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Commit ca0e30dc authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Ingo Molnar
Browse files

efi: Add nonblocking option to efi_query_variable_store() 



The function efi_query_variable_store() may be invoked by
efivar_entry_set_nonblocking(), which itself takes care to only
call a non-blocking version of the SetVariable() runtime
wrapper. However, efi_query_variable_store() may call the
SetVariable() wrapper directly, as well as the wrapper for
QueryVariableInfo(), both of which could deadlock in the same
way we are trying to prevent by calling
efivar_entry_set_nonblocking() in the first place.

So instead, modify efi_query_variable_store() to use the
non-blocking variants of QueryVariableInfo() (and give up rather
than free up space if the available space is below
EFI_MIN_RESERVE) if invoked with the 'nonblocking' argument set
to true.

Signed-off-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: default avatarMatt Fleming <matt@codeblueprint.co.uk>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/1454364428-494-5-git-send-email-matt@codeblueprint.co.uk


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent d3cac1f8

arch/x86/platform/efi/quirks.c

+32 −1
Original line number Diff line number Diff line
@@ -56,6 +56,33 @@ void efi_delete_dummy_variable(void) 
			 0, NULL);

}



/*

 * In the nonblocking case we do not attempt to perform garbage

 * collection if we do not have enough free space. Rather, we do the

 * bare minimum check and give up immediately if the available space

 * is below EFI_MIN_RESERVE.

 *

 * This function is intended to be small and simple because it is

 * invoked from crash handler paths.

 */

static efi_status_t

query_variable_store_nonblocking(u32 attributes, unsigned long size)

{

	efi_status_t status;

	u64 storage_size, remaining_size, max_size;



	status = efi.query_variable_info_nonblocking(attributes, &storage_size,

						     &remaining_size,

						     &max_size);

	if (status != EFI_SUCCESS)

		return status;



	if (remaining_size - size < EFI_MIN_RESERVE)

		return EFI_OUT_OF_RESOURCES;



	return EFI_SUCCESS;

}



/*

 * Some firmware implementations refuse to boot if there's insufficient space

 * in the variable store. Ensure that we never use more than a safe limit.
@@ -63,7 +90,8 @@ void efi_delete_dummy_variable(void) 
 * Return EFI_SUCCESS if it is safe to write 'size' bytes to the variable

 * store.

 */

efi_status_t efi_query_variable_store(u32 attributes, unsigned long size)

efi_status_t efi_query_variable_store(u32 attributes, unsigned long size,

				      bool nonblocking)

{

	efi_status_t status;

	u64 storage_size, remaining_size, max_size;
@@ -71,6 +99,9 @@ efi_status_t efi_query_variable_store(u32 attributes, unsigned long size) 
	if (!(attributes & EFI_VARIABLE_NON_VOLATILE))

		return 0;



	if (nonblocking)

		return query_variable_store_nonblocking(attributes, size);



	status = efi.query_variable_info(attributes, &storage_size,

					 &remaining_size, &max_size);

	if (status != EFI_SUCCESS)

drivers/firmware/efi/vars.c

+14 −2
Original line number Diff line number Diff line
@@ -234,7 +234,18 @@ check_var_size(u32 attributes, unsigned long size) 
	if (!fops->query_variable_store)

		return EFI_UNSUPPORTED;



	return fops->query_variable_store(attributes, size);

	return fops->query_variable_store(attributes, size, false);

}



static efi_status_t

check_var_size_nonblocking(u32 attributes, unsigned long size)

{

	const struct efivar_operations *fops = __efivars->ops;



	if (!fops->query_variable_store)

		return EFI_UNSUPPORTED;



	return fops->query_variable_store(attributes, size, true);

}



static int efi_status_to_err(efi_status_t status)
@@ -615,7 +626,8 @@ efivar_entry_set_nonblocking(efi_char16_t *name, efi_guid_t vendor, 
	if (!spin_trylock_irqsave(&__efivars->lock, flags))

		return -EBUSY;



	status = check_var_size(attributes, size + ucs2_strsize(name, 1024));

	status = check_var_size_nonblocking(attributes,

					    size + ucs2_strsize(name, 1024));

	if (status != EFI_SUCCESS) {

		spin_unlock_irqrestore(&__efivars->lock, flags);

		return -ENOSPC;

include/linux/efi.h

+9 −3
Original line number Diff line number Diff line
@@ -525,7 +525,9 @@ typedef efi_status_t efi_query_capsule_caps_t(efi_capsule_header_t **capsules, 
					      unsigned long count,

					      u64 *max_size,

					      int *reset_type);

typedef efi_status_t efi_query_variable_store_t(u32 attributes, unsigned long size);

typedef efi_status_t efi_query_variable_store_t(u32 attributes,

						unsigned long size,

						bool nonblocking);



void efi_native_runtime_setup(void);
@@ -881,13 +883,17 @@ extern void efi_enter_virtual_mode (void); /* switch EFI to virtual mode, if pos 
#ifdef CONFIG_X86

extern void efi_late_init(void);

extern void efi_free_boot_services(void);

extern efi_status_t efi_query_variable_store(u32 attributes, unsigned long size);

extern efi_status_t efi_query_variable_store(u32 attributes,

					     unsigned long size,

					     bool nonblocking);

extern void efi_find_mirror(void);

#else

static inline void efi_late_init(void) {}

static inline void efi_free_boot_services(void) {}



static inline efi_status_t efi_query_variable_store(u32 attributes, unsigned long size)

static inline efi_status_t efi_query_variable_store(u32 attributes,

						    unsigned long size,

						    bool nonblocking)

{

	return EFI_SUCCESS;

}