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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 <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
This commit is contained in:
Greg Kroah-Hartman 2020-03-20 10:48:13 +01:00 committed by Daniel Borkmann
parent 8e7ae2518f
commit 8096f22942
1 changed files with 2 additions and 1 deletions
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3
kernel/bpf/syscall.c
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@ -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;