linux-kernel - Re: [PATCH] x86/amd_nb: Check for invalid SMN reads

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 3 Apr 2023 15:40:38 -0400
From:   Yazen Ghannam <yazen.ghannam@....com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     yazen.ghannam@....com, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/amd_nb: Check for invalid SMN reads

On 4/3/23 15:32, Borislav Petkov wrote:
> On Mon, Apr 03, 2023 at 04:42:44PM +0000, Yazen Ghannam wrote:
>>  int amd_smn_read(u16 node, u32 address, u32 *value)
>>  {
>> -	return __amd_smn_rw(node, address, value, false);
>> +	int err = __amd_smn_rw(node, address, value, false);
>> +
>> +	if (PCI_POSSIBLE_ERROR(*value)) {
>> +		err = -ENODEV;
>> +		*value = 0;
>> +	}
> 
> Why not put this check in __amd_smn_rw()?
> 

I don't think pci_write_config*() sets the PCI Error response like
pci_read_config(), AFAICT.

I think to solve the writes-ignored problem, we'd need to do another read and
compare it to what we intended to write. That could go into amd_smn_write(),
if needed. Unless the PCI kernel API has something like this.

Thanks,
Yazen