Re: [PATCH v4 02/10] powerpc/signal: Add unsafe_copy_{vsx, fpr}_from_user()

Le 28/01/2021 à 11:38, David Laight a écrit :

From: Christopher M. Riedl

quoted

Sent: 28 January 2021 04:04

Reuse the "safe" implementation from signal.c except for calling
unsafe_copy_from_user() to copy into a local buffer.

Signed-off-by: Christopher M. Riedl <redacted>
---
  arch/powerpc/kernel/signal.h | 33 +++++++++++++++++++++++++++++++++
  1 file changed, 33 insertions(+)

diff --git a/arch/powerpc/kernel/signal.h b/arch/powerpc/kernel/signal.h
index 2559a681536e..c18402d625f1 100644
--- a/arch/powerpc/kernel/signal.h
+++ b/arch/powerpc/kernel/signal.h

@@ -53,6 +53,33 @@ unsigned long copy_ckfpr_from_user(struct task_struct *task, void __user *from);
  				&buf[i], label);\
  } while (0)

+#define unsafe_copy_fpr_from_user(task, from, label)	do {		\
+	struct task_struct *__t = task;					\
+	u64 __user *__f = (u64 __user *)from;				\
+	u64 buf[ELF_NFPREG];						\

How big is that buffer?

#define ELF_NFPREG	33

So that's 264 bytes.

That's a bit big but still reasonable I think.

Christophe

Isn't is likely to be reasonably large compared to a reasonable
kernel stack frame.
Especially since this isn't even a leaf function.

quoted

+	int i;								\
+									\
+	unsafe_copy_from_user(buf, __f, ELF_NFPREG * sizeof(double),	\

That really ought to be sizeof(buf).

	David

quoted

+				label);					\
+	for (i = 0; i < ELF_NFPREG - 1; i++)				\
+		__t->thread.TS_FPR(i) = buf[i];				\
+	__t->thread.fp_state.fpscr = buf[i];				\
+} while (0)
+
+#define unsafe_copy_vsx_from_user(task, from, label)	do {		\
+	struct task_struct *__t = task;					\
+	u64 __user *__f = (u64 __user *)from;				\
+	u64 buf[ELF_NVSRHALFREG];					\
+	int i;								\
+									\
+	unsafe_copy_from_user(buf, __f,					\
+				ELF_NVSRHALFREG * sizeof(double),	\
+				label);					\
+	for (i = 0; i < ELF_NVSRHALFREG ; i++)				\
+		__t->thread.fp_state.fpr[i][TS_VSRLOWOFFSET] = buf[i];	\
+} while (0)
+
+
  #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
  #define unsafe_copy_ckfpr_to_user(to, task, label)	do {		\
  	struct task_struct *__t = task;					\

@@ -80,6 +107,10 @@ unsigned long copy_ckfpr_from_user(struct task_struct *task, void __user *from);
  	unsafe_copy_to_user(to, (task)->thread.fp_state.fpr,	\
  			    ELF_NFPREG * sizeof(double), label)

+#define unsafe_copy_fpr_from_user(task, from, label)			\
+	unsafe_copy_from_user((task)->thread.fp_state.fpr, from,	\
+			    ELF_NFPREG * sizeof(double), label)
+
  static inline unsigned long
  copy_fpr_to_user(void __user *to, struct task_struct *task)
  {

@@ -115,6 +146,8 @@ copy_ckfpr_from_user(struct task_struct *task, void __user *from)
  #else
  #define unsafe_copy_fpr_to_user(to, task, label) do { } while (0)

+#define unsafe_copy_fpr_from_user(task, from, label) do { } while (0)
+
  static inline unsigned long
  copy_fpr_to_user(void __user *to, struct task_struct *task)
  {
--

2.26.1

-
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