From: Greg Kroah-Hartman gregkh@linuxfoundation.org
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@google.com Reported-by: John Stultz john.stultz@linaro.org Reported-by: Alexander Potapenko glider@google.com Reported-by: Alistair Delva adelva@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Daniel Borkmann daniel@iogearbox.net Acked-by: Yonghong Song yhs@fb.com Link: https://android-review.googlesource.com/c/kernel/common/+/1235490 Link: https://lore.kernel.org/bpf/20200320094813.GA421650@kroah.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/bpf/syscall.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -1474,7 +1474,7 @@ static int bpf_obj_get_info_by_fd(const
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)) @@ -1486,6 +1486,7 @@ 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;