From: Yonghong Song <yhs@fb.com>
To: Daniel Borkmann <daniel@iogearbox.net>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Alexei Starovoitov <ast@kernel.org>
Cc: "Martin KaFai Lau" <kafai@fb.com>,
"Song Liu" <songliubraving@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 08:31:03 -0700 [thread overview]
Message-ID: <7bf271b1-4909-d12d-bc65-d18790f7683e@fb.com> (raw)
In-Reply-To: <3bcf52da-0930-a27f-60f9-28a40e639949@iogearbox.net>
On 3/20/20 8:24 AM, Daniel Borkmann wrote:
> 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://urldefense.proofpoint.com/v2/url?u=https-3A__android-2Dreview.googlesource.com_c_kernel_common_-2B_1235490&d=DwIDaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=DA8e1B5r073vIqRrFz7MRA&m=Fz_Xc6psG64uMowK2qpH0gTLj0NQE7k1CTWb5fODVeg&s=WKW0vq8WBALfwsSq5xGGWwxuLWKfI0DNN9XVMc1DkcE&e=
>> 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()
Not sure whether in these places existing approach will cause
kernel failure or not. They did not call CHECK_ATTR, e.g.,
for bpf_prog_info structure.
>
> 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 15:31 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
2020-03-20 15:31 ` Yonghong Song [this message]
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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