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Date: Sun, 10 Sep 2023 19:46:50 +0200
From: Heinrich Schuchardt <heinrich.schuchardt@...onical.com>
To: Ard Biesheuvel <ardb@...nel.org>
Cc: Jeremy Kerr <jk@...abs.org>, Anisse Astier <an.astier@...teo.com>,
linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/1] efivarfs: fix statfs() on efivarfs
On 9/10/23 15:54, Ard Biesheuvel wrote:
> On Sun, 10 Sept 2023 at 15:08, Ard Biesheuvel <ardb@...nel.org> wrote:
>>
>> On Sun, 10 Sept 2023 at 06:53, Heinrich Schuchardt
>> <heinrich.schuchardt@...onical.com> wrote:
>>>
>>> Some firmware (notably U-Boot) provides GetVariable() and
>>> GetNextVariableName() but not QueryVariableInfo().
>>>
>>> With commit d86ff3333cb1 ("efivarfs: expose used and total size") the
>>> statfs syscall was broken for such firmware.
>>>
>>> If QueryVariableInfo() does not exist or returns an error, just report the
>>> file-system size as 0 as statfs_simple() previously did.
>>>
>>> Fixes: d86ff3333cb1 ("efivarfs: expose used and total size")
>>> Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@...onical.com>
>>> ---
>>> v2:
>>> initialize remaining_space to 0
>>
>> Thanks for the patch, and apologies for the oversight.
>>
>>> ---
>>> fs/efivarfs/super.c | 20 ++++++++++++--------
>>> 1 file changed, 12 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c
>>> index e028fafa04f3..3893aae6a9be 100644
>>> --- a/fs/efivarfs/super.c
>>> +++ b/fs/efivarfs/super.c
>>> @@ -29,14 +29,9 @@ static int efivarfs_statfs(struct dentry *dentry, struct kstatfs *buf)
>>> const u32 attr = EFI_VARIABLE_NON_VOLATILE |
>>> EFI_VARIABLE_BOOTSERVICE_ACCESS |
>>> EFI_VARIABLE_RUNTIME_ACCESS;
>>> - u64 storage_space, remaining_space, max_variable_size;
>>> + u64 storage_space, remaining_space = 0, max_variable_size;
>>
>> Shouldn't storage_space be set to 0 too?
>>
>>> efi_status_t status;
>>>
>>> - status = efivar_query_variable_info(attr, &storage_space, &remaining_space,
>>> - &max_variable_size);
>>> - if (status != EFI_SUCCESS)
>>> - return efi_status_to_err(status);
>>> -
>>> /*
>>> * This is not a normal filesystem, so no point in pretending it has a block
>>> * size; we declare f_bsize to 1, so that we can then report the exact value
>>> @@ -44,10 +39,19 @@ static int efivarfs_statfs(struct dentry *dentry, struct kstatfs *buf)
>>> */
>>> buf->f_bsize = 1;
>>> buf->f_namelen = NAME_MAX;
>>> - buf->f_blocks = storage_space;
>>> - buf->f_bfree = remaining_space;
>>> buf->f_type = dentry->d_sb->s_magic;
>>>
>>> + /* Some UEFI firmware does not implement QueryVariable() */
>>> + if (efi_rt_services_supported(EFI_RT_SUPPORTED_QUERY_VARIABLE_INFO)) {
>>> + status = efivar_query_variable_info(attr, &storage_space,
>>> + &remaining_space,
>>> + &max_variable_size);
>>> + if (status == EFI_SUCCESS) {
>>> + buf->f_blocks = storage_space;
>>> + buf->f_bfree = remaining_space;
>>> + }
>>> + }
>>> +
>>
>> I'd prefer not to ignore the error completely here. How about we do
>>
>> --- a/fs/efivarfs/super.c
>> +++ b/fs/efivarfs/super.c
>> @@ -32,10 +32,15 @@ static int efivarfs_statfs(struct dentry *dentry,
>> struct kstatfs *buf)
>> u64 storage_space, remaining_space, max_variable_size;
>> efi_status_t status;
>>
>> - status = efivar_query_variable_info(attr, &storage_space,
>> &remaining_space,
>> - &max_variable_size);
>> - if (status != EFI_SUCCESS)
>> - return efi_status_to_err(status);
>> + /* Some UEFI firmware does not implement QueryVariableInfo() */
>> + storage_space = remaining_space = 0;
>> + if (efi_rt_services_supported(EFI_RT_SUPPORTED_QUERY_VARIABLE_INFO)) {
>> + status = efivar_query_variable_info(attr, &storage_space,
>> + &remaining_space,
>> + &max_variable_size);
>> + if (status != EFI_SUCCESS && status != EFI_UNSUPPORTED)
>> + return efi_status_to_err(status);
>> + }
>>
>> /*
>> * This is not a normal filesystem, so no point in pretending
>> it has a block
>>
>> (no need to resend if you agree)
Hello Ard,
thanks for reviewing.
Raising an error in such a rare circumstance would be ok for me.
>
> Actually, perhaps it would be better to simply fall back to the old
> logic if QueryVariableInfo is not provided:
>
> diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c
> index e028fafa04f3..50b05f1fa974 100644
> --- a/fs/efivarfs/super.c
> +++ b/fs/efivarfs/super.c
> @@ -30,10 +30,15 @@ static int efivarfs_statfs(struct dentry *dentry,
> struct kstatfs *buf)
> EFI_VARIABLE_BOOTSERVICE_ACCESS |
> EFI_VARIABLE_RUNTIME_ACCESS;
> u64 storage_space, remaining_space, max_variable_size;
> - efi_status_t status;
> + efi_status_t status = EFI_UNSUPPORTED;
> +
> + if (efi_rt_services_supported(EFI_RT_SUPPORTED_QUERY_VARIABLE_INFO))
> + status = efivar_query_variable_info(attr, &storage_space,
> + &remaining_space,
> + &max_variable_size);
> + if (status == EFI_UNSUPPORTED)
> + return simple_statfs(dentry, buf);
I would not know why the block size (buf->f_bsize) should depend on the
availability of QueryVariableInfo() (1 vs PAGE_SIZE).
Hence I would prefer your suggestion to just add the error handling
suggested in your previous mail.
Best regards
Heinrich
>
> - status = efivar_query_variable_info(attr, &storage_space,
> &remaining_space,
> - &max_variable_size);
> if (status != EFI_SUCCESS)
> return efi_status_to_err(status);
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