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From: "Christopher M. Riedl" <cmr@codefail.de>
To: linuxppc-dev@lists.ozlabs.org
Subject: [PATCH v7 10/10] powerpc/signal: Use __get_user() to copy sigset_t
Date: Fri, 26 Feb 2021 19:12:59 -0600	[thread overview]
Message-ID: <20210227011259.11992-11-cmr@codefail.de> (raw)
In-Reply-To: <20210227011259.11992-1-cmr@codefail.de>

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>
---
 arch/powerpc/kernel/signal.h    | 7 +++++++
 arch/powerpc/kernel/signal_32.c | 2 +-
 arch/powerpc/kernel/signal_64.c | 4 ++--
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/signal.h b/arch/powerpc/kernel/signal.h
index d8dd76b1dc94..1393876f3814 100644
--- 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 75ee918a120a..c505b444a613 100644
--- 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 00c907022707..debe88055f38 100644
--- 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);
 
-- 
2.26.1


  parent reply	other threads:[~2021-02-27  1:16 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-27  1:12 [PATCH v7 00/10] Improve signal performance on PPC64 with KUAP Christopher M. Riedl
2021-02-27  1:12 ` [PATCH v7 01/10] powerpc/uaccess: Add unsafe_copy_from_user() Christopher M. Riedl
2021-02-27  1:12 ` [PATCH v7 02/10] powerpc/signal: Add unsafe_copy_{vsx, fpr}_from_user() Christopher M. Riedl
2021-02-27  1:12 ` [PATCH v7 03/10] powerpc/signal64: Remove non-inline calls from setup_sigcontext() Christopher M. Riedl
2021-02-27  1:12 ` [PATCH v7 04/10] powerpc: Reference parameter in MSR_TM_ACTIVE() macro Christopher M. Riedl
2021-02-27  1:12 ` [PATCH v7 05/10] powerpc/signal64: Remove TM ifdefery in middle of if/else block Christopher M. Riedl
2021-02-27  1:12 ` [PATCH v7 06/10] powerpc/signal64: Replace setup_sigcontext() w/ unsafe_setup_sigcontext() Christopher M. Riedl
2021-02-27  1:12 ` [PATCH v7 07/10] powerpc/signal64: Replace restore_sigcontext() w/ unsafe_restore_sigcontext() Christopher M. Riedl
2021-02-27  1:12 ` [PATCH v7 08/10] powerpc/signal64: Rewrite handle_rt_signal64() to minimise uaccess switches Christopher M. Riedl
2021-02-27  1:12 ` [PATCH v7 09/10] powerpc/signal64: Rewrite rt_sigreturn() " Christopher M. Riedl
2021-02-27  1:12 ` Christopher M. Riedl [this message]
2021-03-31  1:09 ` [PATCH v7 00/10] Improve signal performance on PPC64 with KUAP Michael Ellerman

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