From: Daniel Borkmann <daniel@iogearbox.net>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Alexei Starovoitov <ast@kernel.org>
Cc: "Martin KaFai Lau" <kafai@fb.com>,
"Song Liu" <songliubraving@fb.com>, "Yonghong Song" <yhs@fb.com>,
"Andrii Nakryiko" <andriin@fb.com>,
netdev@vger.kernel.org, bpf@vger.kernel.org,
linux-kernel@vger.kernel.org,
"Maciej Żenczykowski" <maze@google.com>,
"John Stultz" <john.stultz@linaro.org>,
"Alexander Potapenko" <glider@google.com>,
"Alistair Delva" <adelva@google.com>
Subject: Re: [PATCH] bpf: explicitly memset the bpf_attr structure
Date: Fri, 20 Mar 2020 16:24:32 +0100 [thread overview]
Message-ID: <3bcf52da-0930-a27f-60f9-28a40e639949@iogearbox.net> (raw)
In-Reply-To: <20200320094813.GA421650@kroah.com>
On 3/20/20 10:48 AM, Greg Kroah-Hartman wrote:
> 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>
> Cc: stable <stable@vger.kernel.org>
> Link: https://android-review.googlesource.com/c/kernel/common/+/1235490
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---
> 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 a91ad518c050..a4b1de8ea409 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -3354,7 +3354,7 @@ static int bpf_map_do_batch(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))
> @@ -3366,6 +3366,7 @@ 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));
Thanks for the fix, there are a few more of these places. We would also need
to cover:
- bpf_prog_get_info_by_fd()
- bpf_map_get_info_by_fd()
- btf_get_info_by_fd()
Please add these as well to your fix.
> if (copy_from_user(&attr, uattr, size) != 0)
> return -EFAULT;
>
>
> base-commit: 6c90b86a745a446717fdf408c4a8a4631a5e8ee3
>
next prev parent reply other threads:[~2020-03-20 15:24 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-20 9:48 [PATCH] bpf: explicitly memset the bpf_attr structure Greg Kroah-Hartman
2020-03-20 15:23 ` Yonghong Song
2020-03-20 15:46 ` Greg Kroah-Hartman
2020-03-20 15:24 ` Daniel Borkmann [this message]
2020-03-20 15:31 ` Yonghong Song
2020-03-20 15:45 ` Greg Kroah-Hartman
2020-03-20 16:04 ` Daniel Borkmann
2020-03-20 16:15 ` Greg Kroah-Hartman
2020-03-20 16:22 ` [PATCH] bpf: explicitly memset some bpf info structures declared on the stack Greg Kroah-Hartman
2020-03-20 18:34 ` Yonghong Song
2020-03-20 20:07 ` Daniel Borkmann
2020-03-20 20:07 ` [PATCH] bpf: explicitly memset the bpf_attr structure Daniel Borkmann
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