[PATCH 5.4 40/64] efivars: Respect "block" flag in efivar_entry_set_safe()

Greg Kroah-Hartman
2022-03-07T09:41:10Z

From: Jann Horn <jannh@google.com>

commit 258dd902022cb10c83671176688074879517fd21 upstream.

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
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/firmware/efi/vars.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/firmware/efi/vars.c
+++ b/drivers/firmware/efi/vars.c
@@ -750,6 +750,7 @@ int efivar_entry_set_safe(efi_char16_t *
{
const struct efivar_operations *ops;
efi_status_t status;
+ unsigned long varsize;

if (!__efivars)
return -EINVAL;
@@ -772,15 +773,17 @@ int efivar_entry_set_safe(efi_char16_t *
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;