[PATCH v2] bpf: core: fix shift-out-of-bounds in ___bpf_prog_run

Greg KH gregkh at linuxfoundation.org
Wed Jun 2 06:09:48 UTC 2021


On Tue, Jun 01, 2021 at 11:28:00PM +0200, Kurt Manucredo wrote:
> On Tue, 1 Jun 2021 17:43:24 +0200, Greg KH <gregkh at linuxfoundation.org> wrote:
> > 
> > On Tue, Jun 01, 2021 at 04:33:09PM +0200, Kurt Manucredo wrote:
> > > Fix shift-out-of-bounds in ___bpf_prog_run().
> > 
> > How is this "fixed"?
> > 
> Fix shift-out-of-bounds in ___bpf_prog_run() by adding extra boundary
> check in check_alu_op() in verifier.c.

Great, say this in the changelog text.

> > > 
> > > UBSAN: shift-out-of-bounds in kernel/bpf/core.c:1414:2
> > > shift exponent 248 is too large for 32-bit type 'unsigned int'
> > 
> > What is this from?
> 
> https://syzkaller.appspot.com/bug?id=edb51be4c9a320186328893287bb30d5eed09231

You should provide this link in the changelog text.

> > Any reason you didn't cc: the bpf maintainers and developers?
> > 
> Yes. I send them to you, the mentees mailing list and Shuah, first, for
> review, comment and help. Is this not okay? 

Ok, didn't know what you were wanting here, you can always ask questions
like this below the --- line of a patch.

> > > Reported-by: syzbot+bed360704c521841c85d at syzkaller.appspotmail.com
> > 
> > Does this pass the syzbot testing?
> 
> Yes, it says 'OK' in the 'Result' column at:
> https://syzkaller.appspot.com/bug?id=edb51be4c9a320186328893287bb30d5eed09231

You should also say something like "passes the syzbot reproducer test"
in the changelog text as well.

> But at this point I cannot say if this is right. Should I send the next
> version to everyone?

Please do!

thanks,

greg k-h


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