x86/platform/UV: Fix bug with iounmap() of the UV4 EFI System Table causing a crash

Orabug: 25477822

Save the uv_systab::size field before doing the iounmap()
of the struct pointer, to avoid a NULL dereference crash.

Tested-by: Frank Ramsay <framsay@sgi.com>
Tested-by: John Estabrook <estabrook@sgi.com>
Signed-off-by: Mike Travis <travis@sgi.com>
Reviewed-by: Dimitri Sivanich <sivanich@sgi.com>
Reviewed-by: Nathan Zimmer <nzimmer@sgi.com>
Cc: Alex Thorlton <athorlton@sgi.com>
Cc: Andrew Banman <abanman@sgi.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russ Anderson <rja@sgi.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160801184050.250424783@asylum.americas.sgi.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
(cherry picked from commit e363d24c2b997c421476c6aa00547edadf678efe)
Signed-off-by: Brian Maly <brian.maly@oracle.com>

diff --git a/arch/x86/platform/uv/bios_uv.c b/arch/x86/platform/uv/bios_uv.c
index 815fec6e05e2b8801f83c0aa34baef9aeeeb27ef..ccd26032c2e2c4634382c6769d37cd5a7ef4ec5a 100644 (file)
--- a/arch/x86/platform/uv/bios_uv.c
+++ b/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;
                }
        }