From: Greg Kroah-Hartman Date: Fri, 20 Mar 2020 09:48:13 +0000 (+0100) Subject: bpf: Explicitly memset the bpf_attr structure X-Git-Tag: v5.6~4^2^2~1 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8096f229421f7b22433775e928d506f0342e5907;p=thirdparty%2Flinux.git bpf: Explicitly memset the bpf_attr structure 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 --- diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 2857b7dda382c..3ac1629cf00e2 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -3362,7 +3362,7 @@ err_put: 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)) @@ -3374,6 +3374,7 @@ 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;