From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: linux-kernel@vger.kernel.org
Cc: x86@kernel.org, "Andy Lutomirski" <luto@kernel.org>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
kvm@vger.kernel.org, "Jason A. Donenfeld" <Jason@zx2c4.com>,
"Rik van Riel" <riel@surriel.com>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
"Sebastian Andrzej Siewior" <bigeasy@linutronix.de>
Subject: [PATCH 22/23] x86/fpu: Don't restore the FPU state directly from userland in __fpu__restore_sig()
Date: Wed, 7 Nov 2018 20:48:57 +0100 [thread overview]
Message-ID: <20181107194858.9380-23-bigeasy@linutronix.de> (raw)
In-Reply-To: <20181107194858.9380-1-bigeasy@linutronix.de>
__fpu__restore_sig() restores the CPU's FPU state directly from
userland. If we restore registers on return to userland then we can't
load them directly from userland because a context switch/BH could
destroy them.
Restore the FPU registers after they have been copied from userland.
__fpregs_changes_begin() ensures that they are not modified while beeing
worked on. TIF_NEED_FPU_LOAD is clreared we want to keep our state, not
the saved state.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
arch/x86/include/asm/fpu/internal.h | 34 -----------------------------
arch/x86/kernel/fpu/signal.c | 33 ++++++++++++++++++----------
2 files changed, 22 insertions(+), 45 deletions(-)
diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 9e213a6703c84..5e86ff60a3a5c 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -137,28 +137,11 @@ static inline void copy_kernel_to_fxregs(struct fxregs_state *fx)
}
}
-static inline int copy_user_to_fxregs(struct fxregs_state __user *fx)
-{
- if (IS_ENABLED(CONFIG_X86_32))
- return user_insn(fxrstor %[fx], "=m" (*fx), [fx] "m" (*fx));
- else if (IS_ENABLED(CONFIG_AS_FXSAVEQ))
- return user_insn(fxrstorq %[fx], "=m" (*fx), [fx] "m" (*fx));
-
- /* See comment in copy_fxregs_to_kernel() below. */
- return user_insn(rex64/fxrstor (%[fx]), "=m" (*fx), [fx] "R" (fx),
- "m" (*fx));
-}
-
static inline void copy_kernel_to_fregs(struct fregs_state *fx)
{
kernel_insn(frstor %[fx], "=m" (*fx), [fx] "m" (*fx));
}
-static inline int copy_user_to_fregs(struct fregs_state __user *fx)
-{
- return user_insn(frstor %[fx], "=m" (*fx), [fx] "m" (*fx));
-}
-
static inline void copy_fxregs_to_kernel(struct fpu *fpu)
{
if (IS_ENABLED(CONFIG_X86_32))
@@ -333,23 +316,6 @@ static inline void copy_kernel_to_xregs(struct xregs_state *xstate, u64 mask)
XSTATE_XRESTORE(xstate, lmask, hmask);
}
-/*
- * Restore xstate from user space xsave area.
- */
-static inline int copy_user_to_xregs(struct xregs_state __user *buf, u64 mask)
-{
- struct xregs_state *xstate = ((__force struct xregs_state *)buf);
- u32 lmask = mask;
- u32 hmask = mask >> 32;
- int err;
-
- stac();
- XSTATE_OP(XRSTOR, xstate, lmask, hmask, err);
- clac();
-
- return err;
-}
-
/*
* These must be called with preempt disabled. Returns
* 'true' if the FPU state is still intact and we can
diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 179e2b19976ad..9720529859483 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -228,23 +228,30 @@ sanitize_restored_xstate(union fpregs_state *state,
/*
* Restore the extended state if present. Otherwise, restore the FP/SSE state.
*/
-static inline int copy_user_to_fpregs_zeroing(void __user *buf, u64 xbv, int fx_only)
+static void copy_to_fpregs_zeroing(struct fpu *fpu, u64 xbv, int fx_only)
{
+ __fpregs_changes_begin();
if (use_xsave()) {
- if ((unsigned long)buf % 64 || fx_only) {
+ if (fx_only) {
u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE;
+
copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
- return copy_user_to_fxregs(buf);
+ copy_kernel_to_fxregs(&fpu->state.fxsave);
} else {
u64 init_bv = xfeatures_mask & ~xbv;
+
if (unlikely(init_bv))
copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
- return copy_user_to_xregs(buf, xbv);
+ copy_kernel_to_xregs(&fpu->state.xsave, xbv);
}
} else if (use_fxsr()) {
- return copy_user_to_fxregs(buf);
- } else
- return copy_user_to_fregs(buf);
+ copy_kernel_to_fxregs(&fpu->state.fxsave);
+ } else {
+ copy_kernel_to_fregs(&fpu->state.fsave);
+ }
+ clear_thread_flag(TIF_NEED_FPU_LOAD);
+ fpregs_activate(fpu);
+ __fpregs_changes_end();
}
static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
@@ -255,6 +262,7 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
int state_size = fpu_kernel_xstate_size;
u64 xfeatures = 0;
int fx_only = 0;
+ int err = 0;
ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
IS_ENABLED(CONFIG_IA32_EMULATION));
@@ -298,7 +306,6 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
union fpregs_state *state;
void *tmp;
struct user_i387_ia32_struct env;
- int err = 0;
tmp = kmalloc(sizeof(*state) + fpu_kernel_xstate_size + 64, GFP_KERNEL);
if (!tmp)
@@ -327,12 +334,16 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
} else {
/*
* For 64-bit frames and 32-bit fsave frames, restore the user
- * state to the registers directly (with exceptions handled).
+ * state from a copy in thread's fpu state.
*/
- if (copy_user_to_fpregs_zeroing(buf_fx, xfeatures, fx_only)) {
+ err = __copy_from_user(&fpu->state.xsave, buf_fx, state_size);
+ if (err) {
fpu__clear(fpu);
- return -1;
+ return -EFAULT;
}
+ if ((unsigned long)buf_fx % 64)
+ fx_only = 1;
+ copy_to_fpregs_zeroing(fpu, xfeatures, fx_only);
}
return 0;
--
2.19.1
next prev parent reply other threads:[~2018-11-07 19:49 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-07 19:48 [PATCH v4] x86: load FPU registers on return to userland Sebastian Andrzej Siewior
2018-11-07 19:48 ` [PATCH 01/23] x86/fpu: Use ULL for shift in xfeature_uncompacted_offset() Sebastian Andrzej Siewior
2018-11-08 11:38 ` Borislav Petkov
2018-11-09 16:56 ` Sebastian Andrzej Siewior
2018-11-07 19:48 ` [PATCH 02/23] x86/fpu: Remove fpu->initialized usage in __fpu__restore_sig() Sebastian Andrzej Siewior
2018-11-08 14:57 ` Borislav Petkov
2018-11-09 17:35 ` Sebastian Andrzej Siewior
2018-11-09 18:52 ` Borislav Petkov
2018-11-09 23:25 ` Sebastian Andrzej Siewior
2018-11-12 15:56 ` [PATCH] x86/fpu: Disable BH while while loading FPU registers " Sebastian Andrzej Siewior
2018-11-12 17:48 ` Dave Hansen
2018-11-19 11:41 ` Sebastian Andrzej Siewior
2018-11-19 15:04 ` Dave Hansen
2018-11-19 15:06 ` Sebastian Andrzej Siewior
2018-11-19 15:08 ` Dave Hansen
2018-11-19 15:19 ` Sebastian Andrzej Siewior
2018-11-07 19:48 ` [PATCH 03/23] x86/fpu: Remove fpu__restore() Sebastian Andrzej Siewior
2018-11-07 19:48 ` [PATCH 04/23] x86/entry/32: Remove asm/math_emu.h include Sebastian Andrzej Siewior
2018-11-08 18:45 ` Andy Lutomirski
2018-11-07 19:48 ` [PATCH 05/23] x86/fpu: Remove preempt_disable() in fpu__clear() Sebastian Andrzej Siewior
2018-11-07 19:48 ` [PATCH 06/23] x86/fpu: Always init the `state' " Sebastian Andrzej Siewior
2018-11-07 19:48 ` [PATCH 07/23] x86/fpu: Remove fpu->initialized usage in copy_fpstate_to_sigframe() Sebastian Andrzej Siewior
2018-11-07 19:48 ` [PATCH 08/23] x86/fpu: Remove fpu->initialized Sebastian Andrzej Siewior
2018-11-07 19:48 ` [PATCH 09/23] x86/fpu: Remove user_fpu_begin() Sebastian Andrzej Siewior
2018-11-07 19:48 ` [PATCH 10/23] x86/entry: Remove _TIF_ALLWORK_MASK Sebastian Andrzej Siewior
2018-11-07 19:48 ` [PATCH 11/23] x86/fpu: Add (__)make_fpregs_active helpers Sebastian Andrzej Siewior
2018-11-07 19:48 ` [PATCH 12/23] x86/fpu: Make __raw_xsave_addr() use feature number instead of mask Sebastian Andrzej Siewior
2018-11-07 19:48 ` [PATCH 13/23] x86/fpu: Make get_xsave_field_ptr() and get_xsave_addr() " Sebastian Andrzej Siewior
2018-11-07 19:48 ` [PATCH 14/23] x86/pkeys: Make init_pkru_value static Sebastian Andrzej Siewior
2018-11-07 19:48 ` [PATCH 15/23] x86/fpu: Only write PKRU if it is different from current Sebastian Andrzej Siewior
2018-11-07 19:48 ` [PATCH 16/23] x86/pkeys: Don't check if PKRU is zero before writting it Sebastian Andrzej Siewior
2018-11-07 19:48 ` [PATCH 17/23] x86/fpu: Eager switch PKRU state Sebastian Andrzej Siewior
2018-11-08 11:12 ` Paolo Bonzini
2018-11-19 18:17 ` Sebastian Andrzej Siewior
2018-11-07 19:48 ` [PATCH 18/23] x86/entry: Add TIF_NEED_FPU_LOAD Sebastian Andrzej Siewior
2018-11-07 19:48 ` [PATCH 19/23] x86/fpu: Always store the registers in copy_fpstate_to_sigframe() Sebastian Andrzej Siewior
2018-11-07 19:48 ` [PATCH 20/23] x86/fpu: Prepare copy_fpstate_to_sigframe() for TIF_NEED_FPU_LOAD Sebastian Andrzej Siewior
2018-11-07 19:48 ` [PATCH 21/23] x86/fpu: Update xstate's PKRU value on write_pkru() Sebastian Andrzej Siewior
2018-11-07 19:48 ` Sebastian Andrzej Siewior [this message]
2018-11-08 18:25 ` [PATCH 22/23] x86/fpu: Don't restore the FPU state directly from userland in __fpu__restore_sig() Andy Lutomirski
2018-11-09 19:09 ` Sebastian Andrzej Siewior
2018-11-07 19:48 ` [PATCH 23/23] x86/fpu: Defer FPU state load until return to userspace Sebastian Andrzej Siewior
2018-11-08 8:33 ` Sebastian Andrzej Siewior
2018-11-12 3:02 ` [PATCH v4] x86: load FPU registers on return to userland Wanpeng Li
2018-11-12 3:26 ` Jason A. Donenfeld
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