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Date: Fri, 9 Dec 2022 10:14:21 -0800 From: Dan Williams <dan.j.williams@...el.com> To: Luis Chamberlain <mcgrof@...nel.org>, <alison.schofield@...el.com>, <vishal.l.verma@...el.com>, <ira.weiny@...el.com>, <bwidawsk@...nel.org>, <dan.j.williams@...el.com> CC: <dave@...olabs.net>, <a.manzanares@...sung.com>, <mcgrof@...nel.org>, <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org> Subject: RE: [PATCH] cxl/acpi: fix null dereference on probe for missing ACPI_COMPANION() Luis Chamberlain wrote: > Simply loading cxl_test ends up triggering a null pointer dereference > on next-20221207, and it happens because the fetched ACPI_COMPANION() can > end up not correct / missing. As with other code which uses ACPI_COMPANION() > (drivers/acpi/device_pm.c comes to mind) be defensive over the assumption > the companion is always present and bail right away. > > This can be easily reproduced with kdevops [0] with linux next-20221207 [1] > and cxl enabled workflows: > > make menuconfig # enable cxl and linux-next > make # sets up variables, builds qemu from source > make linux # builds and install next-20221207 > make cxl # installs cxl tool > make cxl-test-probe # loads cxl_test > > The oops: > > # modprobe cxl_test > No TPM handle discovered. > failed to open file /etc/ndctl/keys/nvdimm-master.blob: No such file or directory > > [0] https://github.com/linux-kdevops/kdevops > [1] https://github.com/linux-kdevops/kdevops/blob/master/playbooks/roles/bootlinux/templates/config-next-20221207 > > cxl_mock: loading out-of-tree module taints kernel. > cxl_mock: loading test module taints kernel. > cxl_mem mem0: at cxl_root_port.0 no parent for dport: platform > cxl_mem mem1: at cxl_root_port.1 no parent for dport: platform > cxl_mem mem2: at cxl_root_port.2 no parent for dport: platform > cxl_mem mem3: at cxl_root_port.3 no parent for dport: platform > cxl_mem mem4: at cxl_root_port.0 no parent for dport: platform > cxl_mem mem5: at cxl_root_port.1 no parent for dport: platform > cxl_mem mem6: at cxl_root_port.2 no parent for dport: platform > cxl_mem mem7: at cxl_root_port.3 no parent for dport: platform > cxl_mem mem8: at cxl_root_port.4 no parent for dport: platform > cxl_mem mem9: at cxl_root_port.4 no parent for dport: platform > cxl_mem mem10: CXL port topology not found > BUG: kernel NULL pointer dereference, address: 00000000000002c0 > #PF: supervisor read access in kernel mode > #PF: error_code(0x0000) - not-present page > PGD 0 P4D 0 > Oops: 0000 [#1] PREEMPT SMP PTI > CPU: 4 PID: 1644 Comm: systemd-udevd Kdump: loaded Tainted: G O N 6.1.0-rc8-next-20221207 #5 > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.1-0-g3208b098f51a-prebuilt.qemu.org 04/01/2014 > RIP: 0010:cxl_acpi_probe+0xeb/0x2f0 [cxl_acpi] > Code: ff ff ff 48 c7 40 08 ff ff ff ff 48 c7 40 18 00 02 00 00 e8 57 29 fd ff 49 89 c7 41 89 c4 48 3d 00 f0 ff ff 0f 87 73 ff ff ff <49> 8b bd c0 02 00 00 48 c7 c1 c0 64 e4 c0 48 89 c2 31 f6 e8 bd f1 > RSP: 0018:ffffbe6d008b7c30 EFLAGS: 00010287 > RAX: ffff97a7c6e01000 RBX: ffff97a7c51fd810 RCX: 0000000000000000 > RDX: 0000000000000001 RSI: 0000000000000282 RDI: 00000000ffffffff > RBP: 0000000000000000 R08: ffff97a7c51fdaa8 R09: 0000000000000010 > R10: 0000000000000002 R11: 00000000000013c7 R12: 00000000c6e01000 > R13: 0000000000000000 R14: ffff97a7d9c653a8 R15: ffff97a7c6e01000 > FS: 00007f34b038ed00(0000) GS:ffff97a83bd00000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00000000000002c0 CR3: 0000000102f7e005 CR4: 0000000000770ee0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > PKRU: 55555554 > Call Trace: > <TASK> > ? kernfs_create_link+0x5d/0xa0 > platform_probe+0x41/0x90 > really_probe+0xdb/0x380 > ? pm_runtime_barrier+0x50/0x90 > __driver_probe_device+0x78/0x170 > driver_probe_device+0x1f/0x90 > __driver_attach+0xce/0x1c0 > ? __pfx___driver_attach+0x10/0x10 > bus_for_each_dev+0x73/0xc0 > bus_add_driver+0x1ae/0x200 > driver_register+0x89/0xe0 > ? __pfx_init_module+0x10/0x10 [cxl_acpi] > do_one_initcall+0x43/0x220 > ? kmalloc_trace+0x26/0x90 > do_init_module+0x4a/0x1f0 > __do_sys_init_module+0x17f/0x1b0 > do_syscall_64+0x37/0x90 > entry_SYSCALL_64_after_hwframe+0x72/0xdc > RIP: 0033:0x7f34b061baaa > Code: 48 8b 0d 59 83 0c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 49 89 ca b8 af 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 26 83 0c 00 f7 d8 64 89 01 48 > RSP: 002b:00007fff6a198408 EFLAGS: 00000246 ORIG_RAX: 00000000000000af > RAX: ffffffffffffffda RBX: 00005635afc7e5e0 RCX: 00007f34b061baaa > RDX: 00007f34b07a5efd RSI: 0000000000060a29 RDI: 00005635afdd6510 > RBP: 00007f34b07a5efd R08: 000000000001f5b3 R09: 0000000000000000 > R10: 000000000000eb81 R11: 0000000000000246 R12: 00005635afdd6510 > R13: 0000000000000000 R14: 00005635afca6f40 R15: 00005635af874e50 > </TASK> > Modules linked in: cxl_acpi(+) cxl_pmem cxl_mem cxl_port cxl_mock_mem(ON) cxl_test(ON) cxl_mock(ON) cxl_core libnvdimm cbc encrypted_keys kvm_intel kvm 9p netfs irqbypass crct10dif_pclmul ghash_clmulni_intel sha512_ssse3 sha512_generic aesni_intel crypto_simd cryptd cirrus drm_shmem_helper 9pnet_virtio virtio_balloon i6300esb drm_kms_helper joydev evdev button serio_raw drm configfs ip_tables x_tables autofs4 ext4 crc16 mbcache jbd2 btrfs blake2b_generic raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c crc32c_generic raid1 raid0 md_mod virtio_net net_failover virtio_blk failover psmouse virtio_pci virtio_pci_legacy_dev nvme virtio_pci_modern_dev crc32_pclmul nvme_core virtio crc32c_intel t10_pi virtio_ring crc64_rocksoft crc64 > > And gdb: > > (gdb) l *(cxl_acpi_probe+0xeb) > 0xa8b is in cxl_acpi_probe (tools/testing/cxl/../../../drivers/cxl/acpi.c:648). > 643 > 644 root_port = devm_cxl_add_port(host, host, CXL_RESOURCE_NONE, NULL); > 645 if (IS_ERR(root_port)) > 646 return PTR_ERR(root_port); > 647 > 648 rc = bus_for_each_dev(adev->dev.bus, NULL, root_port, > 649 add_host_bridge_dport); > 650 if (rc < 0) > 651 return rc; > 652 > > Signed-off-by: Luis Chamberlain <mcgrof@...nel.org> > --- > > Note: kdevops also suports now the target: > > make cxl-test-meson > > But that does not *at least* crash the kernel although the tests fail too... > This is likely a misconfiguration of some sort, but the same kernel > works fine when I enable a Type 3 memory device (also supported on > kdevops via CONFIG_QEMU_ENABLE_CXL_DEMO_TOPOLOGY_1). This test was run > without that enabled, so a naked cxl system. > > Even if it *was* a mis-configuration, such things should not crash the kernel. > > drivers/cxl/acpi.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c > index ad0849af42d7..cf5d1a455efc 100644 > --- a/drivers/cxl/acpi.c > +++ b/drivers/cxl/acpi.c > @@ -633,6 +633,9 @@ static int cxl_acpi_probe(struct platform_device *pdev) > struct acpi_device *adev = ACPI_COMPANION(host); > struct cxl_cfmws_context ctx; > > + if (!adev) > + return -ENODEV; > + I can hear the static analysis bots sharpening their knives at the thought that ACPI platform device drivers need to check the result of ACPI_COMPANION(). This is clearly a cxl_test bug, not something the cxl_acpi driver should ever worry about. If ACPI_COMPANION() is failing for the mock platform device then there are bigger problems afoot and this is just a band-aid until the next failure. I'll try booting linux-next, because cxl_test is working for me just testing the tip of cxl.git/next.
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