[PATCH 4.14 64/88] x86/fpu: Reset state for all signal restore failures

Sasha Levin
2021-06-28T15:13:15Z

From: Thomas Gleixner <tglx@linutronix.de>

commit efa165504943f2128d50f63de0c02faf6dcceb0d upstream.

If access_ok() or fpregs_soft_set() fails in __fpu__restore_sig() then the
function just returns but does not clear the FPU state as it does for all
other fatal failures.

Clear the FPU state for these failures as well.

Fixes: 72a671ced66d ("x86, fpu: Unify signal handling code paths for x86 and x86_64 kernels")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/87mtryyhhz.ffs@nanos.tec.linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kernel/fpu/signal.c | 31 ++++++++++++++++++++-----------
1 file changed, 20 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index d99a8ee9e185..86a231338bbf 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -272,6 +272,7 @@ 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 ret = 0;

ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
IS_ENABLED(CONFIG_IA32_EMULATION));
@@ -281,15 +282,21 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
return 0;
}

- if (!access_ok(VERIFY_READ, buf, size))
- return -EACCES;
+ if (!access_ok(VERIFY_READ, buf, size)) {
+ ret = -EACCES;
+ goto out_err;
+ }

fpu__initialize(fpu);

- if (!static_cpu_has(X86_FEATURE_FPU))
- return fpregs_soft_set(current, NULL,
- 0, sizeof(struct user_i387_ia32_struct),
- NULL, buf) != 0;
+ if (!static_cpu_has(X86_FEATURE_FPU)) {
+ ret = fpregs_soft_set(current, NULL,
+ 0, sizeof(struct user_i387_ia32_struct),
+ NULL, buf) != 0;
+ if (ret)
+ goto out_err;
+ return 0;
+ }

if (use_xsave()) {
struct _fpx_sw_bytes fx_sw_user;
@@ -349,6 +356,7 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
fpu__restore(fpu);
local_bh_enable();

+ /* Failure is already handled */
return err;
} else {
/*
@@ -356,13 +364,14 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
* state to the registers directly (with exceptions handled).
*/
user_fpu_begin();
- if (copy_user_to_fpregs_zeroing(buf_fx, xfeatures, fx_only)) {
- fpu__clear(fpu);
- return -1;
- }
+ if (!copy_user_to_fpregs_zeroing(buf_fx, xfeatures, fx_only))
+ return 0;
+ ret = -1;
}

- return 0;
+out_err:
+ fpu__clear(fpu);
+ return ret;
}

static inline int xstate_sigframe_size(void)
--
2.30.2