Well, this is embarrassing. There's no compiler bug, just me being confused, because I looked at handle instead of *handle. The stack protector thing was of course a red herring - it changed what is on the stack and where... If the patch below will be corrupted by the Gmail interface, I also pushed it here: https://github.com/marcinslusarz/linux/tree/soundwire_fix ---- From: =?UTF-8?q?Marcin=20=C5=9Alusarz?= <marcin.slusarz@xxxxxxxxx> Subject: [PATCH] soundwire: intel: fix possible crash when no device is detected acpi_walk_namespace can return success without executing our callback which initializes info->handle. If the random value in this structure is a valid address (which is on the stack, so it's quite possible), then nothing bad will happen, because: sdw_intel_scan_controller -> acpi_bus_get_device -> acpi_get_device_data -> acpi_get_data_full -> acpi_ns_validate_handle will reject this handle. However, if the value from the stack doesn't point to a valid address, we get this: BUG: kernel NULL pointer dereference, address: 0000000000000050 PGD 0 P4D 0 Oops: 0000 [#1] SMP NOPTI CPU: 6 PID: 472 Comm: systemd-udevd Tainted: G W 5.10.0-1-amd64 #1 Debian 5.10.4-1 Hardware name: HP HP Pavilion Laptop 15-cs3xxx/86E2, BIOS F.05 01/01/2020 RIP: 0010:acpi_ns_validate_handle+0x1a/0x23 Code: 00 48 83 c4 10 5b 5d 41 5c 41 5d 41 5e 41 5f c3 0f 1f 44 00 00 48 8d 57 ff 48 89 f8 48 83 fa fd 76 08 48 8b 05 0c b8 67 01 c3 <80> 7f 08 0f 74 02 31 c0 c3 0f 1f 44 00 00 48 8b 3d f6 b7 67 01 e8 RSP: 0000:ffffc388807c7b20 EFLAGS: 00010213 RAX: 0000000000000048 RBX: ffffc388807c7b70 RCX: 0000000000000000 RDX: 0000000000000047 RSI: 0000000000000246 RDI: 0000000000000048 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: ffffffffc0f5f4d1 R11: ffffffff8f0cb268 R12: 0000000000001001 R13: ffffffff8e33b160 R14: 0000000000000048 R15: 0000000000000000 FS: 00007f24548288c0(0000) GS:ffff9f781fb80000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000050 CR3: 0000000106158004 CR4: 0000000000770ee0 PKRU: 55555554 Call Trace: acpi_get_data_full+0x4d/0x92 acpi_bus_get_device+0x1f/0x40 sdw_intel_acpi_scan+0x59/0x230 [soundwire_intel] ? strstr+0x22/0x60 ? dmi_matches+0x76/0xe0 snd_intel_dsp_driver_probe.cold+0xaf/0x163 [snd_intel_dspcfg] azx_probe+0x7a/0x970 [snd_hda_intel] local_pci_probe+0x42/0x80 ? _cond_resched+0x16/0x40 pci_device_probe+0xfd/0x1b0 really_probe+0x205/0x460 driver_probe_device+0xe1/0x150 device_driver_attach+0xa1/0xb0 __driver_attach+0x8a/0x150 ? device_driver_attach+0xb0/0xb0 ? device_driver_attach+0xb0/0xb0 bus_for_each_dev+0x78/0xc0 bus_add_driver+0x12b/0x1e0 driver_register+0x8b/0xe0 ? 0xffffffffc0f65000 do_one_initcall+0x44/0x1d0 ? do_init_module+0x23/0x250 ? kmem_cache_alloc_trace+0xf5/0x200 do_init_module+0x5c/0x250 __do_sys_finit_module+0xb1/0x110 do_syscall_64+0x33/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xa9 CC: stable@xxxxxxxxxxxxxxx Signed-off-by: Marcin Ślusarz <marcin.slusarz@xxxxxxxxx> --- drivers/soundwire/intel_init.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/soundwire/intel_init.c b/drivers/soundwire/intel_init.c index cabdadb09a1b..bc8520eb385e 100644 --- a/drivers/soundwire/intel_init.c +++ b/drivers/soundwire/intel_init.c @@ -405,11 +405,12 @@ int sdw_intel_acpi_scan(acpi_handle *parent_handle, { acpi_status status; + info->handle = NULL; status = acpi_walk_namespace(ACPI_TYPE_DEVICE, parent_handle, 1, sdw_intel_acpi_cb, NULL, info, NULL); - if (ACPI_FAILURE(status)) + if (ACPI_FAILURE(status) || info->handle == NULL) return -ENODEV; return sdw_intel_scan_controller(info); -- 2.29.2
