[PATCH] libbpf: Fix uninitialized warning in btf_dump_dump_type_data

[PATCH] libbpf: Fix uninitialized warning in btf_dump_dump_type_data

[David Michael]

GCC 11.3.0 fails to compile btf_dump.c due to the following error,
which seems to originate in btf_dump_struct_data where the returned
value would be uninitialized if btf_vlen returns zero.

btf_dump.c: In function ‘btf_dump_dump_type_data’:
btf_dump.c:2363:12: error: ‘err’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
 2363 |         if (err < 0)
      |            ^

Fixes: 43174f0d4597 ("libbpf: Silence uninitialized warning/error in btf_dump_dump_type_data")
Signed-off-by: David Michael <fedora.dm0@gmail.com>
---

Hi,

I encountered this build failure when using Gentoo's hardened profile to
build sys-kernel/gentoo-kernel (at least some 5.19 and 6.0 versions).
The following patch fixes it.  Can this be applied?

Thanks.

David

 tools/lib/bpf/btf_dump.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c
index 12f7039e0..e9f849d82 100644
--- a/tools/lib/bpf/btf_dump.c
+++ b/tools/lib/bpf/btf_dump.c
@@ -1989,7 +1989,7 @@ static int btf_dump_struct_data(struct btf_dump *d,
 {
 	const struct btf_member *m = btf_members(t);
 	__u16 n = btf_vlen(t);
-	int i, err;
+	int i, err = 0;
 
 	/* note that we increment depth before calling btf_dump_print() below;
 	 * this is intentional.  btf_dump_data_newline() will not print a
-- 
2.38.1

Re: [PATCH] libbpf: Fix uninitialized warning in btf_dump_dump_type_data

[sdf]

On 11/13, David Michael wrote:
> GCC 11.3.0 fails to compile btf_dump.c due to the following error,
> which seems to originate in btf_dump_struct_data where the returned
> value would be uninitialized if btf_vlen returns zero.

> btf_dump.c: In function ‘btf_dump_dump_type_data’:
> btf_dump.c:2363:12: error: ‘err’ may be used uninitialized in this  
> function [-Werror=maybe-uninitialized]
>   2363 |         if (err < 0)
>        |            ^

> Fixes: 43174f0d4597 ("libbpf: Silence uninitialized warning/error in  
> btf_dump_dump_type_data")

Probably better to reference the original patch?
Fixes: 920d16af9b42 ("libbpf: BTF dumper support for typed data")

Acked-by: Stanislav Fomichev <sdf@google.com>

> Signed-off-by: David Michael <fedora.dm0@gmail.com>
> ---

> Hi,

> I encountered this build failure when using Gentoo's hardened profile to
> build sys-kernel/gentoo-kernel (at least some 5.19 and 6.0 versions).
> The following patch fixes it.  Can this be applied?

> Thanks.

> David

>   tools/lib/bpf/btf_dump.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)

> diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c
> index 12f7039e0..e9f849d82 100644
> --- a/tools/lib/bpf/btf_dump.c
> +++ b/tools/lib/bpf/btf_dump.c
> @@ -1989,7 +1989,7 @@ static int btf_dump_struct_data(struct btf_dump *d,
>   {
>   	const struct btf_member *m = btf_members(t);
>   	__u16 n = btf_vlen(t);
> -	int i, err;
> +	int i, err = 0;

>   	/* note that we increment depth before calling btf_dump_print() below;
>   	 * this is intentional.  btf_dump_data_newline() will not print a
> --
> 2.38.1

Re: [PATCH] libbpf: Fix uninitialized warning in btf_dump_dump_type_data

[Alan Maguire]

On 14/11/2022 17:21, sdf@google.com wrote:
> On 11/13, David Michael wrote:
>> GCC 11.3.0 fails to compile btf_dump.c due to the following error,
>> which seems to originate in btf_dump_struct_data where the returned
>> value would be uninitialized if btf_vlen returns zero.
> 
>> btf_dump.c: In function ‘btf_dump_dump_type_data’:
>> btf_dump.c:2363:12: error: ‘err’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
>>   2363 |         if (err < 0)
>>        |            ^
> 
>> Fixes: 43174f0d4597 ("libbpf: Silence uninitialized warning/error in btf_dump_dump_type_data")
> 
> Probably better to reference the original patch?
> Fixes: 920d16af9b42 ("libbpf: BTF dumper support for typed data")
> 
> Acked-by: Stanislav Fomichev <sdf@google.com>
>

Acked-by: Alan Maguire <alan.maguire@oracle.com>

Thanks for fixing!

>> Signed-off-by: David Michael <fedora.dm0@gmail.com>
>> ---
> 
>> Hi,
> 
>> I encountered this build failure when using Gentoo's hardened profile to
>> build sys-kernel/gentoo-kernel (at least some 5.19 and 6.0 versions).
>> The following patch fixes it.  Can this be applied?
> 
>> Thanks.
> 
>> David
> 
>>   tools/lib/bpf/btf_dump.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
>> diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c
>> index 12f7039e0..e9f849d82 100644
>> --- a/tools/lib/bpf/btf_dump.c
>> +++ b/tools/lib/bpf/btf_dump.c
>> @@ -1989,7 +1989,7 @@ static int btf_dump_struct_data(struct btf_dump *d,
>>   {
>>       const struct btf_member *m = btf_members(t);
>>       __u16 n = btf_vlen(t);
>> -    int i, err;
>> +    int i, err = 0;
> 
>>       /* note that we increment depth before calling btf_dump_print() below;
>>        * this is intentional.  btf_dump_data_newline() will not print a
>> -- 
>> 2.38.1

Re: [PATCH] libbpf: Fix uninitialized warning in btf_dump_dump_type_data

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Daniel Borkmann <daniel@iogearbox.net>:

On Sun, 13 Nov 2022 15:52:17 -0500 you wrote:
> GCC 11.3.0 fails to compile btf_dump.c due to the following error,
> which seems to originate in btf_dump_struct_data where the returned
> value would be uninitialized if btf_vlen returns zero.
> 
> btf_dump.c: In function ‘btf_dump_dump_type_data’:
> btf_dump.c:2363:12: error: ‘err’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
>  2363 |         if (err < 0)
>       |            ^
> 
> [...]

Here is the summary with links:
  - libbpf: Fix uninitialized warning in btf_dump_dump_type_data
    https://git.kernel.org/bpf/bpf-next/c/dfd0afbf151d

You are awesome, thank you!
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