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

[David Laight <David.Laight@ACULAB.COM>]

From: Christopher M. Riedl
> 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 <cmr@codefail.de>
> ---
>  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?
Isn't is likely to be reasonably large compared to a reasonable
kernel stack frame.
Especially since this isn't even a leaf function.

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

That really ought to be sizeof(buf).

	David


> +				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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