Re: [PATCH] crypto: ccp - Fix null pointer dereference in __sev_platform_shutdown_locked

[Liam Merwick <liam.merwick@oracle.com>]

On 25/01/2024 23:12, Kim Phillips wrote:
> The SEV platform device can be shutdown with a null psp_master,
> e.g., using DEBUG_TEST_DRIVER_REMOVE.  Found using KASAN:
> 
> [  137.148210] ccp 0000:23:00.1: enabling device (0000 -> 0002)
> [  137.162647] ccp 0000:23:00.1: no command queues available
> [  137.170598] ccp 0000:23:00.1: sev enabled
> [  137.174645] ccp 0000:23:00.1: psp enabled
> [  137.178890] general protection fault, probably for non-canonical address 0xdffffc000000001e: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC KASAN NOPTI
> [  137.182693] KASAN: null-ptr-deref in range [0x00000000000000f0-0x00000000000000f7]
> [  137.182693] CPU: 93 PID: 1 Comm: swapper/0 Not tainted 6.8.0-rc1+ #311
> [  137.182693] RIP: 0010:__sev_platform_shutdown_locked+0x51/0x180
> [  137.182693] Code: 08 80 3c 08 00 0f 85 0e 01 00 00 48 8b 1d 67 b6 01 08 48 b8 00 00 00 00 00 fc ff df 48 8d bb f0 00 00 00 48 89 f9 48 c1 e9 03 <80> 3c 01 00 0f 85 fe 00 00 00 48 8b 9b f0 00 00 00 48 85 db 74 2c
> [  137.182693] RSP: 0018:ffffc900000cf9b0 EFLAGS: 00010216
> [  137.182693] RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 000000000000001e
> [  137.182693] RDX: 0000000000000000 RSI: 0000000000000008 RDI: 00000000000000f0
> [  137.182693] RBP: ffffc900000cf9c8 R08: 0000000000000000 R09: fffffbfff58f5a66
> [  137.182693] R10: ffffc900000cf9c8 R11: ffffffffac7ad32f R12: ffff8881e5052c28
> [  137.182693] R13: ffff8881e5052c28 R14: ffff8881758e43e8 R15: ffffffffac64abf8
> [  137.182693] FS:  0000000000000000(0000) GS:ffff889de7000000(0000) knlGS:0000000000000000
> [  137.182693] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [  137.182693] CR2: 0000000000000000 CR3: 0000001cf7c7e000 CR4: 0000000000350ef0
> [  137.182693] Call Trace:
> [  137.182693]  <TASK>
> [  137.182693]  ? show_regs+0x6c/0x80
> [  137.182693]  ? __die_body+0x24/0x70
> [  137.182693]  ? die_addr+0x4b/0x80
> [  137.182693]  ? exc_general_protection+0x126/0x230
> [  137.182693]  ? asm_exc_general_protection+0x2b/0x30
> [  137.182693]  ? __sev_platform_shutdown_locked+0x51/0x180
> [  137.182693]  sev_firmware_shutdown.isra.0+0x1e/0x80
> [  137.182693]  sev_dev_destroy+0x49/0x100
> [  137.182693]  psp_dev_destroy+0x47/0xb0
> [  137.182693]  sp_destroy+0xbb/0x240
> [  137.182693]  sp_pci_remove+0x45/0x60
> [  137.182693]  pci_device_remove+0xaa/0x1d0
> [  137.182693]  device_remove+0xc7/0x170
> [  137.182693]  really_probe+0x374/0xbe0
> [  137.182693]  ? srso_return_thunk+0x5/0x5f
> [  137.182693]  __driver_probe_device+0x199/0x460
> [  137.182693]  driver_probe_device+0x4e/0xd0
> [  137.182693]  __driver_attach+0x191/0x3d0
> [  137.182693]  ? __pfx___driver_attach+0x10/0x10
> [  137.182693]  bus_for_each_dev+0x100/0x190
> [  137.182693]  ? __pfx_bus_for_each_dev+0x10/0x10
> [  137.182693]  ? __kasan_check_read+0x15/0x20
> [  137.182693]  ? srso_return_thunk+0x5/0x5f
> [  137.182693]  ? _raw_spin_unlock+0x27/0x50
> [  137.182693]  driver_attach+0x41/0x60
> [  137.182693]  bus_add_driver+0x2a8/0x580
> [  137.182693]  driver_register+0x141/0x480
> [  137.182693]  __pci_register_driver+0x1d6/0x2a0
> [  137.182693]  ? srso_return_thunk+0x5/0x5f
> [  137.182693]  ? esrt_sysfs_init+0x1cd/0x5d0
> [  137.182693]  ? __pfx_sp_mod_init+0x10/0x10
> [  137.182693]  sp_pci_init+0x22/0x30
> [  137.182693]  sp_mod_init+0x14/0x30
> [  137.182693]  ? __pfx_sp_mod_init+0x10/0x10
> [  137.182693]  do_one_initcall+0xd1/0x470
> [  137.182693]  ? __pfx_do_one_initcall+0x10/0x10
> [  137.182693]  ? parameq+0x80/0xf0
> [  137.182693]  ? srso_return_thunk+0x5/0x5f
> [  137.182693]  ? __kmalloc+0x3b0/0x4e0
> [  137.182693]  ? kernel_init_freeable+0x92d/0x1050
> [  137.182693]  ? kasan_populate_vmalloc_pte+0x171/0x190
> [  137.182693]  ? srso_return_thunk+0x5/0x5f
> [  137.182693]  kernel_init_freeable+0xa64/0x1050
> [  137.182693]  ? __pfx_kernel_init+0x10/0x10
> [  137.182693]  kernel_init+0x24/0x160
> [  137.182693]  ? __switch_to_asm+0x3e/0x70
> [  137.182693]  ret_from_fork+0x40/0x80
> [  137.182693]  ? __pfx_kernel_init+0x10/0x10
> [  137.182693]  ret_from_fork_asm+0x1b/0x30
> [  137.182693]  </TASK>
> [  137.182693] Modules linked in:
> [  137.538483] ---[ end trace 0000000000000000 ]---
> 
> Fixes: 1b05ece0c9315 ("crypto: ccp - During shutdown, check SEV data pointer before using")

checkpatch warns about SHA1 of Fixes: having more than 12 chars...

However, although 1b05ece0c931 is the last commit to change this
functionality, I think this issue exists prior to that.

5441a07a127f ("crypto: ccp - shutdown SEV firmware on kexec")
might be more appropriate so that it'd get applied to linux-5.15.y
(where 1b05ece0c931 and 5441a07a127f have been backported to also)
This patch applies cleanly to linux-5.15.y.


> Cc: stable@vger.kernel.org
> Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
> Signed-off-by: Kim Phillips <kim.phillips@amd.com>

Code changes LGTM, so
Reviewed-by: Liam Merwick <liam.merwick@oracle.com>


> ---
>   drivers/crypto/ccp/sev-dev.c | 10 ++++++++--
>   1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
> index fcaccd0b5a65..53b217a62104 100644
> --- a/drivers/crypto/ccp/sev-dev.c
> +++ b/drivers/crypto/ccp/sev-dev.c
> @@ -534,10 +534,16 @@ EXPORT_SYMBOL_GPL(sev_platform_init);
>   
>   static int __sev_platform_shutdown_locked(int *error)
>   {
> -	struct sev_device *sev = psp_master->sev_data;
> +	struct psp_device *psp = psp_master;
> +	struct sev_device *sev;
>   	int ret;
>   
> -	if (!sev || sev->state == SEV_STATE_UNINIT)
> +	if (!psp || !psp->sev_data)
> +		return 0;
> +
> +	sev = psp->sev_data;
> +
> +	if (sev->state == SEV_STATE_UNINIT)
>   		return 0;
>   
>   	ret = __sev_do_cmd_locked(SEV_CMD_SHUTDOWN, NULL, error);