From 1f4eb9d27d0ebd62a0b6cdff8213726f5ae8f25c Mon Sep 17 00:00:00 2001 From: Ross Lagerwall Date: Tue, 10 Mar 2015 13:52:01 +0100 Subject: [PATCH] EFI: fix getting EFI variable list on some systems Copy the entire output buffer to the guest because some firmwares update size on successful calls (contrary to the spec) and the buffer may contain data beyond the output size that the firmware requires on a subsequent GetNextVariableName() call (e.g. a NULL character). Note that this shouldn't change the amount of data copied because on success, a compliant firmware does not change size and so the entire buffer is copied anyway. If size is changed, Xen does not copy the buffer. Without this change, the following (simplified) sequence would occur: GetNextVariableName: in \0, size 1024 || out AdminPw\0, size 7 GetNextVariableName: in AdminPw\0, size 1024 || out UserPw\0, size 6 GetNextVariableName: in UserPww\0, size 1024 || NOT FOUND This was seen on an Intel S1200RP_SE with firmware S1200RP.86B.02.02.0005.102320140911, version 4.6, date 2014-10-23. Signed-off-by: Ross Lagerwall Reviewed-by: Andrew Cooper --- xen/common/efi/runtime.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/xen/common/efi/runtime.c b/xen/common/efi/runtime.c index 7ed5bfabd4..5ed8b01025 100644 --- a/xen/common/efi/runtime.c +++ b/xen/common/efi/runtime.c @@ -516,9 +516,13 @@ int efi_runtime_call(struct xenpf_efi_runtime_call *op) cast_guid(&op->u.get_next_variable_name.vendor_guid)); efi_rs_leave(cr3); + /* + * Copy the variable name if necessary. The caller provided size + * is used because some firmwares update size when they shouldn't. + * */ if ( !EFI_ERROR(status) && - copy_to_guest(op->u.get_next_variable_name.name, - name.raw, size) ) + __copy_to_guest(op->u.get_next_variable_name.name, + name.raw, op->u.get_next_variable_name.size) ) rc = -EFAULT; op->u.get_next_variable_name.size = size; } -- 2.39.5