From a8424003679e90b9952e20adcd1ff1560d9dd3e9 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Thu, 11 Jun 2015 12:34:00 -0700 Subject: [PATCH] x86/fpu: Fix double-increment in setup_xstate_features() I noticed that my MPX tracepoints were producing garbage for the lower and upper bounds: mpx_bounds_register_exception: address referenced: 0x00007fffffffccb7 bounds: lower: 0x0 ~upper: 0xffffffffffffffff mpx_bounds_register_exception: address referenced: 0x00007fffffffccbf bounds: lower: 0x0 ~upper: 0xffffffffffffffff This is, of course, bogus because 0x00007fffffffccbf is *within* the bounds. I assumed that my instruction decoder was bad and went looking at it. But I eventually realized that I was getting a '0' offset back from xstate_offsets[BNDREGS]. It was being skipped in the initialization, which is obviously bogus, so remove the extra leaf++. This also goes an initializes xstate_offsets/sizes[] to -1 so so that bugs like this will oops instead of silently failing in interesting ways. This was introduced by: 39f1acd ("x86/fpu/xstate: Don't assume the first zero xfeatures zero bit means the end") Signed-off-by: Dave Hansen Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: dave@sr71.net Link: http://lkml.kernel.org/r/20150611193400.2E0B00DB@viggo.jf.intel.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/fpu/xstate.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index 49d0d9b2a60a..62fc001c7846 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -31,7 +31,8 @@ static const char *xfeature_names[] = */ u64 xfeatures_mask __read_mostly; -static unsigned int xstate_offsets[XFEATURES_NR_MAX], xstate_sizes[XFEATURES_NR_MAX]; +static unsigned int xstate_offsets[XFEATURES_NR_MAX] = { [ 0 ... XFEATURES_NR_MAX - 1] = -1}; +static unsigned int xstate_sizes[XFEATURES_NR_MAX] = { [ 0 ... XFEATURES_NR_MAX - 1] = -1}; static unsigned int xstate_comp_offsets[sizeof(xfeatures_mask)*8]; /* The number of supported xfeatures in xfeatures_mask: */ @@ -187,7 +188,6 @@ static void __init setup_xstate_features(void) xstate_sizes[leaf] = eax; printk(KERN_INFO "x86/fpu: xstate_offset[%d]: %04x, xstate_sizes[%d]: %04x\n", leaf, ebx, leaf, eax); - leaf++; } } -- 2.20.1