powerpc/signal: Use __get_user() to copy sigset_t

Usually sigset_t is exactly 8B which is a "trivial" size and does not
warrant using __copy_from_user(). Use __get_user() directly in
anticipation of future work to remove the trivial size optimizations
from __copy_from_user().

The ppc32 implementation of get_sigset_t() previously called
copy_from_user() which, unlike __copy_from_user(), calls access_ok().
Replacing this w/ __get_user() (no access_ok()) is fine here since both
callsites in signal_32.c are preceded by an earlier access_ok().

Signed-off-by: Christopher M. Riedl <cmr@codefail.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210227011259.11992-11-cmr@codefail.de

diff --git a/arch/powerpc/kernel/signal.h b/arch/powerpc/kernel/signal.h
index d8dd76b1dc9404a401749ba4b0e205d3154396fc..1393876f38143fe733d0170a42a31012c17fa6e3 100644 (file)
--- a/arch/powerpc/kernel/signal.h
+++ b/arch/powerpc/kernel/signal.h
@@ -19,6 +19,13 @@ extern int handle_signal32(struct ksignal *ksig, sigset_t *oldset,
 extern int handle_rt_signal32(struct ksignal *ksig, sigset_t *oldset,
                              struct task_struct *tsk);
 
+static inline int __get_user_sigset(sigset_t *dst, const sigset_t __user *src)
+{
+       BUILD_BUG_ON(sizeof(sigset_t) != sizeof(u64));
+
+       return __get_user(dst->sig[0], (u64 __user *)&src->sig[0]);
+}
+
 #ifdef CONFIG_VSX
 extern unsigned long copy_vsx_to_user(void __user *to,
                                      struct task_struct *task);

diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index 75ee918a120a5e67f499e53e0c1f7df5aabeba13..c505b444a6131ee6d0b472b9af36ce92a8521789 100644 (file)
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -144,7 +144,7 @@ static inline int restore_general_regs(struct pt_regs *regs,
 
 static inline int get_sigset_t(sigset_t *set, const sigset_t __user *uset)
 {
-       return copy_from_user(set, uset, sizeof(*uset));
+       return __get_user_sigset(set, uset);
 }
 
 #define to_user_ptr(p)         ((unsigned long)(p))

diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index e7d612e82363859ae76e536ba68126032b5ab6f6..e10459f11f8e033c8fc4ea508c6887aa203c0fcd 100644 (file)
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -708,7 +708,7 @@ SYSCALL_DEFINE3(swapcontext, struct ucontext __user *, old_ctx,
         * We kill the task with a SIGSEGV in this situation.
         */
 
-       if (__copy_from_user(&set, &new_ctx->uc_sigmask, sizeof(set)))
+       if (__get_user_sigset(&set, &new_ctx->uc_sigmask))
                do_exit(SIGSEGV);
        set_current_blocked(&set);
 
@@ -747,7 +747,7 @@ SYSCALL_DEFINE0(rt_sigreturn)
        if (!access_ok(uc, sizeof(*uc)))
                goto badframe;
 
-       if (__copy_from_user(&set, &uc->uc_sigmask, sizeof(set)))
+       if (__get_user_sigset(&set, &uc->uc_sigmask))
                goto badframe;
        set_current_blocked(&set);