Re: CVE-2023-52665: powerpc/ps3_defconfig: Disable PPC64_BIG_ENDIAN_ELF_ABI_V2

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Tue, May 21, 2024 at 09:47:33AM +1000, Michael Ellerman wrote:
> Greg Kroah-Hartman <gregkh@linuxfoundation.org> writes:
> > On Mon, May 20, 2024 at 05:35:32PM +0900, Geoff Levand wrote:
> >> On 5/20/24 16:04, Michael Ellerman wrote:
> >> > Greg Kroah-Hartman <gregkh@linuxfoundation.org> writes:
> >> >> Description
> >> >> ===========
> >> >>
> >> >> In the Linux kernel, the following vulnerability has been resolved:
> >> >>
> >> >> powerpc/ps3_defconfig: Disable PPC64_BIG_ENDIAN_ELF_ABI_V2
> >> >>
> >> >> Commit 8c5fa3b5c4df ("powerpc/64: Make ELFv2 the default for big-endian
> >> >> builds"), merged in Linux-6.5-rc1 changes the calling ABI in a way
> >> >> that is incompatible with the current code for the PS3's LV1 hypervisor
> >> >> calls.
> >> >>
> >> >> This change just adds the line '# CONFIG_PPC64_BIG_ENDIAN_ELF_ABI_V2 is not set'
> >> >> to the ps3_defconfig file so that the PPC64_ELF_ABI_V1 is used.
> >> >>
> >> >> Fixes run time errors like these:
> >> >>
> >> >>   BUG: Kernel NULL pointer dereference at 0x00000000
> >> >>   Faulting instruction address: 0xc000000000047cf0
> >> >>   Oops: Kernel access of bad area, sig: 11 [#1]
> >> >>   Call Trace:
> >> >>   [c0000000023039e0] [c00000000100ebfc] ps3_create_spu+0xc4/0x2b0 (unreliable)
> >> >>   [c000000002303ab0] [c00000000100d4c4] create_spu+0xcc/0x3c4
> >> >>   [c000000002303b40] [c00000000100eae4] ps3_enumerate_spus+0xa4/0xf8
> >> >>
> >> >> The Linux kernel CVE team has assigned CVE-2023-52665 to this issue.
> >> > 
> >> > IMHO this doesn't warrant a CVE. The crash mentioned above happens at
> >> > boot, so the system is not vulnerable it's just broken :)
> >> 
> >> As Greg says, with PPC64_BIG_ENDIAN_ELF_ABI_V2 enabled the system won't
> >> boot, so there is no chance of a vulnerability.
> >
> > The definition of "vulnerability" from CVE.org is:
> > 	An instance of one or more weaknesses in a Product that can be
> > 	exploited, causing a negative impact to confidentiality, integrity, or
> > 	availability; a set of conditions or behaviors that allows the
> > 	violation of an explicit or implicit security policy.
> >
> > Having a system that does not boot is a "negative impact to
> > availability", which is why this was selected for a CVE.  I.e. if a new
> > kernel update has this problem in it, it would not allow the system to
> > boot correctly.
> 
> I think the key word above is "exploited", implying some sort of
> unauthorised action.
> 
> This bug can cause the system to not boot, but only by someone who
> builds a new kernel and installs it - and if they have permission to do
> that they can just replace the kernel with anything, they don't need a
> bug.
> 
> > But, if the maintainer of the subsystem thinks this should not be
> > assigned a CVE because of this fix, we'll be glad to revoke it.
> >
> > Michael, still want this revoked?
> 
> Yes please.

Now rejected, thanks all for the review!

greg k-h