* [PATCH] libbpf: avoid possible use of uninitialized mod_len
@ 2025-07-29 9:45 Achill Gilgenast
2025-07-29 16:17 ` Yonghong Song
0 siblings, 1 reply; 6+ messages in thread
From: Achill Gilgenast @ 2025-07-29 9:45 UTC (permalink / raw)
To: Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
Viktor Malik, bpf
Cc: linux-kernel, Achill Gilgenast, Martin KaFai Lau,
Eduard Zingerman, Song Liu, Yonghong Song, John Fastabend,
KP Singh, Stanislav Fomichev, Hao Luo, Jiri Olsa
If not fn_name, mod_len does never get initialized which fails now with
gcc15 on Alpine Linux edge:
libbpf.c: In function 'find_kernel_btf_id.constprop':
libbpf.c:10100:33: error: 'mod_len' may be used uninitialized [-Werror=maybe-uninitialized]
10100 | if (mod_name && strncmp(mod->name, mod_name, mod_len) != 0)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
libbpf.c:10070:21: note: 'mod_len' was declared here
10070 | int ret, i, mod_len;
| ^~~~~~~
Fixes: 8f8a024272f3 ("libbpf: support "module: Function" syntax for tracing programs")
Signed-off-by: Achill Gilgenast <fossdd@pwned.life>
---
tools/lib/bpf/libbpf.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index e067cb5776bd..fb4d92c5c339 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -10086,27 +10086,27 @@ static int libbpf_find_prog_btf_id(const char *name, __u32 attach_prog_fd, int t
btf__free(btf);
if (err <= 0) {
pr_warn("%s is not found in prog's BTF\n", name);
goto out;
}
out:
return err;
}
static int find_kernel_btf_id(struct bpf_object *obj, const char *attach_name,
enum bpf_attach_type attach_type,
int *btf_obj_fd, int *btf_type_id)
{
- int ret, i, mod_len;
+ int ret, i, mod_len = 0;
const char *fn_name, *mod_name = NULL;
fn_name = strchr(attach_name, ':');
if (fn_name) {
mod_name = attach_name;
mod_len = fn_name - mod_name;
fn_name++;
}
if (!mod_name || strncmp(mod_name, "vmlinux", mod_len) == 0) {
ret = find_attach_btf_id(obj->btf_vmlinux,
mod_name ? fn_name : attach_name,
attach_type);
--
2.50.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] libbpf: avoid possible use of uninitialized mod_len
2025-07-29 9:45 [PATCH] libbpf: avoid possible use of uninitialized mod_len Achill Gilgenast
@ 2025-07-29 16:17 ` Yonghong Song
2025-07-30 16:13 ` Eduard Zingerman
0 siblings, 1 reply; 6+ messages in thread
From: Yonghong Song @ 2025-07-29 16:17 UTC (permalink / raw)
To: Achill Gilgenast, Alexei Starovoitov, Daniel Borkmann,
Andrii Nakryiko, Viktor Malik, bpf
Cc: linux-kernel, Martin KaFai Lau, Eduard Zingerman, Song Liu,
John Fastabend, KP Singh, Stanislav Fomichev, Hao Luo, Jiri Olsa
On 7/29/25 2:45 AM, Achill Gilgenast wrote:
> If not fn_name, mod_len does never get initialized which fails now with
> gcc15 on Alpine Linux edge:
>
> libbpf.c: In function 'find_kernel_btf_id.constprop':
> libbpf.c:10100:33: error: 'mod_len' may be used uninitialized [-Werror=maybe-uninitialized]
> 10100 | if (mod_name && strncmp(mod->name, mod_name, mod_len) != 0)
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> libbpf.c:10070:21: note: 'mod_len' was declared here
> 10070 | int ret, i, mod_len;
> | ^~~~~~~
>
> Fixes: 8f8a024272f3 ("libbpf: support "module: Function" syntax for tracing programs")
> Signed-off-by: Achill Gilgenast <fossdd@pwned.life>
The code itself is actually okay. The error is triggered due to'maybe-uninitialized'.
To silence the compilation error, I think this change is okay.
Acked-by: Yonghong Song <yonghong.song@linux.dev>
> ---
> tools/lib/bpf/libbpf.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index e067cb5776bd..fb4d92c5c339 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -10086,27 +10086,27 @@ static int libbpf_find_prog_btf_id(const char *name, __u32 attach_prog_fd, int t
> btf__free(btf);
> if (err <= 0) {
> pr_warn("%s is not found in prog's BTF\n", name);
> goto out;
> }
> out:
> return err;
> }
>
> static int find_kernel_btf_id(struct bpf_object *obj, const char *attach_name,
> enum bpf_attach_type attach_type,
> int *btf_obj_fd, int *btf_type_id)
> {
> - int ret, i, mod_len;
> + int ret, i, mod_len = 0;
> const char *fn_name, *mod_name = NULL;
>
> fn_name = strchr(attach_name, ':');
> if (fn_name) {
> mod_name = attach_name;
> mod_len = fn_name - mod_name;
> fn_name++;
> }
>
> if (!mod_name || strncmp(mod_name, "vmlinux", mod_len) == 0) {
> ret = find_attach_btf_id(obj->btf_vmlinux,
> mod_name ? fn_name : attach_name,
> attach_type);
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] libbpf: avoid possible use of uninitialized mod_len
2025-07-29 16:17 ` Yonghong Song
@ 2025-07-30 16:13 ` Eduard Zingerman
2025-08-01 11:46 ` Achill Gilgenast
0 siblings, 1 reply; 6+ messages in thread
From: Eduard Zingerman @ 2025-07-30 16:13 UTC (permalink / raw)
To: Yonghong Song, Achill Gilgenast, Alexei Starovoitov,
Daniel Borkmann, Andrii Nakryiko, Viktor Malik, bpf
Cc: linux-kernel, Martin KaFai Lau, Song Liu, John Fastabend,
KP Singh, Stanislav Fomichev, Hao Luo, Jiri Olsa
On Tue, 2025-07-29 at 09:17 -0700, Yonghong Song wrote:
>
> On 7/29/25 2:45 AM, Achill Gilgenast wrote:
> > If not fn_name, mod_len does never get initialized which fails now with
> > gcc15 on Alpine Linux edge:
> >
> > libbpf.c: In function 'find_kernel_btf_id.constprop':
> > libbpf.c:10100:33: error: 'mod_len' may be used uninitialized [-Werror=maybe-uninitialized]
> > 10100 | if (mod_name && strncmp(mod->name, mod_name, mod_len) != 0)
> > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > libbpf.c:10070:21: note: 'mod_len' was declared here
> > 10070 | int ret, i, mod_len;
> > | ^~~~~~~
> >
> > Fixes: 8f8a024272f3 ("libbpf: support "module: Function" syntax for tracing programs")
> > Signed-off-by: Achill Gilgenast <fossdd@pwned.life>
>
> The code itself is actually okay. The error is triggered due to'maybe-uninitialized'.
> To silence the compilation error, I think this change is okay.
>
> Acked-by: Yonghong Song <yonghong.song@linux.dev>
I agree with Yonghong, `mod_len` is only read if mod_name != NULL,
meaning that "if (fn_name) { ... mod_name = ...; mod_len = ... }"
block was executed.
Please drop the "Fixes" tag.
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
[...]
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH] libbpf: avoid possible use of uninitialized mod_len
2025-07-30 16:13 ` Eduard Zingerman
@ 2025-08-01 11:46 ` Achill Gilgenast
2025-08-01 12:04 ` Achill Gilgenast
0 siblings, 1 reply; 6+ messages in thread
From: Achill Gilgenast @ 2025-08-01 11:46 UTC (permalink / raw)
To: Eduard Zingerman, Yonghong Song, Alexei Starovoitov,
Daniel Borkmann, Andrii Nakryiko, Viktor Malik, bpf
Cc: linux-kernel, Achill Gilgenast, Martin KaFai Lau, Song Liu,
John Fastabend, KP Singh, Stanislav Fomichev, Hao Luo, Jiri Olsa
If not fn_name, mod_len does never get initialized which fails now with
gcc15 on Alpine Linux edge:
libbpf.c: In function 'find_kernel_btf_id.constprop':
libbpf.c:10100:33: error: 'mod_len' may be used uninitialized [-Werror=maybe-uninitialized]
10100 | if (mod_name && strncmp(mod->name, mod_name, mod_len) != 0)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
libbpf.c:10070:21: note: 'mod_len' was declared here
10070 | int ret, i, mod_len;
| ^~~~~~~
Signed-off-by: Achill Gilgenast <fossdd@pwned.life>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/20250729094611.2065713-1-fossdd@pwned.life/
---
tools/lib/bpf/libbpf.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index e067cb5776bd..fb4d92c5c339 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -10086,27 +10086,27 @@ static int libbpf_find_prog_btf_id(const char *name, __u32 attach_prog_fd, int t
btf__free(btf);
if (err <= 0) {
pr_warn("%s is not found in prog's BTF\n", name);
goto out;
}
out:
return err;
}
static int find_kernel_btf_id(struct bpf_object *obj, const char *attach_name,
enum bpf_attach_type attach_type,
int *btf_obj_fd, int *btf_type_id)
{
- int ret, i, mod_len;
+ int ret, i, mod_len = 0;
const char *fn_name, *mod_name = NULL;
fn_name = strchr(attach_name, ':');
if (fn_name) {
mod_name = attach_name;
mod_len = fn_name - mod_name;
fn_name++;
}
if (!mod_name || strncmp(mod_name, "vmlinux", mod_len) == 0) {
ret = find_attach_btf_id(obj->btf_vmlinux,
mod_name ? fn_name : attach_name,
attach_type);
--
2.50.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] libbpf: avoid possible use of uninitialized mod_len
2025-08-01 11:46 ` Achill Gilgenast
@ 2025-08-01 12:04 ` Achill Gilgenast
2025-08-01 15:16 ` Alexei Starovoitov
0 siblings, 1 reply; 6+ messages in thread
From: Achill Gilgenast @ 2025-08-01 12:04 UTC (permalink / raw)
To: Eduard Zingerman, Yonghong Song, Alexei Starovoitov,
Daniel Borkmann, Andrii Nakryiko, Viktor Malik, bpf
Cc: linux-kernel, Martin KaFai Lau, Song Liu, John Fastabend,
KP Singh, Stanislav Fomichev, Hao Luo, Jiri Olsa,
Achill Gilgenast
On Fri Aug 1, 2025 at 1:46 PM CEST, Achill Gilgenast wrote:
> If not fn_name, mod_len does never get initialized which fails now with
> gcc15 on Alpine Linux edge:
>
> libbpf.c: In function 'find_kernel_btf_id.constprop':
> libbpf.c:10100:33: error: 'mod_len' may be used uninitialized [-Werror=maybe-uninitialized]
> 10100 | if (mod_name && strncmp(mod->name, mod_name, mod_len) != 0)
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> libbpf.c:10070:21: note: 'mod_len' was declared here
> 10070 | int ret, i, mod_len;
> | ^~~~~~~
>
> Signed-off-by: Achill Gilgenast <fossdd@pwned.life>
> Acked-by: Yonghong Song <yonghong.song@linux.dev>
> Acked-by: Eduard Zingerman <eddyz87@gmail.com>
> Link: https://lore.kernel.org/bpf/20250729094611.2065713-1-fossdd@pwned.life/
Oops, the subject should've been v2. I forgot to pass -v2 to git
send-email.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] libbpf: avoid possible use of uninitialized mod_len
2025-08-01 12:04 ` Achill Gilgenast
@ 2025-08-01 15:16 ` Alexei Starovoitov
0 siblings, 0 replies; 6+ messages in thread
From: Alexei Starovoitov @ 2025-08-01 15:16 UTC (permalink / raw)
To: Achill Gilgenast
Cc: Eduard Zingerman, Yonghong Song, Alexei Starovoitov,
Daniel Borkmann, Andrii Nakryiko, Viktor Malik, bpf, LKML,
Martin KaFai Lau, Song Liu, John Fastabend, KP Singh,
Stanislav Fomichev, Hao Luo, Jiri Olsa
On Fri, Aug 1, 2025 at 5:05 AM Achill Gilgenast <fossdd@pwned.life> wrote:
>
> On Fri Aug 1, 2025 at 1:46 PM CEST, Achill Gilgenast wrote:
> > If not fn_name, mod_len does never get initialized which fails now with
> > gcc15 on Alpine Linux edge:
> >
> > libbpf.c: In function 'find_kernel_btf_id.constprop':
> > libbpf.c:10100:33: error: 'mod_len' may be used uninitialized [-Werror=maybe-uninitialized]
> > 10100 | if (mod_name && strncmp(mod->name, mod_name, mod_len) != 0)
> > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > libbpf.c:10070:21: note: 'mod_len' was declared here
> > 10070 | int ret, i, mod_len;
> > | ^~~~~~~
> >
> > Signed-off-by: Achill Gilgenast <fossdd@pwned.life>
> > Acked-by: Yonghong Song <yonghong.song@linux.dev>
> > Acked-by: Eduard Zingerman <eddyz87@gmail.com>
> > Link: https://lore.kernel.org/bpf/20250729094611.2065713-1-fossdd@pwned.life/
>
> Oops, the subject should've been v2. I forgot to pass -v2 to git
> send-email.
No. It was already applied.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2025-08-01 15:17 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
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2025-07-29 9:45 [PATCH] libbpf: avoid possible use of uninitialized mod_len Achill Gilgenast
2025-07-29 16:17 ` Yonghong Song
2025-07-30 16:13 ` Eduard Zingerman
2025-08-01 11:46 ` Achill Gilgenast
2025-08-01 12:04 ` Achill Gilgenast
2025-08-01 15:16 ` Alexei Starovoitov
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