linux-kernel - Re: [PATCH] crypto: ccp: Properly unregister /dev/sev on sev PLATFORM

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Message-ID: <1c6365b1-c134-d1a9-9fb2-22b26abf1a87@amd.com>
Date: Thu, 22 Aug 2024 10:17:34 -0500
From: "Paluri, PavanKumar" <papaluri@....com>
To: linux-crypto@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, Tom Lendacky <thomas.lendacky@....com>,
 Ashish Kalra <ashish.kalra@....com>, John Allen <john.allen@....com>,
 Herbert Xu <herbert@...dor.apana.org.au>,
 "David S . Miller" <davem@...emloft.net>, stable@...r.kernel.org
Subject: Re: [PATCH] crypto: ccp: Properly unregister /dev/sev on sev
 PLATFORM_STATUS failure



On 8/15/2024 7:25 AM, Pavan Kumar Paluri wrote:
> In case of sev PLATFORM_STATUS failure, sev_get_api_version() fails
> resulting in sev_data field of psp_master nulled out. This later becomes
> a problem when unloading the ccp module because the device has not been
> unregistered (via misc_deregister()) before clearing the sev_data field
> of psp_master. As a result, on reloading the ccp module, a duplicate
> device issue is encountered as can be seen from the dmesg log below.
> 
> on reloading ccp module via modprobe ccp
> 
> Call Trace:
>   <TASK>
>   dump_stack_lvl+0xd7/0xf0
>   dump_stack+0x10/0x20
>   sysfs_warn_dup+0x5c/0x70
>   sysfs_create_dir_ns+0xbc/0xd
>   kobject_add_internal+0xb1/0x2f0
>   kobject_add+0x7a/0xe0
>   ? srso_alias_return_thunk+0x5/0xfbef5
>   ? get_device_parent+0xd4/0x1e0
>   ? __pfx_klist_children_get+0x10/0x10
>   device_add+0x121/0x870
>   ? srso_alias_return_thunk+0x5/0xfbef5
>   device_create_groups_vargs+0xdc/0x100
>   device_create_with_groups+0x3f/0x60
>   misc_register+0x13b/0x1c0
>   sev_dev_init+0x1d4/0x290 [ccp]
>   psp_dev_init+0x136/0x300 [ccp]
>   sp_init+0x6f/0x80 [ccp]
>   sp_pci_probe+0x2a6/0x310 [ccp]
>   ? srso_alias_return_thunk+0x5/0xfbef5
>   local_pci_probe+0x4b/0xb0
>   work_for_cpu_fn+0x1a/0x30
>   process_one_work+0x203/0x600
>   worker_thread+0x19e/0x350
>   ? __pfx_worker_thread+0x10/0x10
>   kthread+0xeb/0x120
>   ? __pfx_kthread+0x10/0x10
>   ret_from_fork+0x3c/0x60
>   ? __pfx_kthread+0x10/0x10
>   ret_from_fork_asm+0x1a/0x30
>   </TASK>
>   kobject: kobject_add_internal failed for sev with -EEXIST, don't try to register things with the same name in the same directory.
>   ccp 0000:22:00.1: sev initialization failed
>   ccp 0000:22:00.1: psp initialization failed
>   ccp 0000:a2:00.1: no command queues available
>   ccp 0000:a2:00.1: psp enabled
> 
> Address this issue by unregistering the /dev/sev before clearing out
> sev_data in case of PLATFORM_STATUS failure.
> 
> Fixes: 200664d5237f ("crypto: ccp: Add Secure Encrypted Virtualization (SEV) command support")
> Cc: stable@...r.kernel.org
> Signed-off-by: Pavan Kumar Paluri <papaluri@....com>
> ---
>  drivers/crypto/ccp/sev-dev.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
> index 9810edbb272d..5f63d2018649 100644
> --- a/drivers/crypto/ccp/sev-dev.c
> +++ b/drivers/crypto/ccp/sev-dev.c
> @@ -2410,6 +2410,8 @@ void sev_pci_init(void)
>  	return;
>  
>  err:
> +	sev_dev_destroy(psp_master);
> +
>  	psp_master->sev_data = NULL;
>  }
>  
> 
> base-commit: b8c7cbc324dc17b9e42379b42603613580bec2d8

A gentle reminder,

Thanks,
Pavan