* [PATCH v2] md/bcache: Mark __nonstring look-up table
@ 2025-04-18 20:21 Kees Cook
2025-04-19 3:55 ` Coly Li
0 siblings, 1 reply; 5+ messages in thread
From: Kees Cook @ 2025-04-18 20:21 UTC (permalink / raw)
To: Coly Li
Cc: Kees Cook, Kent Overstreet, Ard Biesheuvel, linux-bcache,
linux-kernel, linux-hardening
GCC 15's new -Wunterminated-string-initialization notices that the 16
character lookup table "zero_uuid" (which is not used as a C-String)
needs to be marked as "nonstring":
drivers/md/bcache/super.c: In function 'uuid_find_empty':
drivers/md/bcache/super.c:549:43: warning: initializer-string for array of 'char' truncates NUL terminator but destination lacks 'nonstring' attribute (17 chars into 16 available) [-Wunterminated-string-initialization]
549 | static const char zero_uuid[16] = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Add the annotation (since it is not used as a C-String), and switch the
initializer to an array of bytes.
Signed-off-by: Kees Cook <kees@kernel.org>
---
v2: use byte array initializer (colyli)
v1: https://lore.kernel.org/all/20250416220135.work.394-kees@kernel.org/
Cc: Coly Li <colyli@kernel.org>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: linux-bcache@vger.kernel.org
---
drivers/md/bcache/super.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index e42f1400cea9..a76ce92502ed 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -546,7 +546,8 @@ static struct uuid_entry *uuid_find(struct cache_set *c, const char *uuid)
static struct uuid_entry *uuid_find_empty(struct cache_set *c)
{
- static const char zero_uuid[16] = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
+ static const char zero_uuid[] __nonstring =
+ { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
return uuid_find(c, zero_uuid);
}
--
2.34.1
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH v2] md/bcache: Mark __nonstring look-up table
2025-04-18 20:21 [PATCH v2] md/bcache: Mark __nonstring look-up table Kees Cook
@ 2025-04-19 3:55 ` Coly Li
2025-05-08 3:01 ` Coly Li
0 siblings, 1 reply; 5+ messages in thread
From: Coly Li @ 2025-04-19 3:55 UTC (permalink / raw)
To: Kees Cook
Cc: Coly Li, Kent Overstreet, Ard Biesheuvel, linux-bcache,
linux-kernel, linux-hardening
> 2025年4月19日 04:21，Kees Cook <kees@kernel.org> 写道：
>
> GCC 15's new -Wunterminated-string-initialization notices that the 16
> character lookup table "zero_uuid" (which is not used as a C-String)
> needs to be marked as "nonstring":
>
> drivers/md/bcache/super.c: In function 'uuid_find_empty':
> drivers/md/bcache/super.c:549:43: warning: initializer-string for array of 'char' truncates NUL terminator but destination lacks 'nonstring' attribute (17 chars into 16 available) [-Wunterminated-string-initialization]
> 549 | static const char zero_uuid[16] = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Add the annotation (since it is not used as a C-String), and switch the
> initializer to an array of bytes.
>
> Signed-off-by: Kees Cook <kees@kernel.org>
> ---
> v2: use byte array initializer (colyli)
> v1: https://lore.kernel.org/all/20250416220135.work.394-kees@kernel.org/
> Cc: Coly Li <colyli@kernel.org>
> Cc: Kent Overstreet <kent.overstreet@linux.dev>
> Cc: Ard Biesheuvel <ardb@kernel.org>
> Cc: linux-bcache@vger.kernel.org
> ---
> drivers/md/bcache/super.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
> index e42f1400cea9..a76ce92502ed 100644
> --- a/drivers/md/bcache/super.c
> +++ b/drivers/md/bcache/super.c
> @@ -546,7 +546,8 @@ static struct uuid_entry *uuid_find(struct cache_set *c, const char *uuid)
>
> static struct uuid_entry *uuid_find_empty(struct cache_set *c)
> {
> - static const char zero_uuid[16] = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
> + static const char zero_uuid[] __nonstring =
I notice zero_uuid[16] changes to zero_uuid[], then the element number information is removed.
Is it OK for GCC 15 to only add __nonstring and keep zero_uuid[16]?
Thanks.
Coly Li
> + { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
>
> return uuid_find(c, zero_uuid);
> }
> --
> 2.34.1
>
>
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH v2] md/bcache: Mark __nonstring look-up table
2025-04-19 3:55 ` Coly Li
@ 2025-05-08 3:01 ` Coly Li
2025-05-08 15:58 ` Kees Cook
0 siblings, 1 reply; 5+ messages in thread
From: Coly Li @ 2025-05-08 3:01 UTC (permalink / raw)
To: Kees Cook
Cc: Coly Li, Kent Overstreet, Ard Biesheuvel, linux-bcache,
linux-kernel, linux-hardening
> 2025年4月19日 11:55，Coly Li <i@coly.li> 写道：
>
>
>
>> 2025年4月19日 04:21，Kees Cook <kees@kernel.org> 写道：
>>
>> GCC 15's new -Wunterminated-string-initialization notices that the 16
>> character lookup table "zero_uuid" (which is not used as a C-String)
>> needs to be marked as "nonstring":
>>
>> drivers/md/bcache/super.c: In function 'uuid_find_empty':
>> drivers/md/bcache/super.c:549:43: warning: initializer-string for array of 'char' truncates NUL terminator but destination lacks 'nonstring' attribute (17 chars into 16 available) [-Wunterminated-string-initialization]
>> 549 | static const char zero_uuid[16] = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
>> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> Add the annotation (since it is not used as a C-String), and switch the
>> initializer to an array of bytes.
>>
>> Signed-off-by: Kees Cook <kees@kernel.org>
>> ---
>> v2: use byte array initializer (colyli)
>> v1: https://lore.kernel.org/all/20250416220135.work.394-kees@kernel.org/
>> Cc: Coly Li <colyli@kernel.org>
>> Cc: Kent Overstreet <kent.overstreet@linux.dev>
>> Cc: Ard Biesheuvel <ardb@kernel.org>
>> Cc: linux-bcache@vger.kernel.org
>> ---
>> drivers/md/bcache/super.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
>> index e42f1400cea9..a76ce92502ed 100644
>> --- a/drivers/md/bcache/super.c
>> +++ b/drivers/md/bcache/super.c
>> @@ -546,7 +546,8 @@ static struct uuid_entry *uuid_find(struct cache_set *c, const char *uuid)
>>
>> static struct uuid_entry *uuid_find_empty(struct cache_set *c)
>> {
>> - static const char zero_uuid[16] = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
>> + static const char zero_uuid[] __nonstring =
>
Hi Kees,
> I notice zero_uuid[16] changes to zero_uuid[], then the element number information is removed.
>
> Is it OK for GCC 15 to only add __nonstring and keep zero_uuid[16]?
Ping ?
You are expert here, I need your opinion.
Thanks.
Coly Li
>> + { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
>>
>> return uuid_find(c, zero_uuid);
>> }
>> --
>> 2.34.1
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH v2] md/bcache: Mark __nonstring look-up table
2025-05-08 3:01 ` Coly Li
@ 2025-05-08 15:58 ` Kees Cook
2025-05-08 15:59 ` Coly Li
0 siblings, 1 reply; 5+ messages in thread
From: Kees Cook @ 2025-05-08 15:58 UTC (permalink / raw)
To: Coly Li
Cc: Coly Li, Kent Overstreet, Ard Biesheuvel, linux-bcache,
linux-kernel, linux-hardening
On Thu, May 08, 2025 at 11:01:34AM +0800, Coly Li wrote:
>
> > 2025年4月19日 11:55，Coly Li <i@coly.li> 写道：
> >
> >
> >
> >> 2025年4月19日 04:21，Kees Cook <kees@kernel.org> 写道：
> >>
> >> GCC 15's new -Wunterminated-string-initialization notices that the 16
> >> character lookup table "zero_uuid" (which is not used as a C-String)
> >> needs to be marked as "nonstring":
> >>
> >> drivers/md/bcache/super.c: In function 'uuid_find_empty':
> >> drivers/md/bcache/super.c:549:43: warning: initializer-string for array of 'char' truncates NUL terminator but destination lacks 'nonstring' attribute (17 chars into 16 available) [-Wunterminated-string-initialization]
> >> 549 | static const char zero_uuid[16] = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
> >> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >>
> >> Add the annotation (since it is not used as a C-String), and switch the
> >> initializer to an array of bytes.
> >>
> >> Signed-off-by: Kees Cook <kees@kernel.org>
> >> ---
> >> v2: use byte array initializer (colyli)
> >> v1: https://lore.kernel.org/all/20250416220135.work.394-kees@kernel.org/
> >> Cc: Coly Li <colyli@kernel.org>
> >> Cc: Kent Overstreet <kent.overstreet@linux.dev>
> >> Cc: Ard Biesheuvel <ardb@kernel.org>
> >> Cc: linux-bcache@vger.kernel.org
> >> ---
> >> drivers/md/bcache/super.c | 3 ++-
> >> 1 file changed, 2 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
> >> index e42f1400cea9..a76ce92502ed 100644
> >> --- a/drivers/md/bcache/super.c
> >> +++ b/drivers/md/bcache/super.c
> >> @@ -546,7 +546,8 @@ static struct uuid_entry *uuid_find(struct cache_set *c, const char *uuid)
> >>
> >> static struct uuid_entry *uuid_find_empty(struct cache_set *c)
> >> {
> >> - static const char zero_uuid[16] = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
> >> + static const char zero_uuid[] __nonstring =
> >
>
> Hi Kees,
>
> > I notice zero_uuid[16] changes to zero_uuid[], then the element number information is removed.
> >
> > Is it OK for GCC 15 to only add __nonstring and keep zero_uuid[16]?
Either way is fine. I can update the patch to use the "[16]" again if
you'd like?
-Kees
> Ping ?
>
> You are expert here, I need your opinion.
>
> Thanks.
>
> Coly Li
>
>
>
> >> + { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
> >>
> >> return uuid_find(c, zero_uuid);
> >> }
> >> --
> >> 2.34.1
>
>
--
Kees Cook
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH v2] md/bcache: Mark __nonstring look-up table
2025-05-08 15:58 ` Kees Cook
@ 2025-05-08 15:59 ` Coly Li
0 siblings, 0 replies; 5+ messages in thread
From: Coly Li @ 2025-05-08 15:59 UTC (permalink / raw)
To: Kees Cook
Cc: Coly Li, Kent Overstreet, Ard Biesheuvel, linux-bcache,
linux-kernel, linux-hardening
> 2025年5月8日 23:58，Kees Cook <kees@kernel.org> 写道：
>
> On Thu, May 08, 2025 at 11:01:34AM +0800, Coly Li wrote:
>>
>>> 2025年4月19日 11:55，Coly Li <i@coly.li> 写道：
>>>
>>>
>>>
>>>> 2025年4月19日 04:21，Kees Cook <kees@kernel.org> 写道：
>>>>
>>>> GCC 15's new -Wunterminated-string-initialization notices that the 16
>>>> character lookup table "zero_uuid" (which is not used as a C-String)
>>>> needs to be marked as "nonstring":
>>>>
>>>> drivers/md/bcache/super.c: In function 'uuid_find_empty':
>>>> drivers/md/bcache/super.c:549:43: warning: initializer-string for array of 'char' truncates NUL terminator but destination lacks 'nonstring' attribute (17 chars into 16 available) [-Wunterminated-string-initialization]
>>>> 549 | static const char zero_uuid[16] = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
>>>> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>>
>>>> Add the annotation (since it is not used as a C-String), and switch the
>>>> initializer to an array of bytes.
>>>>
>>>> Signed-off-by: Kees Cook <kees@kernel.org>
>>>> ---
>>>> v2: use byte array initializer (colyli)
>>>> v1: https://lore.kernel.org/all/20250416220135.work.394-kees@kernel.org/
>>>> Cc: Coly Li <colyli@kernel.org>
>>>> Cc: Kent Overstreet <kent.overstreet@linux.dev>
>>>> Cc: Ard Biesheuvel <ardb@kernel.org>
>>>> Cc: linux-bcache@vger.kernel.org
>>>> ---
>>>> drivers/md/bcache/super.c | 3 ++-
>>>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
>>>> index e42f1400cea9..a76ce92502ed 100644
>>>> --- a/drivers/md/bcache/super.c
>>>> +++ b/drivers/md/bcache/super.c
>>>> @@ -546,7 +546,8 @@ static struct uuid_entry *uuid_find(struct cache_set *c, const char *uuid)
>>>>
>>>> static struct uuid_entry *uuid_find_empty(struct cache_set *c)
>>>> {
>>>> - static const char zero_uuid[16] = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
>>>> + static const char zero_uuid[] __nonstring =
>>>
>>
>> Hi Kees,
>>
>>> I notice zero_uuid[16] changes to zero_uuid[], then the element number information is removed.
>>>
>>> Is it OK for GCC 15 to only add __nonstring and keep zero_uuid[16]?
>
> Either way is fine. I can update the patch to use the "[16]" again if
> you'd like?
>
Yes please. Thanks in advance.
Coly Li
>
>> Ping ?
>>
>> You are expert here, I need your opinion.
>>
>> Thanks.
>>
>> Coly Li
>>
>>
>>
>>>> + { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
>>>>
>>>> return uuid_find(c, zero_uuid);
>>>> }
>>>> --
>>>> 2.34.1
>>
>>
>
> --
> Kees Cook
^ permalink raw reply [flat|nested] 5+ messages in thread
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2025-04-18 20:21 [PATCH v2] md/bcache: Mark __nonstring look-up table Kees Cook
2025-04-19 3:55 ` Coly Li
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2025-05-08 15:58 ` Kees Cook
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