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Subject[tip:x86/fpu] x86/fpu: Merge the two code paths in __fpu__restore_sig()
Commit-ID:  c2ff9e9a3d9d6c019394a22989a228d02970a8b1
Gitweb: https://git.kernel.org/tip/c2ff9e9a3d9d6c019394a22989a228d02970a8b1
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
AuthorDate: Wed, 3 Apr 2019 18:41:51 +0200
Committer: Borislav Petkov <bp@suse.de>
CommitDate: Fri, 12 Apr 2019 15:41:25 +0200

x86/fpu: Merge the two code paths in __fpu__restore_sig()

The ia32_fxstate case (32bit with fxsr) and the other (64bit frames or
32bit frames without fxsr) restore both from kernel memory and sanitize
the content.

The !ia32_fxstate version restores missing xstates from "init state"
while the ia32_fxstate doesn't and skips it.

Merge the two code paths and keep the !ia32_fxstate one. Copy only the
user_i387_ia32_struct data structure in the ia32_fxstate.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Dave Hansen <dave.hansen@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: kvm ML <kvm@vger.kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190403164156.19645-23-bigeasy@linutronix.de
---
arch/x86/kernel/fpu/signal.c | 139 +++++++++++++++++--------------------------
1 file changed, 54 insertions(+), 85 deletions(-)

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 9ea1eaa4c9b1..b13e86b29426 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -263,12 +263,17 @@ static inline int copy_user_to_fpregs_zeroing(void __user *buf, u64 xbv, int fx_

static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
{
+ struct user_i387_ia32_struct *envp = NULL;
+ int state_size = fpu_kernel_xstate_size;
int ia32_fxstate = (buf != buf_fx);
struct task_struct *tsk = current;
struct fpu *fpu = &tsk->thread.fpu;
- int state_size = fpu_kernel_xstate_size;
+ struct user_i387_ia32_struct env;
+ union fpregs_state *state;
u64 xfeatures = 0;
int fx_only = 0;
+ int ret = 0;
+ void *tmp;

ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
IS_ENABLED(CONFIG_IA32_EMULATION));
@@ -303,105 +308,69 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
}
}

+ tmp = kzalloc(sizeof(*state) + fpu_kernel_xstate_size + 64, GFP_KERNEL);
+ if (!tmp)
+ return -ENOMEM;
+ state = PTR_ALIGN(tmp, 64);
+
+ if ((unsigned long)buf_fx % 64)
+ fx_only = 1;
+
+ /*
+ * For 32-bit frames with fxstate, copy the fxstate so it can be
+ * reconstructed later.
+ */
if (ia32_fxstate) {
- /*
- * For 32-bit frames with fxstate, copy the user state to the
- * thread's fpu state, reconstruct fxstate from the fsave
- * header. Validate and sanitize the copied state.
- */
- struct user_i387_ia32_struct env;
- union fpregs_state *state;
- int err = 0;
- void *tmp;
+ ret = __copy_from_user(&env, buf, sizeof(env));
+ if (ret)
+ goto err_out;
+ envp = &env;
+ }

- tmp = kzalloc(sizeof(*state) + fpu_kernel_xstate_size + 64, GFP_KERNEL);
- if (!tmp)
- return -ENOMEM;
- state = PTR_ALIGN(tmp, 64);
+ if (use_xsave() && !fx_only) {
+ u64 init_bv = xfeatures_mask & ~xfeatures;

if (using_compacted_format()) {
- err = copy_user_to_xstate(&state->xsave, buf_fx);
+ ret = copy_user_to_xstate(&state->xsave, buf_fx);
} else {
- err = __copy_from_user(&state->xsave, buf_fx, state_size);
+ ret = __copy_from_user(&state->xsave, buf_fx, state_size);

- if (!err && state_size > offsetof(struct xregs_state, header))
- err = validate_xstate_header(&state->xsave.header);
+ if (!ret && state_size > offsetof(struct xregs_state, header))
+ ret = validate_xstate_header(&state->xsave.header);
}
+ if (ret)
+ goto err_out;

- if (err || __copy_from_user(&env, buf, sizeof(env))) {
- err = -1;
- } else {
- sanitize_restored_xstate(state, &env, xfeatures, fx_only);
- copy_kernel_to_fpregs(state);
- }
-
- kfree(tmp);
- return err;
- } else {
- union fpregs_state *state;
- void *tmp;
- int ret;
-
- tmp = kzalloc(sizeof(*state) + fpu_kernel_xstate_size + 64, GFP_KERNEL);
- if (!tmp)
- return -ENOMEM;
- state = PTR_ALIGN(tmp, 64);
-
- /*
- * For 64-bit frames and 32-bit fsave frames, restore the user
- * state to the registers directly (with exceptions handled).
- */
- if ((unsigned long)buf_fx % 64)
- fx_only = 1;
-
- if (use_xsave() && !fx_only) {
- u64 init_bv = xfeatures_mask & ~xfeatures;
-
- if (using_compacted_format()) {
- ret = copy_user_to_xstate(&state->xsave, buf_fx);
- } else {
- ret = __copy_from_user(&state->xsave, buf_fx, state_size);
-
- if (!ret && state_size > offsetof(struct xregs_state, header))
- ret = validate_xstate_header(&state->xsave.header);
- }
- if (ret)
- goto err_out;
-
- sanitize_restored_xstate(state, NULL, xfeatures, fx_only);
-
- if (unlikely(init_bv))
- copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
- ret = copy_kernel_to_xregs_err(&state->xsave, xfeatures);
+ sanitize_restored_xstate(state, envp, xfeatures, fx_only);

- } else if (use_fxsr()) {
- ret = __copy_from_user(&state->fxsave, buf_fx, state_size);
- if (ret)
- goto err_out;
+ if (unlikely(init_bv))
+ copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
+ ret = copy_kernel_to_xregs_err(&state->xsave, xfeatures);

- if (use_xsave()) {
- u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE;
- copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
- }
- state->fxsave.mxcsr &= mxcsr_feature_mask;
+ } else if (use_fxsr()) {
+ ret = __copy_from_user(&state->fxsave, buf_fx, state_size);
+ if (ret)
+ goto err_out;

- ret = copy_kernel_to_fxregs_err(&state->fxsave);
- } else {
- ret = __copy_from_user(&state->fsave, buf_fx, state_size);
- if (ret)
- goto err_out;
- ret = copy_kernel_to_fregs_err(&state->fsave);
+ sanitize_restored_xstate(state, envp, xfeatures, fx_only);
+ if (use_xsave()) {
+ u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE;
+ copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
}

-err_out:
- kfree(tmp);
- if (ret) {
- fpu__clear(fpu);
- return -1;
- }
+ ret = copy_kernel_to_fxregs_err(&state->fxsave);
+ } else {
+ ret = __copy_from_user(&state->fsave, buf_fx, state_size);
+ if (ret)
+ goto err_out;
+ ret = copy_kernel_to_fregs_err(&state->fsave);
}

- return 0;
+err_out:
+ kfree(tmp);
+ if (ret)
+ fpu__clear(fpu);
+ return ret;
}

static inline int xstate_sigframe_size(void)
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