efi: fix panic in kdump kernel

[ Upstream commit 62b71cd73d41ddac6b1760402bbe8c4932e23531 ]

Check if get_next_variable() is actually valid pointer before
calling it. In kdump kernel this method is set to NULL that causes
panic during the kexec-ed kernel boot.

Tested with QEMU and OVMF firmware.

Fixes: bad267f9e18f ("efi: verify that variable services are supported")
Signed-off-by: Oleksandr Tymoshenko <ovt@google.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 1974f0ad32badbea55d1f4c1a43f4f95c065c3b5..2c1095dcc2f2f82e4d5a5515372246cdf1a5bab9 100644 (file)
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -199,6 +199,8 @@ static bool generic_ops_supported(void)
 
        name_size = sizeof(name);
 
+       if (!efi.get_next_variable)
+               return false;
        status = efi.get_next_variable(&name_size, &name, &guid);
        if (status == EFI_UNSUPPORTED)
                return false;