From: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> commit 8096f229421f7b22433775e928d506f0342e5907 upstream. For the bpf syscall, we are relying on the compiler to properly zero out the bpf_attr union that we copy userspace data into. Unfortunately that doesn't always work properly, padding and other oddities might not be correctly zeroed, and in some tests odd things have been found when the stack is pre-initialized to other values. Fix this by explicitly memsetting the structure to 0 before using it. Reported-by: Maciej Żenczykowski <maze@xxxxxxxxxx> Reported-by: John Stultz <john.stultz@xxxxxxxxxx> Reported-by: Alexander Potapenko <glider@xxxxxxxxxx> Reported-by: Alistair Delva <adelva@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx> Acked-by: Yonghong Song <yhs@xxxxxx> Link: https://android-review.googlesource.com/c/kernel/common/+/1235490 Link: https://lore.kernel.org/bpf/20200320094813.GA421650@xxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- kernel/bpf/syscall.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -2988,7 +2988,7 @@ out: SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size) { - union bpf_attr attr = {}; + union bpf_attr attr; int err; if (sysctl_unprivileged_bpf_disabled && !capable(CAP_SYS_ADMIN)) @@ -3000,6 +3000,7 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf size = min_t(u32, size, sizeof(attr)); /* copy attributes from user space, may be less than sizeof(bpf_attr) */ + memset(&attr, 0, sizeof(attr)); if (copy_from_user(&attr, uattr, size) != 0) return -EFAULT;
