From: Greg KH <greg@kroah.com>
To: Daniel Borkmann <daniel@iogearbox.net>
Cc: Wang YanQing <udknight@gmail.com>,
stable@vger.kernel.org, stephen@networkplumber.org,
ast@kernel.org, songliubraving@fb.com, yhs@fb.com,
itugrok@yahoo.com, bpf@vger.kernel.org
Subject: Re: [PATCH] bpf, x32: Fix bug for BPF_JMP | {BPF_JSGT, BPF_JSLE, BPF_JSLT, BPF_JSGE}
Date: Thu, 21 Nov 2019 23:37:38 +0100 [thread overview]
Message-ID: <20191121223738.GA1170586@kroah.com> (raw)
In-Reply-To: <be634e7c-98f4-cd7d-6967-485dc0bd2ebc@iogearbox.net>
On Thu, Nov 21, 2019 at 10:43:28AM +0100, Daniel Borkmann wrote:
> On 11/21/19 8:43 AM, Wang YanQing wrote:
> > commit 711aef1bbf88212a21f7103e88f397b47a528805 upstream.
> >
> > The current method to compare 64-bit numbers for conditional jump is:
> >
> > 1) Compare the high 32-bit first.
> >
> > 2) If the high 32-bit isn't the same, then goto step 4.
> >
> > 3) Compare the low 32-bit.
> >
> > 4) Check the desired condition.
> >
> > This method is right for unsigned comparison, but it is buggy for signed
> > comparison, because it does signed comparison for low 32-bit too.
> >
> > There is only one sign bit in 64-bit number, that is the MSB in the 64-bit
> > number, it is wrong to treat low 32-bit as signed number and do the signed
> > comparison for it.
> >
> > This patch fixes the bug.
> >
> > Note:
> > The original commit adds a testcase in selftests/bpf for such bug, this
> > backport patch doesn't include the testcase, because the testcase needs
> > another upstream commit.
> >
> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=205469
> > Reported-by: Tony Ambardar <itugrok@yahoo.com>
> > Cc: Tony Ambardar <itugrok@yahoo.com>
> > Cc: stable@vger.kernel.org #v4.19
> > Signed-off-by: Wang YanQing <udknight@gmail.com>
> > Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
>
> Thanks a lot for backporting & testing, Wang, much appreciated! Greg, if you get a
> chance, please queue this & the other stable requests from Wang up.
All now queued up, thanks.
greg k-h
prev parent reply other threads:[~2019-11-21 22:37 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-21 7:43 [PATCH] bpf, x32: Fix bug for BPF_JMP | {BPF_JSGT, BPF_JSLE, BPF_JSLT, BPF_JSGE} Wang YanQing
2019-11-21 9:43 ` Daniel Borkmann
2019-11-21 22:37 ` Greg KH [this message]
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