[PATCH 2/4] x86/platform/UV: Fix problem with iounmap UV4 EFI System Table causing panic

[Mike Travis]

Save the size field from the uv_systab struct before doing the iounmap
of the struct pointer, to avoid a null dereference error.

Reviewed-by: Dimitri Sivanich <sivanich@xxxxxxx>
Reviewed-by: Nathan Zimmer <nzimmer@xxxxxxx>
Tested-by: Frank Ramsay <framsay@xxxxxxx>
Tested-by: John Estabrook <estabrook@xxxxxxx>
Signed-off-by: Mike Travis <travis@xxxxxxx>
---
v2: modify description and changelog.
---
 arch/x86/platform/uv/bios_uv.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- linux.orig/arch/x86/platform/uv/bios_uv.c
+++ linux/arch/x86/platform/uv/bios_uv.c
@@ -200,12 +200,14 @@ void uv_bios_init(void)
 		return;
 	}
 
+	/* Starting with UV4 the UV systab size is variable */
 	if (uv_systab->revision >= UV_SYSTAB_VERSION_UV4) {
+		int size = uv_systab->size;
+
 		iounmap(uv_systab);
-		uv_systab = ioremap(efi.uv_systab, uv_systab->size);
+		uv_systab = ioremap(efi.uv_systab, size);
 		if (!uv_systab) {
-			pr_err("UV: UVsystab: ioremap(%d) failed!\n",
-				uv_systab->size);
+			pr_err("UV: UVsystab: ioremap(%d) failed!\n", size);
 			return;
 		}
 	}

--