[PATCH bpf-next v6 4/9] bpf: Add syscall common attributes support for prog_load

[Leon Hwang <leon.hwang@linux.dev>]

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 4c9632c40059..da2d37ca60e7 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 645cc0c0cd3f..ea59cd178dcf 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;
 
@@ -6174,6 +6175,7 @@ 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;
 
@@ -6225,7 +6227,8 @@ 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