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Fri, 5 Jun 2026 13:34:05 -0400 (EDT) Date: Fri, 5 Jun 2026 19:34:00 +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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="uImcWHheh5RHcjOk" Content-Disposition: inline In-Reply-To: <68d86871-12f2-4de1-81aa-dbc9e12b6f91@amd.com> --uImcWHheh5RHcjOk Content-Type: text/plain; protected-headers=v1; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Date: Fri, 5 Jun 2026 19:34:00 +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 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() function, > > 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 that > > many changes to the AMD node driver in this range. >=20 > Is this perhaps a case that only the USB controller was passed through 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 like t= his > 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 node, = 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; Thanks, I finally got confirmation from affected user that this patch fixes the issue. From what I understand, adbf61cc47cb ("x86/acpi/boot: Corr= ect acpi_is_processor_usable() check again") was not enough. > > Original report at (with full kernel log etc): https://forum.qubes-os.o= rg/t/yet-another-usb-keyboard-thread/38355/8 --=20 Best Regards, Marek Marczykowski-G=C3=B3recki Invisible Things Lab --uImcWHheh5RHcjOk Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhrpukzGPukRmQqkK24/THMrX1ywFAmojCIgACgkQ24/THMrX 1yzzhAf+Iogj+9gfdBQuxwl4pGyWGFXAiJz1gEVKYHbtWX0ib7w+emSzELpQ5rWb yT0U0sqUIG7X4QrpSu4wA7x4RoA9a0EQ8dl5PdILGy9X5cxKKnuZ2S6G2sFUKrGh j0uAo6nyuXeVTqxl3RNeMUyzjzPLItK8EopJbegj6C3+FnUDBR3QqpDBKDkwzrku mPKLxcE+aj1/mH2Lmn3dhcMic60UJna0Fq5Om4GC926d0TYkd8eWgqkS0WUSjkQu TrZXn/weKhCv7JdAI6oPJYAa/S62+lTi6WsabYRBFfhCilj8T2T/Gad8vsTvdg3G +DqW/cuy/J0b9xUC84Mryzz3I0wL+A== =Ivh3 -----END PGP SIGNATURE----- --uImcWHheh5RHcjOk--