[PATCH 5.4 12/27] bpf: Explicitly memset some bpf info structures declared on the stack

From: Greg Kroah-Hartman
Date: Wed Apr 01 2020 - 12:21:48 EST


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
@@ -3460,7 +3460,7 @@ 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;
@@ -3469,6 +3469,7 @@ 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
@@ -2325,7 +2325,7 @@ 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;
@@ -2337,6 +2337,7 @@ 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;

@@ -2600,7 +2601,7 @@ 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;

@@ -2609,6 +2610,7 @@ 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;