linux-kernel - Re: bpf selftest failed in 5.4.210 kernel

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Message-ID: <CAPXMrf8VsNMKNLxFjdytk57mk_9ZC0avg1qCGLSMOZNirpdboQ@mail.gmail.com>
Date:   Fri, 19 Aug 2022 19:20:11 +0300
From:   RAJESH DASARI <raajeshdasari@...il.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Jean-Philippe Brucker <jean-philippe@...aro.org>,
        stable@...r.kernel.org, linux-kernel@...r.kernel.org, df@...gle.com
Subject: Re: bpf selftest failed in 5.4.210 kernel

Hi ,

I did some more tests ,  Please find the observation below.

step 1:  On v5.4.210 kernel , I reverted  only commit  bpf: Verifer,
adjust_scalar_min_max_vals to always call update_reg_bounds()
7c1134c7da997523e2834dd516e2ddc51920699a , compiled the kernel and
booted the system with the new kernel.
step 2:  On system with newly compiled kernel , I clone the  v54.4.210
source code  and  reverted  commit  selftests/bpf: Fix test_align
verifier log patterns  and selftests/bpf: Fix "dubious pointer
arithmetic" test , then ran the selftests, test_align test cases
execution was successful.
step 3: If i revert only selftests/bpf: Fix "dubious pointer
arithmetic" test , test cases are still failing.



Please find the attached PDF for the other scenarios which I have executed.





Thanks,
Rajesh Dasari.

On Fri, Aug 19, 2022 at 1:57 PM Greg KH <gregkh@...uxfoundation.org> wrote:
>
> On Thu, Aug 18, 2022 at 08:55:16AM +0100, Jean-Philippe Brucker wrote:
> > On Thu, Aug 18, 2022 at 07:24:03AM +0200, Greg KH wrote:
> > > On Wed, Aug 17, 2022 at 09:22:00PM +0300, RAJESH DASARI wrote:
> > > > Hi ,
> > > >
> > > > We are running bpf selftests on 5.4.210 kernel version and we see that
> > > > test case 11 of  test_align failed. Please find the below error.
> > > >
> > > > selftests: bpf: test_align
> > > > Test  11: pointer variable subtraction ... Failed to find match 16:
> > > > R5_w=pkt(id=2,off=0,r=0,umin_value=2,umax_value=1082,var_off=(0x2;
> > > > 0xfffffffc)
> > > > # func#0 @0
> > > > # 0: R1=ctx(id=0,off=0,imm=0) R10=fp0
> > > > # 0: (61) r2 = *(u32 *)(r1 +76)
> > > > # 1: R1=ctx(id=0,off=0,imm=0) R2_w=pkt(id=0,off=0,r=0,imm=0) R10=fp0
> > > > # 1: (61) r3 = *(u32 *)(r1 +80)
> > > >
> > > > For complete errors please see the attached file. The same test case
> > > > execution was successful in the 5.4.209 version , could you please let
> > > > me know any known issue with the recent changes in 5.4.210 and how to
> > > > fix these errors.
> > >
> > > Can you use 'git bisect' to find the offending commit?
> >
> > It probably is 6098562ed9df ("selftests/bpf: Fix "dubious pointer
> > arithmetic" test")
> > https://lore.kernel.org/all/20220803145005.2385039-6-ovidiu.panait@windriver.com/
> > Could you try reverting that?
> >
> > The patch didn't have a Fixes: tags, because the bugfix it refers to was
> > merged at the same time. That bugfix is upstream commit b02709587ea3
> > ("bpf: Fix propagation of 32-bit signed bounds from 64-bit bounds.")
> >
> > Since b02709587ea3 was only backported down to 5.10, this fix shouldn't be
> > in 5.4. Sorry for not catching this earlier.
>
> Can you send in a revert for this?
>
> thanks,
>
> greg k-h

Download attachment "selftest-on-5.4.210.pdf" of type "application/pdf" (48577 bytes)