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Message-Id: <20200512145444.15483-7-yu-cheng.yu@intel.com>
Date: Tue, 12 May 2020 07:54:40 -0700
From: Yu-cheng Yu <yu-cheng.yu@...el.com>
To: linux-kernel@...r.kernel.org, x86@...nel.org,
"H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Tony Luck <tony.luck@...el.com>,
Andy Lutomirski <luto@...nel.org>,
Borislav Petkov <bp@...en8.de>,
Rik van Riel <riel@...riel.com>,
"Ravi V. Shankar" <ravi.v.shankar@...el.com>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Fenghua Yu <fenghua.yu@...el.com>,
Peter Zijlstra <peterz@...radead.org>
Cc: Yu-cheng Yu <yu-cheng.yu@...el.com>
Subject: [PATCH v4 06/10] x86/fpu/xstate: Update sanitize_restored_xstate() for supervisor xstates
The function sanitize_restored_xstate() sanitizes user xstates of an XSAVE
buffer by clearing bits not in the input 'xfeatures' from the buffer's
header->xfeatures, effectively resetting those features back to the init
state.
When supervisor xstates are introduced, it is necessary to make sure only
user xstates are sanitized. Ensure supervisor bits in header->xfeatures
stay set and supervisor states are not modified.
To make names clear, also:
- Rename the function to sanitize_restored_user_xstate().
- Rename input parameter 'xfeatures' to 'user_xfeatures'.
- In __fpu__restore_sig(), rename 'xfeatures' to 'user_xfeatures'.
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@...el.com>
Reviewed-by: Dave Hansen <dave.hansen@...ux.intel.com>
---
v3:
- Change xfeatures_user to user_xfeatures.
arch/x86/kernel/fpu/signal.c | 37 +++++++++++++++++++++++-------------
1 file changed, 24 insertions(+), 13 deletions(-)
diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index cd6eafba12da..40583487883e 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -211,9 +211,9 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
}
static inline void
-sanitize_restored_xstate(union fpregs_state *state,
- struct user_i387_ia32_struct *ia32_env,
- u64 xfeatures, int fx_only)
+sanitize_restored_user_xstate(union fpregs_state *state,
+ struct user_i387_ia32_struct *ia32_env,
+ u64 user_xfeatures, int fx_only)
{
struct xregs_state *xsave = &state->xsave;
struct xstate_header *header = &xsave->header;
@@ -226,13 +226,22 @@ sanitize_restored_xstate(union fpregs_state *state,
*/
/*
- * Init the state that is not present in the memory
- * layout and not enabled by the OS.
+ * 'user_xfeatures' might have bits clear which are
+ * set in header->xfeatures. This represents features that
+ * were in init state prior to a signal delivery, and need
+ * to be reset back to the init state. Clear any user
+ * feature bits which are set in the kernel buffer to get
+ * them back to the init state.
+ *
+ * Supervisor state is unchanged by input from userspace.
+ * Ensure supervisor state bits stay set and supervisor
+ * state is not modified.
*/
if (fx_only)
header->xfeatures = XFEATURE_MASK_FPSSE;
else
- header->xfeatures &= xfeatures;
+ header->xfeatures &= user_xfeatures |
+ xfeatures_mask_supervisor();
}
if (use_fxsr()) {
@@ -281,7 +290,7 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
struct task_struct *tsk = current;
struct fpu *fpu = &tsk->thread.fpu;
struct user_i387_ia32_struct env;
- u64 xfeatures = 0;
+ u64 user_xfeatures = 0;
int fx_only = 0;
int ret = 0;
@@ -314,7 +323,7 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
trace_x86_fpu_xstate_check_failed(fpu);
} else {
state_size = fx_sw_user.xstate_size;
- xfeatures = fx_sw_user.xfeatures;
+ user_xfeatures = fx_sw_user.xfeatures;
}
}
@@ -349,7 +358,7 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
*/
fpregs_lock();
pagefault_disable();
- ret = copy_user_to_fpregs_zeroing(buf_fx, xfeatures, fx_only);
+ ret = copy_user_to_fpregs_zeroing(buf_fx, user_xfeatures, fx_only);
pagefault_enable();
if (!ret) {
fpregs_mark_activate();
@@ -362,7 +371,7 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
if (use_xsave() && !fx_only) {
- u64 init_bv = xfeatures_mask_user() & ~xfeatures;
+ u64 init_bv = xfeatures_mask_user() & ~user_xfeatures;
if (using_compacted_format()) {
ret = copy_user_to_xstate(&fpu->state.xsave, buf_fx);
@@ -375,12 +384,13 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
if (ret)
goto err_out;
- sanitize_restored_xstate(&fpu->state, envp, xfeatures, fx_only);
+ sanitize_restored_user_xstate(&fpu->state, envp, user_xfeatures,
+ fx_only);
fpregs_lock();
if (unlikely(init_bv))
copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
- ret = copy_kernel_to_xregs_err(&fpu->state.xsave, xfeatures);
+ ret = copy_kernel_to_xregs_err(&fpu->state.xsave, user_xfeatures);
} else if (use_fxsr()) {
ret = __copy_from_user(&fpu->state.fxsave, buf_fx, state_size);
@@ -389,7 +399,8 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
goto err_out;
}
- sanitize_restored_xstate(&fpu->state, envp, xfeatures, fx_only);
+ sanitize_restored_user_xstate(&fpu->state, envp,
+ user_xfeatures, fx_only);
fpregs_lock();
if (use_xsave()) {
--
2.21.0
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