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Fri, 5 Jun 2026 19:37:05 -0400 (EDT) Date: Sat, 6 Jun 2026 01:37:03 +0200 From: Marek =?utf-8?Q?Marczykowski-G=C3=B3recki?= To: Borislav Petkov Cc: Mario Limonciello , 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: <2535f876-adea-41f1-bf92-a2f15a1eb157@amd.com> <20260605211543.GFaiM8f2Ee2r5hMYXW@fat_crate.local> <20260605222648.GAaiNNKAr3mtWsMr7e@fat_crate.local> <20260605230949.GBaiNXPZ2ztjVL7DBg@fat_crate.local> 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="ysrED8OdaRdFsXQO" Content-Disposition: inline In-Reply-To: <20260605230949.GBaiNXPZ2ztjVL7DBg@fat_crate.local> --ysrED8OdaRdFsXQO Content-Type: text/plain; protected-headers=v1; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Date: Sat, 6 Jun 2026 01:37:03 +0200 From: Marek =?utf-8?Q?Marczykowski-G=C3=B3recki?= To: Borislav Petkov Cc: Mario Limonciello , 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 04:09:49PM -0700, Borislav Petkov wrote: > On Sat, Jun 06, 2026 at 12:40:20AM +0200, Marek Marczykowski-G=C3=B3recki= wrote: > > There is nothing here that would prevent amd_smn_read() being called > > inside a guest... >=20 > Yah, there should've been... >=20 > Anyway, something like the untested below, pls give it a run. >=20 > Thx. >=20 > --- > diff --git a/arch/x86/kernel/amd_node.c b/arch/x86/kernel/amd_node.c > index 0be01725a2a4..52eff7fac667 100644 > --- a/arch/x86/kernel/amd_node.c > +++ b/arch/x86/kernel/amd_node.c =2E.. > @@ -311,6 +324,10 @@ static int __init amd_smn_init(void) > smn_exclusive =3D true; > =20 > return 0; > + > +err_out: > + amd_node_off =3D true; > + return err; > } > =20 > fs_initcall(amd_smn_init); Is it actually guaranteed to run before PCI fixups? They are done via fs_initcall_sync. IMO it would be safer to guard __amd_smn_rw() with something that would also detect calls before amd_smn_init() is called. Like using smn_exclusive in the Penny's patch, or amd_roots in the Mario's patch. That said, amd_smn_read() called before amd_smn_init() would (should?) fail anyway, even in non-virtualized case. So, maybe this approach (still crash on NULL ptr when called before amd_smn_init()) is acceptable? --=20 Best Regards, Marek Marczykowski-G=C3=B3recki Invisible Things Lab --ysrED8OdaRdFsXQO Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhrpukzGPukRmQqkK24/THMrX1ywFAmojXaAACgkQ24/THMrX 1yylhQf/bi9udZKsz55ESML7pTNGlwliUgrQvzgCii6iA16A19QZfkp4S+KXOzHp ppW56RlvhG/6nol92xp4M1K1adfFpLuTf8bt+LXNWm7AHnwBWcmQEEDxnsw5WSGf TFjlTgUpTerARvHj37PsRXzunBtTllbATmc7+rL/gG/FVbJWUDNKu7k2ISge3S8x 1whJ0d95tMBr7sYPykMGWOPPGzp14EPkitCxGyVsMhgXK62QBUrRKLncHt4wOZ02 h3YgXp+VphDP5cfuSwvFJ3haCfRufljjlu3plMwTfgU8SFIW2EsL9RlJqb2FYjbX LDyBW4Fl1hgwAg9UYCYIoWEyH1l/1g== =EMRC -----END PGP SIGNATURE----- --ysrED8OdaRdFsXQO--