[PATCH 5.5 13/30] bpf: Explicitly memset some bpf info structures declared on the stack

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

commit 5c6f25887963f15492b604dd25cb149c501bbabf upstream.

Trying to initialize a structure with "= {};" will not always clean out
all padding locations in a structure. So be explicit and call memset to
initialize everything for a number of bpf information structures that
are then copied from userspace, sometimes from smaller memory locations
than the size of the structure.

Reported-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Acked-by: Yonghong Song <yhs@xxxxxx>
Link: https://lore.kernel.org/bpf/20200320162258.GA794295@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 kernel/bpf/btf.c     |    3 ++-
 kernel/bpf/syscall.c |    6 ++++--
 2 files changed, 6 insertions(+), 3 deletions(-)

--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -4218,7 +4218,7 @@ int btf_get_info_by_fd(const struct btf
 		       union bpf_attr __user *uattr)
 {
 	struct bpf_btf_info __user *uinfo;
-	struct bpf_btf_info info = {};
+	struct bpf_btf_info info;
 	u32 info_copy, btf_copy;
 	void __user *ubtf;
 	u32 uinfo_len;
@@ -4227,6 +4227,7 @@ int btf_get_info_by_fd(const struct btf
 	uinfo_len = attr->info.info_len;
 
 	info_copy = min_t(u32, uinfo_len, sizeof(info));
+	memset(&info, 0, sizeof(info));
 	if (copy_from_user(&info, uinfo, info_copy))
 		return -EFAULT;
 
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2477,7 +2477,7 @@ static int bpf_prog_get_info_by_fd(struc
 				   union bpf_attr __user *uattr)
 {
 	struct bpf_prog_info __user *uinfo = u64_to_user_ptr(attr->info.info);
-	struct bpf_prog_info info = {};
+	struct bpf_prog_info info;
 	u32 info_len = attr->info.info_len;
 	struct bpf_prog_stats stats;
 	char __user *uinsns;
@@ -2489,6 +2489,7 @@ static int bpf_prog_get_info_by_fd(struc
 		return err;
 	info_len = min_t(u32, sizeof(info), info_len);
 
+	memset(&info, 0, sizeof(info));
 	if (copy_from_user(&info, uinfo, info_len))
 		return -EFAULT;
 
@@ -2752,7 +2753,7 @@ static int bpf_map_get_info_by_fd(struct
 				  union bpf_attr __user *uattr)
 {
 	struct bpf_map_info __user *uinfo = u64_to_user_ptr(attr->info.info);
-	struct bpf_map_info info = {};
+	struct bpf_map_info info;
 	u32 info_len = attr->info.info_len;
 	int err;
 
@@ -2761,6 +2762,7 @@ static int bpf_map_get_info_by_fd(struct
 		return err;
 	info_len = min_t(u32, sizeof(info), info_len);
 
+	memset(&info, 0, sizeof(info));
 	info.type = map->map_type;
 	info.id = map->id;
 	info.key_size = map->key_size;