The log buffer of common attributes would be confusing with the one in
'union bpf_attr' for BPF_PROG_LOAD.
In order to clarify the usage of these two log buffers, they both can be
used for logging if:
* They are same, including 'log_buf', 'log_level' and 'log_size'.
* One of them is missing, then another one will be used for logging.
If they both have 'log_buf' but they are not same totally, return -EINVAL.
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
include/linux/bpf_verifier.h | 4 +++-
kernel/bpf/log.c | 29 ++++++++++++++++++++++++++---
kernel/bpf/syscall.c | 9 ++++++---
3 files changed, 35 insertions(+), 7 deletions(-)
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 4a0c5ef296b9..7eb024e83d2d 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -637,9 +637,11 @@ struct bpf_log_attr {
u32 log_level;
struct bpf_attrs *attrs;
u32 offsetof_log_true_size;
+ struct bpf_attrs *attrs_common;
};
-int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs);
+int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs,
+ struct bpf_attrs *attrs_common);
int bpf_log_attr_finalize(struct bpf_log_attr *log_attr, struct bpf_verifier_log *log);
#define BPF_MAX_SUBPROGS 256
diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c
index 457b724c4176..c0b816e84384 100644
--- a/kernel/bpf/log.c
+++ b/kernel/bpf/log.c
@@ -865,23 +865,41 @@ void print_insn_state(struct bpf_verifier_env *env, const struct bpf_verifier_st
}
static int bpf_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs, u64 log_buf,
- u32 log_size, u32 log_level, int offsetof_log_true_size)
+ u32 log_size, u32 log_level, int offsetof_log_true_size,
+ struct bpf_attrs *attrs_common)
{
+ const struct bpf_common_attr *common = attrs_common ? attrs_common->attr : NULL;
+
memset(log_attr, 0, sizeof(*log_attr));
log_attr->log_buf = log_buf;
log_attr->log_size = log_size;
log_attr->log_level = log_level;
log_attr->attrs = attrs;
log_attr->offsetof_log_true_size = offsetof_log_true_size;
+ log_attr->attrs_common = attrs_common;
+
+ if (log_buf && common && common->log_buf &&
+ (log_buf != common->log_buf ||
+ log_size != common->log_size ||
+ log_level != common->log_level))
+ return -EINVAL;
+
+ if (!log_buf && common && common->log_buf) {
+ log_attr->log_buf = common->log_buf;
+ log_attr->log_size = common->log_size;
+ log_attr->log_level = common->log_level;
+ }
+
return 0;
}
-int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs)
+int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs,
+ struct bpf_attrs *attrs_common)
{
const union bpf_attr *attr = attrs->attr;
return bpf_log_attr_init(log_attr, attrs, attr->log_buf, attr->log_size, attr->log_level,
- offsetof(union bpf_attr, log_true_size));
+ offsetof(union bpf_attr, log_true_size), attrs_common);
}
int bpf_log_attr_finalize(struct bpf_log_attr *log_attr, struct bpf_verifier_log *log)
@@ -901,5 +919,10 @@ int bpf_log_attr_finalize(struct bpf_log_attr *log_attr, struct bpf_verifier_log
copy_to_bpfptr_offset(log_attr->attrs->uattr, off, &log_true_size, size))
err = -EFAULT;
+ off = offsetof(struct bpf_common_attr, log_true_size);
+ if (log_attr->attrs_common && log_attr->attrs_common->size >= off + size &&
+ copy_to_bpfptr_offset(log_attr->attrs_common->uattr, off, &log_true_size, size))
+ err = -EFAULT;
+
return err;
}
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index d422664e00dd..3d1d1181b9b4 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2865,7 +2865,8 @@ static int bpf_prog_mark_insn_arrays_ready(struct bpf_prog *prog)
/* last field in 'union bpf_attr' used by this command */
#define BPF_PROG_LOAD_LAST_FIELD keyring_id
-static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
+static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size,
+ struct bpf_attrs *attrs_common)
{
enum bpf_prog_type type = attr->prog_type;
struct bpf_prog *prog, *dst_prog = NULL;
@@ -3085,7 +3086,7 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
goto free_prog_sec;
bpf_attrs_init(&attrs, attr, uattr, uattr_size);
- err = bpf_prog_load_log_attr_init(&log_attr, &attrs);
+ err = bpf_prog_load_log_attr_init(&log_attr, &attrs, attrs_common);
if (err < 0)
goto free_used_maps;
@@ -6190,6 +6191,7 @@ static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size,
bpfptr_t uattr_common, unsigned int size_common)
{
struct bpf_common_attr attr_common;
+ struct bpf_attrs attrs_common;
union bpf_attr attr;
int err;
@@ -6241,7 +6243,8 @@ static int __sys_bpf(enum bpf_cmd cmd, bpfptr_t uattr, unsigned int size,
err = map_freeze(&attr);
break;
case BPF_PROG_LOAD:
- err = bpf_prog_load(&attr, uattr, size);
+ bpf_attrs_init(&attrs_common, &attr_common, uattr_common, size_common);
+ err = bpf_prog_load(&attr, uattr, size, &attrs_common);
break;
case BPF_OBJ_PIN:
err = bpf_obj_pin(&attr);
--
2.52.0,
On Mon, Jan 26, 2026 at 7:15 AM Leon Hwang <leon.hwang@linux.dev> wrote:
>
> The log buffer of common attributes would be confusing with the one in
> 'union bpf_attr' for BPF_PROG_LOAD.
>
> In order to clarify the usage of these two log buffers, they both can be
> used for logging if:
>
> * They are same, including 'log_buf', 'log_level' and 'log_size'.
> * One of them is missing, then another one will be used for logging.
>
> If they both have 'log_buf' but they are not same totally, return -EINVAL.
>
> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
> ---
> include/linux/bpf_verifier.h | 4 +++-
> kernel/bpf/log.c | 29 ++++++++++++++++++++++++++---
> kernel/bpf/syscall.c | 9 ++++++---
> 3 files changed, 35 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
> index 4a0c5ef296b9..7eb024e83d2d 100644
> --- a/include/linux/bpf_verifier.h
> +++ b/include/linux/bpf_verifier.h
> @@ -637,9 +637,11 @@ struct bpf_log_attr {
> u32 log_level;
> struct bpf_attrs *attrs;
> u32 offsetof_log_true_size;
> + struct bpf_attrs *attrs_common;
> };
>
> -int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs);
> +int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs,
> + struct bpf_attrs *attrs_common);
> int bpf_log_attr_finalize(struct bpf_log_attr *log_attr, struct bpf_verifier_log *log);
>
> #define BPF_MAX_SUBPROGS 256
> diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c
> index 457b724c4176..c0b816e84384 100644
> --- a/kernel/bpf/log.c
> +++ b/kernel/bpf/log.c
> @@ -865,23 +865,41 @@ void print_insn_state(struct bpf_verifier_env *env, const struct bpf_verifier_st
> }
>
> static int bpf_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs, u64 log_buf,
> - u32 log_size, u32 log_level, int offsetof_log_true_size)
> + u32 log_size, u32 log_level, int offsetof_log_true_size,
> + struct bpf_attrs *attrs_common)
> {
> + const struct bpf_common_attr *common = attrs_common ? attrs_common->attr : NULL;
> +
It seems the only point of struct bpf_attrs is to pass the attrs
here and remember them in bpf_log_attr.
It looks unnecessary. Also the cast to void and back to actual
type doesn't look pretty.
It seems all of it is to do two copy_to_bpfptr_offset() of log_true_size
in different places,
but libbpf will use only one, so let's do only one
copy_to_bpfptr_offset() and simply the whole thing.
struct bpf_log_attr only needs
u32 offsetof_true_size;
bpfptr_t uattr;
No need to introduce bpf_attrs and bpf_attrs_init() either.
When bpf_log_attr is inited make the choice of uattr and offset.
uattr will point at either new bpf_common_attr or old bpf_attr,
and offsetof_true_size will have 3 possible offsets.
pw-bot: cr
On 2026/1/27 10:43, Alexei Starovoitov wrote:
> ,
>
>
> On Mon, Jan 26, 2026 at 7:15 AM Leon Hwang <leon.hwang@linux.dev> wrote:
>>
>> The log buffer of common attributes would be confusing with the one in
>> 'union bpf_attr' for BPF_PROG_LOAD.
>>
>> In order to clarify the usage of these two log buffers, they both can be
>> used for logging if:
>>
>> * They are same, including 'log_buf', 'log_level' and 'log_size'.
>> * One of them is missing, then another one will be used for logging.
>>
>> If they both have 'log_buf' but they are not same totally, return -EINVAL.
>>
>> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
>> ---
>> include/linux/bpf_verifier.h | 4 +++-
>> kernel/bpf/log.c | 29 ++++++++++++++++++++++++++---
>> kernel/bpf/syscall.c | 9 ++++++---
>> 3 files changed, 35 insertions(+), 7 deletions(-)
>>
>> diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
>> index 4a0c5ef296b9..7eb024e83d2d 100644
>> --- a/include/linux/bpf_verifier.h
>> +++ b/include/linux/bpf_verifier.h
>> @@ -637,9 +637,11 @@ struct bpf_log_attr {
>> u32 log_level;
>> struct bpf_attrs *attrs;
>> u32 offsetof_log_true_size;
>> + struct bpf_attrs *attrs_common;
>> };
>>
>> -int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs);
>> +int bpf_prog_load_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs,
>> + struct bpf_attrs *attrs_common);
>> int bpf_log_attr_finalize(struct bpf_log_attr *log_attr, struct bpf_verifier_log *log);
>>
>> #define BPF_MAX_SUBPROGS 256
>> diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c
>> index 457b724c4176..c0b816e84384 100644
>> --- a/kernel/bpf/log.c
>> +++ b/kernel/bpf/log.c
>> @@ -865,23 +865,41 @@ void print_insn_state(struct bpf_verifier_env *env, const struct bpf_verifier_st
>> }
>>
>> static int bpf_log_attr_init(struct bpf_log_attr *log_attr, struct bpf_attrs *attrs, u64 log_buf,
>> - u32 log_size, u32 log_level, int offsetof_log_true_size)
>> + u32 log_size, u32 log_level, int offsetof_log_true_size,
>> + struct bpf_attrs *attrs_common)
>> {
>> + const struct bpf_common_attr *common = attrs_common ? attrs_common->attr : NULL;
>> +
>
> It seems the only point of struct bpf_attrs is to pass the attrs
> here and remember them in bpf_log_attr.
> It looks unnecessary. Also the cast to void and back to actual
> type doesn't look pretty.
> It seems all of it is to do two copy_to_bpfptr_offset() of log_true_size
> in different places,
> but libbpf will use only one, so let's do only one
> copy_to_bpfptr_offset() and simply the whole thing.
> struct bpf_log_attr only needs
> u32 offsetof_true_size;
> bpfptr_t uattr;
>
> No need to introduce bpf_attrs and bpf_attrs_init() either.
> When bpf_log_attr is inited make the choice of uattr and offset.
> uattr will point at either new bpf_common_attr or old bpf_attr,
> and offsetof_true_size will have 3 possible offsets.
>
That makes sense.
Then struct bpf_log_attr can be simplified to:
struct bpf_log_attr {
u32 offsetof_true_size;
u32 size;
bpfptr_t uattr;
};
And bpf_log_attr_finalize() would become:
int bpf_log_attr_finalize(struct bpf_log_attr *attr, struct
bpf_verifier_log *log)
{
...
err = bpf_vlog_finalize(log, &log_true_size);
size = sizeof(log_true_size);
if (attr->size >= off + size &&
copy_to_bpfptr_offset(attr->uattr, attr->offsetof_true_size,
&log_true_size, size))
err = -EFAULT;
return err;
}
Thanks,
Leon
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