On Tue, Apr 24, 2018 at 4:45 PM, Mathieu Malaterre <ma...@debian.org> wrote:
> On Tue, Apr 24, 2018 at 4:17 PM, Christophe Leroy
> <christophe.le...@c-s.fr> wrote:
>> Use fault_in_pages_readable() to prefault user context
>> instead of open coding
>>
>> Signed-off-by: Christophe Leroy <christophe.le...@c-s.fr>
>> ---
>> 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..cfacb2726152 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, 1))
>
> I believe you meant:
>
> fault_in_pages_readable((u8 __user *)new_ctx, ctx_size)
>
> Since (u8 __user *) (ctx + 1) - 1 really is (u8 __user *) new_ctx + ctx_size
> - 1
Without the copy/paste errors:
[...]
fault_in_pages_readable((u8 __user *)ctx, sizeof(*ctx))
Since (u8 __user *) (ctx + 1) - 1 really is (u8 __user *) ctx + sizeof(*ctx) - 1
[...]
>> return -EFAULT;
>>
>> /*
>> --
>> 2.13.3
>>
