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powerpc/signal64: Don't opencode page prefaulting 

Instead of doing a __get_user() from the first and last location
into a tmp var which won't be used, use fault_in_pages_readable()

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/810bd8840ef990a200f58c9dea9abe767ca02a3a.1594146723.git.christophe.leroy@csgroup.eu
This commit is contained in:
Christophe Leroy 2020-07-07 18:32:25 +00:00 committed by Michael Ellerman
parent 020c4831e0
commit 96032f983c
1 changed files with 3 additions and 4 deletions
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7
arch/powerpc/kernel/signal_64.c
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@ -21,6 +21,7 @@
#include <linux/ptrace.h>
#include <linux/ratelimit.h>
#include <linux/syscalls.h>
#include <linux/pagemap.h>
#include <asm/sigcontext.h>
#include <asm/ucontext.h>
@ -634,7 +635,6 @@ static long setup_trampoline(unsigned int syscall, unsigned int __user *tramp)
SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx,
struct ucontext __user *, new_ctx, long, ctx_size)
{
unsigned char tmp;
sigset_t set;
unsigned long new_msr = 0;
int ctx_has_vsx_region = 0;
@ -669,9 +669,8 @@ SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx,
}
if (new_ctx == NULL)
return 0;
if (!access_ok(new_ctx, ctx_size)
|| __get_user(tmp, (u8 __user *) new_ctx)
|| __get_user(tmp, (u8 __user *) new_ctx + ctx_size - 1))
if (!access_ok(new_ctx, ctx_size) ||
fault_in_pages_readable((u8 __user *)new_ctx, ctx_size))
return -EFAULT;
/*