Commit-ID: dffba9a31c7769be3231c420d4b364c92ba3f1ac
Gitweb: http://git.kernel.org/tip/dffba9a31c7769be3231c420d4b364c92ba3f1ac
Author: Yu-cheng Yu <[email protected]>
AuthorDate: Mon, 23 Jan 2017 14:54:44 -0800
Committer: Ingo Molnar <[email protected]>
CommitDate: Tue, 24 Jan 2017 09:04:48 +0100
x86/fpu/xstate: Fix xcomp_bv in XSAVES header
The compacted-format XSAVES area is determined at boot time and
never changed after. The field xsave.header.xcomp_bv indicates
which components are in the fixed XSAVES format.
In fpstate_init() we did not set xcomp_bv to reflect the XSAVES
format since at the time there is no valid data.
However, after we do copy_init_fpstate_to_fpregs() in fpu__clear(),
as in commit:
b22cbe404a9c x86/fpu: Fix invalid FPU ptrace state after execve()
and when __fpu_restore_sig() does fpu__restore() for a COMPAT-mode
app, a #GP occurs. This can be easily triggered by doing valgrind on
a COMPAT-mode "Hello World," as reported by Joakim Tjernlund and
others:
https://bugzilla.kernel.org/show_bug.cgi?id=190061
Fix it by setting xcomp_bv correctly.
This patch also moves the xcomp_bv initialization to the proper
place, which was in copyin_to_xsaves() as of:
4c833368f0bf x86/fpu: Set the xcomp_bv when we fake up a XSAVES area
which fixed the bug too, but it's more efficient and cleaner to
initialize things once per boot, not for every signal handling
operation.
Reported-by: Kevin Hao <[email protected]>
Reported-by: Joakim Tjernlund <[email protected]>
Signed-off-by: Yu-cheng Yu <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Fenghua Yu <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Ravi V. Shankar <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Link:
http://lkml.kernel.org/r/[email protected]
[ Combined it with 4c833368f0bf. ]
Signed-off-by: Ingo Molnar <[email protected]>
---
arch/x86/kernel/fpu/core.c | 4 +++-
arch/x86/kernel/fpu/xstate.c | 1 -
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index e4e97a5..de72344 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -9,6 +9,7 @@
#include <asm/fpu/regset.h>
#include <asm/fpu/signal.h>
#include <asm/fpu/types.h>
+#include <asm/fpu/xstate.h>
#include <asm/traps.h>
#include <linux/hardirq.h>
@@ -183,7 +184,8 @@ void fpstate_init(union fpregs_state *state)
* it will #GP. Make sure it is replaced after the memset().
*/
if (static_cpu_has(X86_FEATURE_XSAVES))
- state->xsave.header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT;
+ state->xsave.header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT |
+ xfeatures_mask;
if (static_cpu_has(X86_FEATURE_FXSR))
fpstate_init_fxstate(&state->fxsave);
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index e287b90..1d77704 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -1070,7 +1070,6 @@ int copyin_to_xsaves(const void *kbuf, const void __user
*ubuf,
* Add back in the features that came in from userspace:
*/
xsave->header.xfeatures |= xfeatures;
- xsave->header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT |
xsave->header.xfeatures;
return 0;
}
