efivars: Respect "block" flag in efivar_entry_set_safe()

When the "block" flag is false, the old code would sometimes still call
check_var_size(), which wrongly tells ->query_variable_store() that it can
block.

As far as I can tell, this can't really materialize as a bug at the moment,
because ->query_variable_store only does something on X86 with generic EFI,
and in that configuration we always take the efivar_entry_set_nonblocking()
path.

Fixes: ca0e30dcaa53 ("efi: Add nonblocking option to efi_query_variable_store()")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20220218180559.1432559-1-jannh@google.com

diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
index abdc8a6a396318a915455dd73e26439b88c1b003..cae590bd08f27c3c769459802d3546d1542c2ff8 100644 (file)
--- a/drivers/firmware/efi/vars.c
+++ b/drivers/firmware/efi/vars.c
@@ -742,6 +742,7 @@ int efivar_entry_set_safe(efi_char16_t *name, efi_guid_t vendor, u32 attributes,
 {
        const struct efivar_operations *ops;
        efi_status_t status;
+       unsigned long varsize;
 
        if (!__efivars)
                return -EINVAL;
@@ -764,15 +765,17 @@ 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);
 
+       varsize = size + ucs2_strsize(name, 1024);
        if (!block) {
                if (down_trylock(&efivars_lock))
                        return -EBUSY;
+               status = check_var_size_nonblocking(attributes, varsize);
        } else {
                if (down_interruptible(&efivars_lock))
                        return -EINTR;
+               status = check_var_size(attributes, varsize);
        }
 
-       status = check_var_size(attributes, size + ucs2_strsize(name, 1024));
        if (status != EFI_SUCCESS) {
                up(&efivars_lock);
                return -ENOSPC;