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Date: Sun, 10 Sep 2023 15:54:05 +0200
From: Ard Biesheuvel <ardb@...nel.org>
To: Heinrich Schuchardt <heinrich.schuchardt@...onical.com>
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 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)
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);
- 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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