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Fri, 5 Jun 2026 13:45:17 -0400 (EDT) Date: Fri, 5 Jun 2026 19:45:15 +0200 From: Marek =?utf-8?Q?Marczykowski-G=C3=B3recki?= To: Mario Limonciello Cc: Yazen Ghannam , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , "open list:AMD NODE DRIVER" , regressions@lists.linux.dev Subject: Re: kernel NULL pointer dereference in quirk_clear_strap_no_soft_reset_dev2_f0 -> amd_smn_read Message-ID: References: <68d86871-12f2-4de1-81aa-dbc9e12b6f91@amd.com> <2535f876-adea-41f1-bf92-a2f15a1eb157@amd.com> Precedence: bulk X-Mailing-List: regressions@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="IjUa0iNkCasjSUIX" Content-Disposition: inline In-Reply-To: <2535f876-adea-41f1-bf92-a2f15a1eb157@amd.com> --IjUa0iNkCasjSUIX Content-Type: text/plain; protected-headers=v1; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Date: Fri, 5 Jun 2026 19:45:15 +0200 From: Marek =?utf-8?Q?Marczykowski-G=C3=B3recki?= To: Mario Limonciello Cc: Yazen Ghannam , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , "open list:AMD NODE DRIVER" , regressions@lists.linux.dev Subject: Re: kernel NULL pointer dereference in quirk_clear_strap_no_soft_reset_dev2_f0 -> amd_smn_read On Fri, Jun 05, 2026 at 12:36:29PM -0500, Mario Limonciello wrote: >=20 >=20 > On 6/5/26 12:34, Marek Marczykowski-G=C3=B3recki wrote: > > On Mon, Jan 12, 2026 at 08:47:50PM -0600, Mario Limonciello wrote: > > >=20 > > >=20 > > > On 1/12/2026 7:01 PM, Marek Marczykowski-G=C3=B3recki wrote: > > > > Hi, > > > >=20 > > > > I've got a report that kernel 6.17.9 crashes when running a Xen HVM= domU > > > > with AMD Raphael/Granite Ridge USB controller passed through. > > > > It worked correctly in 6.12.59. Between those versions, I don't see= any > > > > relevant change to quirk_clear_strap_no_soft_reset_dev2_f0() functi= on, > > > > but the AMD node driver did got some changes, so my guess is one of= them > > > > is to blame. I know the good-bad range is huge, but there aren't th= at > > > > many changes to the AMD node driver in this range. > > >=20 > > > Is this perhaps a case that only the USB controller was passed throug= h but > > > that the root controller wasn't? That would lead to a case that > > > amd_smn_init() was never called and thus amd_roots was not initialized > > > properly. > > >=20 > > > So it would be a NULL pointer deref. If that's correct, something li= ke this > > > should work to avoid it. > > >=20 > > > diff --git a/arch/x86/kernel/amd_node.c b/arch/x86/kernel/amd_node.c > > > index 3d0a4768d603c..894823b444d47 100644 > > > --- a/arch/x86/kernel/amd_node.c > > > +++ b/arch/x86/kernel/amd_node.c > > > @@ -91,6 +91,11 @@ static int __amd_smn_rw(u8 i_off, u8 d_off, u16 no= de, u32 > > > address, u32 *value, b > > > if (node >=3D amd_num_nodes()) > > > return err; > > >=20 > > > + if (!amd_roots) { > > > + pr_warn("AMD SMN roots not initialized.\n"); > > > + return err; > > > + } > > > + > > > root =3D amd_roots[node]; > > > if (!root) > > > return err; > >=20 > > Thanks, I finally got confirmation from affected user that this patch > > fixes the issue. From what I understand, adbf61cc47cb ("x86/acpi/boot: = Correct > > acpi_is_processor_usable() check again") was not enough. > >=20 > > > > Original report at (with full kernel log etc): https://forum.qubes-= os.org/t/yet-another-usb-keyboard-thread/38355/8 > >=20 >=20 > There's another patch being discussed. Could this help? >=20 > https://lore.kernel.org/all/20260602184823.GKah8ld2QJLm28xoa9@fat_crate.l= ocal/ Especially with 2/2 patch there, yes, looks like it would help too. --=20 Best Regards, Marek Marczykowski-G=C3=B3recki Invisible Things Lab --IjUa0iNkCasjSUIX Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhrpukzGPukRmQqkK24/THMrX1ywFAmojCysACgkQ24/THMrX 1yzTgwf/UvhLPdvx9+R09bwcO8tat1gTx6fT/kJGtTtN5tGL8K621az2TJdHnWQg 5PHim6m+2m3EIJV5ws7zz47GbsyzJq2R4/bpL4sLjEgm/yEFYFNy5EElnjsNqOTL +b8rSSWOFK+aKA9eOYh76vUW/P5UE9Phjcy9tRk7S93TDabIqWnlFkkQdM/D3hv8 I2ZnPTTY1bkUET922x1yL29zPzhyWRfSY1g8ZPPj5FOEgn9vx+5kqEREJf1Qj8DW qC5fBqzTjQ58odqKnxdJDLOa7WzbvUloX/qYtpDqw7jfQSPst9jzGkloEosSoPRQ QF4o4Ylc0V78yg+VOY5eNDoZ+/UjxQ== =a3ky -----END PGP SIGNATURE----- --IjUa0iNkCasjSUIX--