The following commit has been merged into the x86/fpu branch of tip:
Commit-ID: 6f9866a166cd1ad3ebb2dcdb3874aa8fee8dea2f
Gitweb: https://git.kernel.org/tip/6f9866a166cd1ad3ebb2dcdb3874aa8fee8dea2f
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Wed, 23 Jun 2021 14:02:32 +02:00
Committer: Borislav Petkov <bp@xxxxxxx>
CommitterDate: Wed, 23 Jun 2021 23:45:31 +02:00
x86/fpu/signal: Let xrstor handle the features to init
There is no reason to do an extra XRSTOR from init_fpstate for feature
bits which have been cleared by user space in the FX magic xfeatures
storage.
Just clear them in the task's XSTATE header and do a full restore which
will put these cleared features into init state.
There is no real difference in performance because the current code
already does a full restore when the xfeatures bits are preserved as the
signal frame setup has stored them, which is the full UABI feature set.
[ bp: Use the negated mxcsr_feature_mask in the MXCSR check. ]
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Reviewed-by: Borislav Petkov <bp@xxxxxxx>
Link: https://lkml.kernel.org/r/20210623121457.804115017@xxxxxxxxxxxxx
---
arch/x86/kernel/fpu/signal.c | 89 ++++++++++++-----------------------
1 file changed, 31 insertions(+), 58 deletions(-)
diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 4c252d0..445c57c 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -220,36 +220,6 @@ retry:
return 0;
}
-static inline void
-sanitize_restored_user_xstate(union fpregs_state *state,
- struct user_i387_ia32_struct *ia32_env, u64 mask)
-{
- struct xregs_state *xsave = &state->xsave;
- struct xstate_header *header = &xsave->header;
-
- if (use_xsave()) {
- /*
- * Clear all feature bits which are not set in mask.
- *
- * Supervisor state has to be preserved. The sigframe
- * restore can only modify user features, i.e. @mask
- * cannot contain them.
- */
- header->xfeatures &= mask | xfeatures_mask_supervisor();
- }
-
- if (use_fxsr()) {
- /*
- * mscsr reserved bits must be masked to zero for security
- * reasons.
- */
- xsave->i387.mxcsr &= mxcsr_feature_mask;
-
- if (ia32_env)
- convert_to_fxsr(&state->fxsave, ia32_env);
- }
-}
-
static int __restore_fpregs_from_user(void __user *buf, u64 xrestore,
bool fx_only)
{
@@ -352,6 +322,8 @@ static int __fpu_restore_sig(void __user *buf, void __user *buf_fx,
fx_only = !fx_sw_user.magic1;
state_size = fx_sw_user.xstate_size;
user_xfeatures = fx_sw_user.xfeatures;
+ } else {
+ user_xfeatures = XFEATURE_MASK_FPSSE;
}
if (likely(!ia32_fxstate)) {
@@ -395,54 +367,55 @@ static int __fpu_restore_sig(void __user *buf, void __user *buf_fx,
set_thread_flag(TIF_NEED_FPU_LOAD);
}
__fpu_invalidate_fpregs_state(fpu);
+ __cpu_invalidate_fpregs_state();
fpregs_unlock();
if (use_xsave() && !fx_only) {
- u64 init_bv = xfeatures_mask_uabi() & ~user_xfeatures;
-
ret = copy_sigframe_from_user_to_xstate(&fpu->state.xsave, buf_fx);
if (ret)
return ret;
+ } else {
+ if (__copy_from_user(&fpu->state.fxsave, buf_fx,
+ sizeof(fpu->state.fxsave)))
+ return -EFAULT;
- sanitize_restored_user_xstate(&fpu->state, &env, user_xfeatures);
+ /* Reject invalid MXCSR values. */
+ if (fpu->state.fxsave.mxcsr & ~mxcsr_feature_mask)
+ return -EINVAL;
- fpregs_lock();
- if (unlikely(init_bv))
- os_xrstor(&init_fpstate.xsave, init_bv);
+ /* Enforce XFEATURE_MASK_FPSSE when XSAVE is enabled */
+ if (use_xsave())
+ fpu->state.xsave.header.xfeatures |= XFEATURE_MASK_FPSSE;
+ }
+
+ /* Fold the legacy FP storage */
+ convert_to_fxsr(&fpu->state.fxsave, &env);
+ fpregs_lock();
+ if (use_xsave()) {
/*
- * Restore previously saved supervisor xstates along with
- * copied-in user xstates.
+ * Remove all UABI feature bits not set in user_xfeatures
+ * from the memory xstate header which makes the full
+ * restore below bring them into init state. This works for
+ * fx_only mode as well because that has only FP and SSE
+ * set in user_xfeatures.
+ *
+ * Preserve supervisor states!
*/
- ret = os_xrstor_safe(&fpu->state.xsave,
- user_xfeatures | xfeatures_mask_supervisor());
+ u64 mask = user_xfeatures | xfeatures_mask_supervisor();
+ fpu->state.xsave.header.xfeatures &= mask;
+ ret = os_xrstor_safe(&fpu->state.xsave, xfeatures_mask_all);
} else {
- ret = __copy_from_user(&fpu->state.fxsave, buf_fx, state_size);
- if (ret)
- return -EFAULT;
-
- sanitize_restored_user_xstate(&fpu->state, &env, user_xfeatures);
-
- fpregs_lock();
- if (use_xsave()) {
- u64 init_bv;
-
- init_bv = xfeatures_mask_uabi() & ~XFEATURE_MASK_FPSSE;
- os_xrstor(&init_fpstate.xsave, init_bv);
- }
-
ret = fxrstor_safe(&fpu->state.fxsave);
}
- if (!ret)
+ if (likely(!ret))
fpregs_mark_activate();
- else
- fpregs_deactivate(fpu);
+
fpregs_unlock();
return ret;
}
-
static inline int xstate_sigframe_size(void)
{
return use_xsave() ? fpu_user_xstate_size + FP_XSTATE_MAGIC2_SIZE :
|