From ba1ebf3aef04922bfbe549bb5254765379d62f77 Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Fri, 20 Mar 2020 10:48:13 +0100 Subject: [PATCH] bpf: Explicitly memset the bpf_attr structure MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Reported-by: John Stultz Reported-by: Alexander Potapenko Reported-by: Alistair Delva Signed-off-by: Greg Kroah-Hartman Signed-off-by: Daniel Borkmann Acked-by: Yonghong Song 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 --- kernel/bpf/syscall.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index f5c1d5479ba3..8081e233a564 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -1474,7 +1474,7 @@ static int bpf_obj_get_info_by_fd(const union bpf_attr *attr, 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_attr __user *, uattr, unsigned int, siz 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; -- 2.20.1