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Diffstat (limited to 'arch/x86/kernel/signal.c')
-rw-r--r--arch/x86/kernel/signal.c35
1 files changed, 31 insertions, 4 deletions
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 31b6f5dddfc2..2404233336ab 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -61,6 +61,24 @@ static inline int is_x32_frame(struct ksignal *ksig)
}
/*
+ * Enable all pkeys temporarily, so as to ensure that both the current
+ * execution stack as well as the alternate signal stack are writeable.
+ * The application can use any of the available pkeys to protect the
+ * alternate signal stack, and we don't know which one it is, so enable
+ * all. The PKRU register will be reset to init_pkru later in the flow,
+ * in fpu__clear_user_states(), and it is the application's responsibility
+ * to enable the appropriate pkey as the first step in the signal handler
+ * so that the handler does not segfault.
+ */
+static inline u32 sig_prepare_pkru(void)
+{
+ u32 orig_pkru = read_pkru();
+
+ write_pkru(0);
+ return orig_pkru;
+}
+
+/*
* Set up a signal frame.
*/
@@ -84,6 +102,7 @@ get_sigframe(struct ksignal *ksig, struct pt_regs *regs, size_t frame_size,
unsigned long math_size = 0;
unsigned long sp = regs->sp;
unsigned long buf_fx = 0;
+ u32 pkru;
/* redzone */
if (!ia32_frame)
@@ -138,9 +157,17 @@ get_sigframe(struct ksignal *ksig, struct pt_regs *regs, size_t frame_size,
return (void __user *)-1L;
}
+ /* Update PKRU to enable access to the alternate signal stack. */
+ pkru = sig_prepare_pkru();
/* save i387 and extended state */
- if (!copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size))
+ if (!copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size, pkru)) {
+ /*
+ * Restore PKRU to the original, user-defined value; disable
+ * extra pkeys enabled for the alternate signal stack, if any.
+ */
+ write_pkru(pkru);
return (void __user *)-1L;
+ }
return (void __user *)sp;
}
@@ -228,7 +255,7 @@ static void
handle_signal(struct ksignal *ksig, struct pt_regs *regs)
{
bool stepping, failed;
- struct fpu *fpu = &current->thread.fpu;
+ struct fpu *fpu = x86_task_fpu(current);
if (v8086_mode(regs))
save_v86_state((struct kernel_vm86_regs *) regs, VM86_SIGNAL);
@@ -396,14 +423,14 @@ bool sigaltstack_size_valid(size_t ss_size)
if (!fpu_state_size_dynamic() && !strict_sigaltstack_size)
return true;
- fsize += current->group_leader->thread.fpu.perm.__user_state_size;
+ fsize += x86_task_fpu(current->group_leader)->perm.__user_state_size;
if (likely(ss_size > fsize))
return true;
if (strict_sigaltstack_size)
return ss_size > fsize;
- mask = current->group_leader->thread.fpu.perm.__state_perm;
+ mask = x86_task_fpu(current->group_leader)->perm.__state_perm;
if (mask & XFEATURE_MASK_USER_DYNAMIC)
return ss_size > fsize;