The non-blocking version of efivar_entry_set() gives up directly on
failure to acquire __efivars->lock. However, it also calls check_var_size(),
whose implementation calls the ordinary query_variable_info() and
set_variable() runtime service wrappers, meaning we could still deadlock
if efivar_entry_set_nonblocking() is called from an atomic context that
interrupted a runtime service already in progress on the same CPU.
So drop the call to check_var_size(). This is potentially unsafe on some
UEFI implementations that fail to boot if the varstore fills up, but
those systems are unlikely to be using efi-pstore in the first place.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
---
drivers/firmware/efi/vars.c | 12 +++---------
1 file changed, 3 insertions(+), 9 deletions(-)
diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
index 70a0fb10517f..caccdbffc1d0 100644
--- a/drivers/firmware/efi/vars.c
+++ b/drivers/firmware/efi/vars.c
@@ -615,12 +615,6 @@ 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));
- if (status != EFI_SUCCESS) {
- spin_unlock_irqrestore(&__efivars->lock, flags);
- return -ENOSPC;
- }
-
status = ops->set_variable_nonblocking(name, &vendor, attributes,
size, data);
@@ -652,9 +646,6 @@ int efivar_entry_set_safe(efi_char16_t *name, efi_guid_t vendor, u32 attributes,
unsigned long flags;
efi_status_t status;
- if (!ops->query_variable_store)
- return -ENOSYS;
-
/*
* If the EFI variable backend provides a non-blocking
* ->set_variable() operation and we're in a context where we
@@ -669,6 +660,9 @@ int efivar_entry_set_safe(efi_char16_t *name, efi_guid_t vendor, u32 attributes,
return efivar_entry_set_nonblocking(name, vendor, attributes,
size, data);
+ if (!ops->query_variable_store)
+ return -ENOSYS;
+
if (!block) {
if (!spin_trylock_irqsave(&__efivars->lock, flags))
return -EBUSY;
--
1.9.1
--
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