2018-04-24 16:06:10

by Christophe Leroy

Subject: [PATCH v2] powerpc/signal32: Use fault_in_pages_readable() to prefault user context

Use fault_in_pages_readable() to prefault user context
instead of open coding

Signed-off-by: Christophe Leroy <[email protected]>
---
v2: using sizeof(*ctx) as size of ctx instead of 1

arch/powerpc/kernel/signal_32.c | 13 +++++--------
1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index 492f03451877..4a9e4d6d555b 100644
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -25,6 +25,7 @@
#include <linux/errno.h>
#include <linux/elf.h>
#include <linux/ptrace.h>
+#include <linux/pagemap.h>
#include <linux/ratelimit.h>
#ifdef CONFIG_PPC64
#include <linux/syscalls.h>
@@ -1045,7 +1046,6 @@ long sys_swapcontext(struct ucontext __user *old_ctx,
struct ucontext __user *new_ctx,
int ctx_size, int r6, int r7, int r8, struct pt_regs *regs)
{
- unsigned char tmp __maybe_unused;
int ctx_has_vsx_region = 0;

#ifdef CONFIG_PPC64
@@ -1109,9 +1109,8 @@ long sys_swapcontext(struct ucontext __user *old_ctx,
}
if (new_ctx == NULL)
return 0;
- if (!access_ok(VERIFY_READ, new_ctx, ctx_size)
- || __get_user(tmp, (u8 __user *) new_ctx)
- || __get_user(tmp, (u8 __user *) new_ctx + ctx_size - 1))
+ if (!access_ok(VERIFY_READ, new_ctx, ctx_size) ||
+ fault_in_pages_readable((u8 __user *)new_ctx, ctx_size))
return -EFAULT;

/*
@@ -1231,7 +1230,6 @@ int sys_debug_setcontext(struct ucontext __user *ctx,
{
struct sig_dbg_op op;
int i;
- unsigned char tmp __maybe_unused;
unsigned long new_msr = regs->msr;
#ifdef CONFIG_PPC_ADV_DEBUG_REGS
unsigned long new_dbcr0 = current->thread.debug.dbcr0;
@@ -1287,9 +1285,8 @@ int sys_debug_setcontext(struct ucontext __user *ctx,
current->thread.debug.dbcr0 = new_dbcr0;
#endif

- if (!access_ok(VERIFY_READ, ctx, sizeof(*ctx))
- || __get_user(tmp, (u8 __user *) ctx)
- || __get_user(tmp, (u8 __user *) (ctx + 1) - 1))
+ if (!access_ok(VERIFY_READ, ctx, sizeof(*ctx)) ||
+ fault_in_pages_readable((u8 __user *)ctx, sizeof(*ctx)))
return -EFAULT;

/*
--
2.13.3

2018-04-24 18:56:43

by Mathieu Malaterre

Subject: Re: [PATCH v2] powerpc/signal32: Use fault_in_pages_readable() to prefault user context

On Tue, Apr 24, 2018 at 6:04 PM, Christophe Leroy
<[email protected]> wrote:
> Use fault_in_pages_readable() to prefault user context
> instead of open coding
>
> Signed-off-by: Christophe Leroy <[email protected]>
> ---
> v2: using sizeof(*ctx) as size of ctx instead of 1
>
> arch/powerpc/kernel/signal_32.c | 13 +++++--------
> 1 file changed, 5 insertions(+), 8 deletions(-)
>
> diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
> index 492f03451877..4a9e4d6d555b 100644
> --- a/arch/powerpc/kernel/signal_32.c
> +++ b/arch/powerpc/kernel/signal_32.c
> @@ -25,6 +25,7 @@
> #include <linux/errno.h>
> #include <linux/elf.h>
> #include <linux/ptrace.h>
> +#include <linux/pagemap.h>
> #include <linux/ratelimit.h>
> #ifdef CONFIG_PPC64
> #include <linux/syscalls.h>
> @@ -1045,7 +1046,6 @@ long sys_swapcontext(struct ucontext __user *old_ctx,
> struct ucontext __user *new_ctx,
> int ctx_size, int r6, int r7, int r8, struct pt_regs *regs)
> {
> - unsigned char tmp __maybe_unused;
> int ctx_has_vsx_region = 0;
>
> #ifdef CONFIG_PPC64
> @@ -1109,9 +1109,8 @@ long sys_swapcontext(struct ucontext __user *old_ctx,
> }
> if (new_ctx == NULL)
> return 0;
> - if (!access_ok(VERIFY_READ, new_ctx, ctx_size)
> - || __get_user(tmp, (u8 __user *) new_ctx)
> - || __get_user(tmp, (u8 __user *) new_ctx + ctx_size - 1))
> + if (!access_ok(VERIFY_READ, new_ctx, ctx_size) ||
> + fault_in_pages_readable((u8 __user *)new_ctx, ctx_size))
> return -EFAULT;
>
> /*
> @@ -1231,7 +1230,6 @@ int sys_debug_setcontext(struct ucontext __user *ctx,
> {
> struct sig_dbg_op op;
> int i;
> - unsigned char tmp __maybe_unused;
> unsigned long new_msr = regs->msr;
> #ifdef CONFIG_PPC_ADV_DEBUG_REGS
> unsigned long new_dbcr0 = current->thread.debug.dbcr0;
> @@ -1287,9 +1285,8 @@ int sys_debug_setcontext(struct ucontext __user *ctx,
> current->thread.debug.dbcr0 = new_dbcr0;
> #endif
>
> - if (!access_ok(VERIFY_READ, ctx, sizeof(*ctx))
> - || __get_user(tmp, (u8 __user *) ctx)
> - || __get_user(tmp, (u8 __user *) (ctx + 1) - 1))
> + if (!access_ok(VERIFY_READ, ctx, sizeof(*ctx)) ||
> + fault_in_pages_readable((u8 __user *)ctx, sizeof(*ctx)))
> return -EFAULT;
>
> /*
> --
> 2.13.3
>


Looks good:

Reviewed-by: Mathieu Malaterre <[email protected]>

Thanks for fixing my previous attempt !

2018-06-04 14:16:44

by Michael Ellerman

Subject: Re: [v2] powerpc/signal32: Use fault_in_pages_readable() to prefault user context

On Tue, 2018-04-24 at 16:04:25 UTC, Christophe Leroy wrote:
> Use fault_in_pages_readable() to prefault user context
> instead of open coding
>
> Signed-off-by: Christophe Leroy <[email protected]>
> Reviewed-by: Mathieu Malaterre <[email protected]>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/56b04d568f880a48d892e840cfaf4e

cheers