3/17/21 13:57, Jann Horn wrote:
>> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c 
>> b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
>> index 62ddb452f862..bff3dc1af702 100644
>> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
>> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
>> @@ -3679,7 +3679,7 @@ s32 ixgbe_host_interface_command(struct ixgbe_hw 
>> *hw, void *buffer,
>> u32 hdr_size = sizeof(struct ixgbe_hic_hdr);
>> union {
>> struct ixgbe_hic_hdr hdr;
>> -   u32 u32arr[1];
>> +   u32 *u32arr;
>> } *bp = buffer;
>> u16 buf_len, dword_len;
>> s32 status;
>
> This looks bogus. An array is inline, a pointer points elsewhere -
> they're not interchangeable.

 Yep; but in this case these are the only places in the code where _u32arr_ 
 is
 being used:

 3707 /* first pull in the header so we know the buffer length */
 3708 for (bi = 0; bi < dword_len; bi++) {
 3709 bp->u32arr[bi] = IXGBE_READ_REG_ARRAY(hw, 
 IXGBE_FLEX_MNG, bi);
 3710 le32_to_cpus(>u32arr[bi]);
 3711 }
>>>
>>> So now line 3709 means: Read a pointer from bp->u32arr (the value
>>> being read from there is not actually a valid pointer), and write to
>>> that pointer at offset `bi`. I don't see how that line could execute
>>> without crashing.
>>
>> Yeah; you're right. I see my confusion now. Apparently, there is no escape
>> from allocating heap memory to fix this issue, as I was proposing in my
>> last email.
> 
> Why? Can't you do something like this?

Yep; it seems you're right. I was thinking in terms of a flexible array. Also,
I think I needed more coffee in my system this morning and I need to stop
working after midnight. :)

I'll send a proper patch for this, shortly. I'll add your Proposed-by
and Co-developed-by tags to the changelog text.

Thanks a lot for the feedback. I really appreciate it. :)
--
Gustavo


> 
> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
> b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
> index 62ddb452f862..768fa124105b 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
> @@ -3677,10 +3677,8 @@ s32 ixgbe_host_interface_command(struct
> ixgbe_hw *hw, void *buffer,
>  bool return_data)
>  {
> u32 hdr_size = sizeof(struct ixgbe_hic_hdr);
> -   union {
> -   struct ixgbe_hic_hdr hdr;
> -   u32 u32arr[1];
> -   } *bp = buffer;
> +   u32 *bp = buffer;
> +   struct ixgbe_hic_hdr hdr;
> u16 buf_len, dword_len;
> s32 status;
> u32 bi;
> @@ -3706,12 +3704,13 @@ s32 ixgbe_host_interface_command(struct
> ixgbe_hw *hw, void *buffer,
> 
> /* first pull in the header so we know the buffer length */
> for (bi = 0; bi < dword_len; bi++) {
> -   bp->u32arr[bi] = IXGBE_READ_REG_ARRAY(hw, IXGBE_FLEX_MNG, bi);
> -   le32_to_cpus(>u32arr[bi]);
> +   bp[bi] = IXGBE_READ_REG_ARRAY(hw, IXGBE_FLEX_MNG, bi);
> +   le32_to_cpus([bi]);
> }
> 
> /* If there is any thing in data position pull it in */
> -   buf_len = bp->hdr.buf_len;
> +   memcpy(, bp, sizeof(hdr));
> +   buf_len = hdr.buf_len;
> if (!buf_len)
> goto rel_out;
> 
> @@ -3726,8 +3725,8 @@ s32 ixgbe_host_interface_command(struct ixgbe_hw
> *hw, void *buffer,
> 
> /* Pull in the rest of the buffer (bi is where we left off) */
> for (; bi <= dword_len; bi++) {
> -   bp->u32arr[bi] = IXGBE_READ_REG_ARRAY(hw, IXGBE_FLEX_MNG, bi);
> -   le32_to_cpus(>u32arr[bi]);
> +   bp[bi] = IXGBE_READ_REG_ARRAY(hw, IXGBE_FLEX_MNG, bi);
> +   le32_to_cpus([bi]);
> }
> 
>  rel_out:
>

Re: [Intel-wired-lan] [PATCH][next] ixgbe: Fix out-of-bounds warning in ixgbe_host_interface_command()

2021-03-17 Thread Gustavo A. R. Silva 



On 3/17/21 13:57, Jann Horn wrote:

 diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c 
 b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
 index 62ddb452f862..bff3dc1af702 100644
 --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
 +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
 @@ -3679,7 +3679,7 @@ s32 ixgbe_host_interface_command(struct ixgbe_hw 
 *hw, void *buffer,
 u32 hdr_size = sizeof(struct ixgbe_hic_hdr);
 union {
 struct ixgbe_hic_hdr hdr;
 -   u32 u32arr[1];
 +   u32 *u32arr;
 } *bp = buffer;
 u16 buf_len, dword_len;
 s32 status;
>>>
>>> This looks bogus. An array is inline, a pointer points elsewhere -
>>> they're not interchangeable.
>>
>> Yep; but in this case these are the only places in the code where _u32arr_ is
>> being used:
>>
>> 3707 /* first pull in the header so we know the buffer length */
>> 3708 for (bi = 0; bi < dword_len; bi++) {
>> 3709 bp->u32arr[bi] = IXGBE_READ_REG_ARRAY(hw, 
>> IXGBE_FLEX_MNG, bi);
>> 3710 le32_to_cpus(>u32arr[bi]);
>> 3711 }
> 
> So now line 3709 means: Read a pointer from bp->u32arr (the value
> being read from there is not actually a valid pointer), and write to
> that pointer at offset `bi`. I don't see how that line could execute
> without crashing.

Yeah; you're right. I see my confusion now. Apparently, there is no escape
from allocating heap memory to fix this issue, as I was proposing in my
last email.

I really appreciate the feedback. Thanks!
--
Gustavo

Re: [Intel-wired-lan] [PATCH][next] ixgbe: Fix out-of-bounds warning in ixgbe_host_interface_command()

2021-03-17 Thread Jann Horn 
On Wed, Mar 17, 2021 at 9:04 PM Gustavo A. R. Silva
 wrote:
> On 3/17/21 13:57, Jann Horn wrote:
>  diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c 
>  b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
>  index 62ddb452f862..bff3dc1af702 100644
>  --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
>  +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
>  @@ -3679,7 +3679,7 @@ s32 ixgbe_host_interface_command(struct ixgbe_hw 
>  *hw, void *buffer,
>  u32 hdr_size = sizeof(struct ixgbe_hic_hdr);
>  union {
>  struct ixgbe_hic_hdr hdr;
>  -   u32 u32arr[1];
>  +   u32 *u32arr;
>  } *bp = buffer;
>  u16 buf_len, dword_len;
>  s32 status;
> >>>
> >>> This looks bogus. An array is inline, a pointer points elsewhere -
> >>> they're not interchangeable.
> >>
> >> Yep; but in this case these are the only places in the code where _u32arr_ 
> >> is
> >> being used:
> >>
> >> 3707 /* first pull in the header so we know the buffer length */
> >> 3708 for (bi = 0; bi < dword_len; bi++) {
> >> 3709 bp->u32arr[bi] = IXGBE_READ_REG_ARRAY(hw, 
> >> IXGBE_FLEX_MNG, bi);
> >> 3710 le32_to_cpus(>u32arr[bi]);
> >> 3711 }
> >
> > So now line 3709 means: Read a pointer from bp->u32arr (the value
> > being read from there is not actually a valid pointer), and write to
> > that pointer at offset `bi`. I don't see how that line could execute
> > without crashing.
>
> Yeah; you're right. I see my confusion now. Apparently, there is no escape
> from allocating heap memory to fix this issue, as I was proposing in my
> last email.

Why? Can't you do something like this?

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
index 62ddb452f862..768fa124105b 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
@@ -3677,10 +3677,8 @@ s32 ixgbe_host_interface_command(struct
ixgbe_hw *hw, void *buffer,
 bool return_data)
 {
u32 hdr_size = sizeof(struct ixgbe_hic_hdr);
-   union {
-   struct ixgbe_hic_hdr hdr;
-   u32 u32arr[1];
-   } *bp = buffer;
+   u32 *bp = buffer;
+   struct ixgbe_hic_hdr hdr;
u16 buf_len, dword_len;
s32 status;
u32 bi;
@@ -3706,12 +3704,13 @@ s32 ixgbe_host_interface_command(struct
ixgbe_hw *hw, void *buffer,

/* first pull in the header so we know the buffer length */
for (bi = 0; bi < dword_len; bi++) {
-   bp->u32arr[bi] = IXGBE_READ_REG_ARRAY(hw, IXGBE_FLEX_MNG, bi);
-   le32_to_cpus(>u32arr[bi]);
+   bp[bi] = IXGBE_READ_REG_ARRAY(hw, IXGBE_FLEX_MNG, bi);
+   le32_to_cpus([bi]);
}

/* If there is any thing in data position pull it in */
-   buf_len = bp->hdr.buf_len;
+   memcpy(, bp, sizeof(hdr));
+   buf_len = hdr.buf_len;
if (!buf_len)
goto rel_out;

@@ -3726,8 +3725,8 @@ s32 ixgbe_host_interface_command(struct ixgbe_hw
*hw, void *buffer,

/* Pull in the rest of the buffer (bi is where we left off) */
for (; bi <= dword_len; bi++) {
-   bp->u32arr[bi] = IXGBE_READ_REG_ARRAY(hw, IXGBE_FLEX_MNG, bi);
-   le32_to_cpus(>u32arr[bi]);
+   bp[bi] = IXGBE_READ_REG_ARRAY(hw, IXGBE_FLEX_MNG, bi);
+   le32_to_cpus([bi]);
}

 rel_out:

Re: [Intel-wired-lan] [PATCH][next] ixgbe: Fix out-of-bounds warning in ixgbe_host_interface_command()

2021-03-17 Thread Jann Horn 
On Wed, Mar 17, 2021 at 7:27 PM Gustavo A. R. Silva
 wrote:
> On 3/17/21 12:11, Jann Horn wrote:
> > On Wed, Mar 17, 2021 at 8:43 AM Gustavo A. R. Silva
> >  wrote:
> >> Fix the following out-of-bounds warning by replacing the one-element
> >> array in an anonymous union with a pointer:
> >>
> >>   CC [M]  drivers/net/ethernet/intel/ixgbe/ixgbe_common.o
> >> drivers/net/ethernet/intel/ixgbe/ixgbe_common.c: In function 
> >> ‘ixgbe_host_interface_command’:
> >> drivers/net/ethernet/intel/ixgbe/ixgbe_common.c:3729:13: warning: array 
> >> subscript 1 is above array bounds of ‘u32[1]’ {aka ‘unsigned int[1]’} 
> >> [-Warray-bounds]
> >>  3729 |   bp->u32arr[bi] = IXGBE_READ_REG_ARRAY(hw, IXGBE_FLEX_MNG, bi);
> >>   |   ~~^~~~
> >> drivers/net/ethernet/intel/ixgbe/ixgbe_common.c:3682:7: note: while 
> >> referencing ‘u32arr’
> >>  3682 |   u32 u32arr[1];
> >>   |   ^~
> >>
> >> This helps with the ongoing efforts to globally enable -Warray-bounds.
> >>
> >> Notice that, the usual approach to fix these sorts of issues is to
> >> replace the one-element array with a flexible-array member. However,
> >> flexible arrays should not be used in unions. That, together with the
> >> fact that the array notation is not being affected in any ways, is why
> >> the pointer approach was chosen in this case.
> >>
> >> Link: https://github.com/KSPP/linux/issues/109
> >> Signed-off-by: Gustavo A. R. Silva 
> >> ---
> >>  drivers/net/ethernet/intel/ixgbe/ixgbe_common.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c 
> >> b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
> >> index 62ddb452f862..bff3dc1af702 100644
> >> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
> >> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
> >> @@ -3679,7 +3679,7 @@ s32 ixgbe_host_interface_command(struct ixgbe_hw 
> >> *hw, void *buffer,
> >> u32 hdr_size = sizeof(struct ixgbe_hic_hdr);
> >> union {
> >> struct ixgbe_hic_hdr hdr;
> >> -   u32 u32arr[1];
> >> +   u32 *u32arr;
> >> } *bp = buffer;
> >> u16 buf_len, dword_len;
> >> s32 status;
> >
> > This looks bogus. An array is inline, a pointer points elsewhere -
> > they're not interchangeable.
>
> Yep; but in this case these are the only places in the code where _u32arr_ is
> being used:
>
> 3707 /* first pull in the header so we know the buffer length */
> 3708 for (bi = 0; bi < dword_len; bi++) {
> 3709 bp->u32arr[bi] = IXGBE_READ_REG_ARRAY(hw, 
> IXGBE_FLEX_MNG, bi);
> 3710 le32_to_cpus(>u32arr[bi]);
> 3711 }

So now line 3709 means: Read a pointer from bp->u32arr (the value
being read from there is not actually a valid pointer), and write to
that pointer at offset `bi`. I don't see how that line could execute
without crashing.

Re: [Intel-wired-lan] [PATCH][next] ixgbe: Fix out-of-bounds warning in ixgbe_host_interface_command()

2021-03-17 Thread Gustavo A. R. Silva 
Hi Jann,

Please, see my comments below...

On 3/17/21 12:11, Jann Horn wrote:
> On Wed, Mar 17, 2021 at 8:43 AM Gustavo A. R. Silva
>  wrote:
>> Fix the following out-of-bounds warning by replacing the one-element
>> array in an anonymous union with a pointer:
>>
>>   CC [M]  drivers/net/ethernet/intel/ixgbe/ixgbe_common.o
>> drivers/net/ethernet/intel/ixgbe/ixgbe_common.c: In function 
>> ‘ixgbe_host_interface_command’:
>> drivers/net/ethernet/intel/ixgbe/ixgbe_common.c:3729:13: warning: array 
>> subscript 1 is above array bounds of ‘u32[1]’ {aka ‘unsigned int[1]’} 
>> [-Warray-bounds]
>>  3729 |   bp->u32arr[bi] = IXGBE_READ_REG_ARRAY(hw, IXGBE_FLEX_MNG, bi);
>>   |   ~~^~~~
>> drivers/net/ethernet/intel/ixgbe/ixgbe_common.c:3682:7: note: while 
>> referencing ‘u32arr’
>>  3682 |   u32 u32arr[1];
>>   |   ^~
>>
>> This helps with the ongoing efforts to globally enable -Warray-bounds.
>>
>> Notice that, the usual approach to fix these sorts of issues is to
>> replace the one-element array with a flexible-array member. However,
>> flexible arrays should not be used in unions. That, together with the
>> fact that the array notation is not being affected in any ways, is why
>> the pointer approach was chosen in this case.
>>
>> Link: https://github.com/KSPP/linux/issues/109
>> Signed-off-by: Gustavo A. R. Silva 
>> ---
>>  drivers/net/ethernet/intel/ixgbe/ixgbe_common.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c 
>> b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
>> index 62ddb452f862..bff3dc1af702 100644
>> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
>> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
>> @@ -3679,7 +3679,7 @@ s32 ixgbe_host_interface_command(struct ixgbe_hw *hw, 
>> void *buffer,
>> u32 hdr_size = sizeof(struct ixgbe_hic_hdr);
>> union {
>> struct ixgbe_hic_hdr hdr;
>> -   u32 u32arr[1];
>> +   u32 *u32arr;
>> } *bp = buffer;
>> u16 buf_len, dword_len;
>> s32 status;
> 
> This looks bogus. An array is inline, a pointer points elsewhere -
> they're not interchangeable.

Yep; but in this case these are the only places in the code where _u32arr_ is
being used:

3707 /* first pull in the header so we know the buffer length */
3708 for (bi = 0; bi < dword_len; bi++) {
3709 bp->u32arr[bi] = IXGBE_READ_REG_ARRAY(hw, IXGBE_FLEX_MNG, 
bi);
3710 le32_to_cpus(>u32arr[bi]);
3711 }

3727 /* Pull in the rest of the buffer (bi is where we left off) */
3728 for (; bi <= dword_len; bi++) {
3729 bp->u32arr[bi] = IXGBE_READ_REG_ARRAY(hw, IXGBE_FLEX_MNG, 
bi);
3730 le32_to_cpus(>u32arr[bi]);
3731 }

I think it is safe to turn _u32arra_ into a pointer and continue using the 
array notation
in this particular case.

I also mention this in the changelog text:

"Notice that, the usual approach to fix these sorts of issues is to
replace the one-element array with a flexible-array member. However,
flexible arrays should not be used in unions. That, together with the
fact that the array notation is not being affected in any ways, is why
the pointer approach was chosen in this case."

Do you see any particular problem with this in the current code?

Another solution for this would be as follows:

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c 
b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
index 62ddb452f862..3ad95281d790 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
@@ -3677,10 +3677,11 @@ s32 ixgbe_host_interface_command(struct ixgbe_hw *hw, 
void *buffer,
 bool return_data)
 {
u32 hdr_size = sizeof(struct ixgbe_hic_hdr);
-   union {
-   struct ixgbe_hic_hdr hdr;
-   u32 u32arr[1];
-   } *bp = buffer;
+   struct ixgbe_hic_hdr *bp_hdr = buffer;
+   struct {
+   size_t len;
+   u32 u32arr[];
+   } *bp;
u16 buf_len, dword_len;
s32 status;
u32 bi;
@@ -3704,6 +3705,9 @@ s32 ixgbe_host_interface_command(struct ixgbe_hw *hw, 
void *buffer,
/* Calculate length in DWORDs */
dword_len = hdr_size >> 2;

+   bp = kmalloc(struct_size(bp, u32arr, dword_len), GFP_KERNEL);
+   bp->len = dword_len;
+   memcpy(bp->u32arr, buffer, flex_array_size(bp, u32arr, bp->len));
/* first pull in the header so we know the buffer length */
for (bi = 0; bi < dword_len; bi++) {
bp->u32arr[bi] = IXGBE_READ_REG_ARRAY(hw, IXGBE_FLEX_MNG, bi);
@@ -3711,7 +3715,7 @@ s32 ixgbe_host_interface_command(struct ixgbe_hw *hw, 
void *buffer,
}

/* If there is any thing in data position pull it in */
-   buf_len = bp->hdr.buf_len;
+   buf_len =

Re: [PATCH][next] ixgbe: Fix out-of-bounds warning in ixgbe_host_interface_command()

2021-03-17 Thread Jann Horn 
On Wed, Mar 17, 2021 at 8:43 AM Gustavo A. R. Silva
 wrote:
> Fix the following out-of-bounds warning by replacing the one-element
> array in an anonymous union with a pointer:
>
>   CC [M]  drivers/net/ethernet/intel/ixgbe/ixgbe_common.o
> drivers/net/ethernet/intel/ixgbe/ixgbe_common.c: In function 
> ‘ixgbe_host_interface_command’:
> drivers/net/ethernet/intel/ixgbe/ixgbe_common.c:3729:13: warning: array 
> subscript 1 is above array bounds of ‘u32[1]’ {aka ‘unsigned int[1]’} 
> [-Warray-bounds]
>  3729 |   bp->u32arr[bi] = IXGBE_READ_REG_ARRAY(hw, IXGBE_FLEX_MNG, bi);
>   |   ~~^~~~
> drivers/net/ethernet/intel/ixgbe/ixgbe_common.c:3682:7: note: while 
> referencing ‘u32arr’
>  3682 |   u32 u32arr[1];
>   |   ^~
>
> This helps with the ongoing efforts to globally enable -Warray-bounds.
>
> Notice that, the usual approach to fix these sorts of issues is to
> replace the one-element array with a flexible-array member. However,
> flexible arrays should not be used in unions. That, together with the
> fact that the array notation is not being affected in any ways, is why
> the pointer approach was chosen in this case.
>
> Link: https://github.com/KSPP/linux/issues/109
> Signed-off-by: Gustavo A. R. Silva 
> ---
>  drivers/net/ethernet/intel/ixgbe/ixgbe_common.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c 
> b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
> index 62ddb452f862..bff3dc1af702 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
> @@ -3679,7 +3679,7 @@ s32 ixgbe_host_interface_command(struct ixgbe_hw *hw, 
> void *buffer,
> u32 hdr_size = sizeof(struct ixgbe_hic_hdr);
> union {
> struct ixgbe_hic_hdr hdr;
> -   u32 u32arr[1];
> +   u32 *u32arr;
> } *bp = buffer;
> u16 buf_len, dword_len;
> s32 status;

This looks bogus. An array is inline, a pointer points elsewhere -
they're not interchangeable.

[PATCH][next] ixgbe: Fix out-of-bounds warning in ixgbe_host_interface_command()

2021-03-17 Thread Gustavo A. R. Silva 
Fix the following out-of-bounds warning by replacing the one-element
array in an anonymous union with a pointer:

  CC [M]  drivers/net/ethernet/intel/ixgbe/ixgbe_common.o
drivers/net/ethernet/intel/ixgbe/ixgbe_common.c: In function 
‘ixgbe_host_interface_command’:
drivers/net/ethernet/intel/ixgbe/ixgbe_common.c:3729:13: warning: array 
subscript 1 is above array bounds of ‘u32[1]’ {aka ‘unsigned int[1]’} 
[-Warray-bounds]
 3729 |   bp->u32arr[bi] = IXGBE_READ_REG_ARRAY(hw, IXGBE_FLEX_MNG, bi);
  |   ~~^~~~
drivers/net/ethernet/intel/ixgbe/ixgbe_common.c:3682:7: note: while referencing 
‘u32arr’
 3682 |   u32 u32arr[1];
  |   ^~

This helps with the ongoing efforts to globally enable -Warray-bounds.

Notice that, the usual approach to fix these sorts of issues is to
replace the one-element array with a flexible-array member. However,
flexible arrays should not be used in unions. That, together with the
fact that the array notation is not being affected in any ways, is why
the pointer approach was chosen in this case.

Link: https://github.com/KSPP/linux/issues/109
Signed-off-by: Gustavo A. R. Silva 
---
 drivers/net/ethernet/intel/ixgbe/ixgbe_common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c 
b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
index 62ddb452f862..bff3dc1af702 100644
--- a/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
+++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_common.c
@@ -3679,7 +3679,7 @@ s32 ixgbe_host_interface_command(struct ixgbe_hw *hw, 
void *buffer,
u32 hdr_size = sizeof(struct ixgbe_hic_hdr);
union {
struct ixgbe_hic_hdr hdr;
-   u32 u32arr[1];
+   u32 *u32arr;
} *bp = buffer;
u16 buf_len, dword_len;
s32 status;
-- 
2.27.0