From: Brendan Jackman <jackmanb@google.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: bpf <bpf@vger.kernel.org>, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
open list <linux-kernel@vger.kernel.org>,
KP Singh <kpsingh@kernel.org>,
Florent Revest <revest@chromium.org>
Subject: Re: [PATCH v2 bpf-next] libbpf: Fix signed overflow in ringbuf_process_ring
Date: Tue, 4 May 2021 11:01:33 +0200 [thread overview]
Message-ID: <CA+i-1C1V4b3LvB+pwDn5zomGG1ehSppX=r6TMfPutbgaoG_53Q@mail.gmail.com> (raw)
In-Reply-To: <CAEf4BzY1bftPAj_hjE4SBVv2P1U7twW3FdRsvNP9kPCMe_NOjA@mail.gmail.com>
On Mon, 3 May 2021 at 19:46, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
>
> On Mon, May 3, 2021 at 5:01 AM Brendan Jackman <jackmanb@google.com> wrote:
> >
> > On Fri, 30 Apr 2021 at 18:31, Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:
> So while doing that I noticed that you didn't fix ring_buffer__poll(),
> so I had to fix it up a bit more extensively. Please check the end
> result in bpf tree and let me know if there are any problems with it:
>
> 2a30f9440640 ("libbpf: Fix signed overflow in ringbuf_process_ring")
Ah, thanks for that. Yep, the additional fix looks good to me.
I think it actually fixes another very niche issue:
int ring_buffer__poll(struct ring_buffer *rb, int timeout_ms)
{
- int i, cnt, err, res = 0;
+ int i, cnt;
+ int64_t err, res = 0;
cnt = epoll_wait(rb->epoll_fd, rb->events, rb->ring_cnt, timeout_ms);
+ if (cnt < 0)
+ return -errno;
+
for (i = 0; i < cnt; i++) {
__u32 ring_id = rb->events[i].data.fd;
struct ring *ring = &rb->rings[ring_id];
@@ -280,7 +290,9 @@ int ring_buffer__poll(struct ring_buffer *rb, int
timeout_ms)
return err;
res += err;
}
- return cnt < 0 ? -errno : res;
If the callback returns an error but errno is 0 this fails to report the error.
errno(3) says "the value of errno is never set to zero by any system
call or library function" but then describes a scenario where an
application might usefully set it to zero itself. Maybe it can also be
0 in new threads, depending on your metaphysical interpretation of "by
a system call or library function".
+ if (res > INT_MAX)
+ return INT_MAX;
+ return res;
next prev parent reply other threads:[~2021-05-04 9:01 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-29 13:05 [PATCH v2 bpf-next] libbpf: Fix signed overflow in ringbuf_process_ring Brendan Jackman
2021-04-30 16:31 ` Andrii Nakryiko
2021-05-03 12:01 ` Brendan Jackman
2021-05-03 17:46 ` Andrii Nakryiko
2021-05-04 9:01 ` Brendan Jackman [this message]
2021-05-05 0:37 ` Andrii Nakryiko
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