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Message-ID: <aca27db2-5c16-6bf8-e601-be8b42678cd4@iogearbox.net> Date: Wed, 1 May 2019 23:44:09 +0200 From: Daniel Borkmann <daniel@...earbox.net> To: Wang YanQing <udknight@...il.com>, ast@...nel.org, davem@...emloft.net, kuznet@....inr.ac.ru, tglx@...utronix.de, netdev@...r.kernel.org, bpf@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v2] bpf, x32: Fix bug for BPF_JMP | {BPF_JSGT, BPF_JSLE, BPF_JSLT, BPF_JSGE} On 04/27/2019 10:28 AM, Wang YanQing wrote: > 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 and adds a testcase in selftests/bpf for such bug. > > Signed-off-by: Wang YanQing <udknight@...il.com> Applied, thanks!
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