* [PATCH v1 bpf-next] bpf: fix uninitialized values in BPF_{CORE,PROBE}_READ
@ 2025-04-29 13:08 Anton Protopopov
2025-04-29 14:21 ` Anton Protopopov
0 siblings, 1 reply; 2+ messages in thread
From: Anton Protopopov @ 2025-04-29 13:08 UTC (permalink / raw)
To: bpf; +Cc: Anton Protopopov
With the latest LLVM bpf selftests build will fail:
progs/profiler.inc.h:710:31: error: default initialization of an object of type 'typeof ((parent_task)->real_cred->uid.val)' (aka 'const unsigned int') leaves the object uninitialized and is incompatible with C++ [-Werror,-Wdefault-const-init-unsafe]
710 | proc_exec_data->parent_uid = BPF_CORE_READ(parent_task, real_cred, uid.val);
| ^
tools/testing/selftests/bpf/tools/include/bpf/bpf_core_read.h:520:35: note: expanded from macro 'BPF_CORE_READ'
520 | ___type((src), a, ##__VA_ARGS__) __r; \
| ^
Fix this by declaring __r to be an array of __u8 of a proper size.
Fixes: 792001f4f7aa ("libbpf: Add user-space variants of BPF_CORE_READ() family of macros")
Fixes: a4b09a9ef945 ("libbpf: Add non-CO-RE variants of BPF_CORE_READ() macro family")
Signed-off-by: Anton Protopopov <a.s.protopopov@gmail.com>
---
tools/lib/bpf/bpf_core_read.h | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)
diff --git a/tools/lib/bpf/bpf_core_read.h b/tools/lib/bpf/bpf_core_read.h
index c0e13cdf9660..be556ccdc002 100644
--- a/tools/lib/bpf/bpf_core_read.h
+++ b/tools/lib/bpf/bpf_core_read.h
@@ -517,9 +517,9 @@ extern void *bpf_rdonly_cast(const void *obj, __u32 btf_id) __ksym __weak;
* than enough for any practical purpose.
*/
#define BPF_CORE_READ(src, a, ...) ({ \
- ___type((src), a, ##__VA_ARGS__) __r; \
- BPF_CORE_READ_INTO(&__r, (src), a, ##__VA_ARGS__); \
- __r; \
+ __u8 __r[sizeof(___type((src), a, ##__VA_ARGS__))]; \
+ BPF_CORE_READ_INTO(__r, (src), a, ##__VA_ARGS__); \
+ *(___type((src), a, ##__VA_ARGS__) *)__r; \
})
/*
@@ -533,16 +533,16 @@ extern void *bpf_rdonly_cast(const void *obj, __u32 btf_id) __ksym __weak;
* input argument.
*/
#define BPF_CORE_READ_USER(src, a, ...) ({ \
- ___type((src), a, ##__VA_ARGS__) __r; \
- BPF_CORE_READ_USER_INTO(&__r, (src), a, ##__VA_ARGS__); \
- __r; \
+ __u8 __r[sizeof(___type((src), a, ##__VA_ARGS__))]; \
+ BPF_CORE_READ_USER_INTO(__r, (src), a, ##__VA_ARGS__); \
+ *(___type((src), a, ##__VA_ARGS__) *)__r; \
})
/* Non-CO-RE variant of BPF_CORE_READ() */
#define BPF_PROBE_READ(src, a, ...) ({ \
- ___type((src), a, ##__VA_ARGS__) __r; \
- BPF_PROBE_READ_INTO(&__r, (src), a, ##__VA_ARGS__); \
- __r; \
+ __u8 __r[sizeof(___type((src), a, ##__VA_ARGS__))]; \
+ BPF_PROBE_READ_INTO(__r, (src), a, ##__VA_ARGS__); \
+ *(___type((src), a, ##__VA_ARGS__) *)__r; \
})
/*
@@ -552,9 +552,9 @@ extern void *bpf_rdonly_cast(const void *obj, __u32 btf_id) __ksym __weak;
* not restricted to kernel types only.
*/
#define BPF_PROBE_READ_USER(src, a, ...) ({ \
- ___type((src), a, ##__VA_ARGS__) __r; \
- BPF_PROBE_READ_USER_INTO(&__r, (src), a, ##__VA_ARGS__); \
- __r; \
+ __u8 __r[sizeof(___type((src), a, ##__VA_ARGS__))]; \
+ BPF_PROBE_READ_USER_INTO(__r, (src), a, ##__VA_ARGS__); \
+ *(___type((src), a, ##__VA_ARGS__) *)__r; \
})
#endif
--
2.34.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v1 bpf-next] bpf: fix uninitialized values in BPF_{CORE,PROBE}_READ
2025-04-29 13:08 [PATCH v1 bpf-next] bpf: fix uninitialized values in BPF_{CORE,PROBE}_READ Anton Protopopov
@ 2025-04-29 14:21 ` Anton Protopopov
0 siblings, 0 replies; 2+ messages in thread
From: Anton Protopopov @ 2025-04-29 14:21 UTC (permalink / raw)
To: bpf
On 25/04/29 01:08PM, Anton Protopopov wrote:
> With the latest LLVM bpf selftests build will fail:
>
> progs/profiler.inc.h:710:31: error: default initialization of an object of type 'typeof ((parent_task)->real_cred->uid.val)' (aka 'const unsigned int') leaves the object uninitialized and is incompatible with C++ [-Werror,-Wdefault-const-init-unsafe]
> 710 | proc_exec_data->parent_uid = BPF_CORE_READ(parent_task, real_cred, uid.val);
> | ^
> tools/testing/selftests/bpf/tools/include/bpf/bpf_core_read.h:520:35: note: expanded from macro 'BPF_CORE_READ'
> 520 | ___type((src), a, ##__VA_ARGS__) __r; \
> | ^
>
> Fix this by declaring __r to be an array of __u8 of a proper size.
>
> Fixes: 792001f4f7aa ("libbpf: Add user-space variants of BPF_CORE_READ() family of macros")
> Fixes: a4b09a9ef945 ("libbpf: Add non-CO-RE variants of BPF_CORE_READ() macro family")
> Signed-off-by: Anton Protopopov <a.s.protopopov@gmail.com>
> ---
> tools/lib/bpf/bpf_core_read.h | 24 ++++++++++++------------
> 1 file changed, 12 insertions(+), 12 deletions(-)
>
> diff --git a/tools/lib/bpf/bpf_core_read.h b/tools/lib/bpf/bpf_core_read.h
> index c0e13cdf9660..be556ccdc002 100644
> --- a/tools/lib/bpf/bpf_core_read.h
> +++ b/tools/lib/bpf/bpf_core_read.h
> @@ -517,9 +517,9 @@ extern void *bpf_rdonly_cast(const void *obj, __u32 btf_id) __ksym __weak;
> * than enough for any practical purpose.
> */
> #define BPF_CORE_READ(src, a, ...) ({ \
> - ___type((src), a, ##__VA_ARGS__) __r; \
> - BPF_CORE_READ_INTO(&__r, (src), a, ##__VA_ARGS__); \
> - __r; \
> + __u8 __r[sizeof(___type((src), a, ##__VA_ARGS__))]; \
> + BPF_CORE_READ_INTO(__r, (src), a, ##__VA_ARGS__); \
And, of course, this breaks things. The line above should have stayed
with &. I will send v2.
> + *(___type((src), a, ##__VA_ARGS__) *)__r; \
> })
>
> /*
> @@ -533,16 +533,16 @@ extern void *bpf_rdonly_cast(const void *obj, __u32 btf_id) __ksym __weak;
> * input argument.
> */
> #define BPF_CORE_READ_USER(src, a, ...) ({ \
> - ___type((src), a, ##__VA_ARGS__) __r; \
> - BPF_CORE_READ_USER_INTO(&__r, (src), a, ##__VA_ARGS__); \
> - __r; \
> + __u8 __r[sizeof(___type((src), a, ##__VA_ARGS__))]; \
> + BPF_CORE_READ_USER_INTO(__r, (src), a, ##__VA_ARGS__); \
> + *(___type((src), a, ##__VA_ARGS__) *)__r; \
> })
>
> /* Non-CO-RE variant of BPF_CORE_READ() */
> #define BPF_PROBE_READ(src, a, ...) ({ \
> - ___type((src), a, ##__VA_ARGS__) __r; \
> - BPF_PROBE_READ_INTO(&__r, (src), a, ##__VA_ARGS__); \
> - __r; \
> + __u8 __r[sizeof(___type((src), a, ##__VA_ARGS__))]; \
> + BPF_PROBE_READ_INTO(__r, (src), a, ##__VA_ARGS__); \
> + *(___type((src), a, ##__VA_ARGS__) *)__r; \
> })
>
> /*
> @@ -552,9 +552,9 @@ extern void *bpf_rdonly_cast(const void *obj, __u32 btf_id) __ksym __weak;
> * not restricted to kernel types only.
> */
> #define BPF_PROBE_READ_USER(src, a, ...) ({ \
> - ___type((src), a, ##__VA_ARGS__) __r; \
> - BPF_PROBE_READ_USER_INTO(&__r, (src), a, ##__VA_ARGS__); \
> - __r; \
> + __u8 __r[sizeof(___type((src), a, ##__VA_ARGS__))]; \
> + BPF_PROBE_READ_USER_INTO(__r, (src), a, ##__VA_ARGS__); \
> + *(___type((src), a, ##__VA_ARGS__) *)__r; \
> })
>
> #endif
> --
> 2.34.1
>
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2025-04-29 14:16 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2025-04-29 13:08 [PATCH v1 bpf-next] bpf: fix uninitialized values in BPF_{CORE,PROBE}_READ Anton Protopopov
2025-04-29 14:21 ` Anton Protopopov
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox