Subject: [PATCH] bpf: explicitly memset some bpf info structures declared on the stack

From: Greg Kroah-Hartman <[email-masked]>
Date: Fri, 20 Mar 2020 17:22:58 +0100

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 <[email-masked]
Signed-off-by: Greg Kroah-Hartman <[email-masked]>
---

Note, this is separate from my previous patch, both are needed.

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

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 787140095e58..2fc945fcf952 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -4564,7 +4564,7 @@ int btf_get_info_by_fd(const struct btf *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;
@@ -4573,6 +4573,7 @@ int btf_get_info_by_fd(const struct btf *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;
 
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index a4b1de8ea409..84213cc5d016 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2787,7 +2787,7 @@ static int bpf_prog_get_info_by_fd(struct bpf_prog *prog,
 				   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;
@@ -2799,6 +2799,7 @@ static int bpf_prog_get_info_by_fd(struct bpf_prog *prog,
 		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;
 
@@ -3062,7 +3063,7 @@ static int bpf_map_get_info_by_fd(struct bpf_map *map,
 				  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;
 
@@ -3071,6 +3072,7 @@ static int bpf_map_get_info_by_fd(struct bpf_map *map,
 		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;
-- 
2.25.2