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Message-Id: <20251220215608.434614-6-david.laight.linux@gmail.com>
Date: Sat, 20 Dec 2025 21:56:08 +0000
From: david.laight.linux@...il.com
To: Thomas Gleixner <tglx@...utronix.de>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Peter Zijlstra <peterz@...radead.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Kees Cook <kees@...nel.org>,
linux-kernel@...r.kernel.org,
akpm@...ux-foundation.org,
Al Viro <viro@...iv.linux.org.uk>
Cc: David Laight <david.laight.linux@...il.com>
Subject: [PATCH 5/5] signal: Use scoped_user_access() instead of __put/get_user()
From: David Laight <david.laight.linux@...il.com>
Mechanically change the access_ok() and __get/put_user() to use
scoped_user_read/write_access() and unsafe_get/put_user().
This generates better code with fewer STAC/CLAC pairs.
It also ensures that access_ok() is called near the user accesses.
I failed to find the one for __save_altstack().
Looking at the change, perhaps there should be aliases:
#define scoped_put_user unsafe_put_user
#define scoped_get_user unsafe_get_user
Signed-off-by: David Laight <david.laight.linux@...il.com>
---
kernel/signal.c | 72 ++++++++++++++++++++++++++++---------------------
1 file changed, 42 insertions(+), 30 deletions(-)
diff --git a/kernel/signal.c b/kernel/signal.c
index e42b8bd6922f..806b19041f72 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -4469,10 +4469,16 @@ int restore_altstack(const stack_t __user *uss)
int __save_altstack(stack_t __user *uss, unsigned long sp)
{
struct task_struct *t = current;
- int err = __put_user((void __user *)t->sas_ss_sp, &uss->ss_sp) |
- __put_user(t->sas_ss_flags, &uss->ss_flags) |
- __put_user(t->sas_ss_size, &uss->ss_size);
- return err;
+
+ scoped_user_write_access(uss, Efault) {
+ unsafe_put_user((void __user *)t->sas_ss_sp, &uss->ss_sp, Efault);
+ unsafe_put_user(t->sas_ss_flags, &uss->ss_flags, Efault);
+ unsafe_put_user(t->sas_ss_size, &uss->ss_size, Efault);
+ }
+ return 0;
+
+Efault:
+ return -EFAULT;
}
#ifdef CONFIG_COMPAT
@@ -4705,12 +4711,12 @@ SYSCALL_DEFINE3(sigaction, int, sig,
if (act) {
old_sigset_t mask;
- if (!access_ok(act, sizeof(*act)) ||
- __get_user(new_ka.sa.sa_handler, &act->sa_handler) ||
- __get_user(new_ka.sa.sa_restorer, &act->sa_restorer) ||
- __get_user(new_ka.sa.sa_flags, &act->sa_flags) ||
- __get_user(mask, &act->sa_mask))
- return -EFAULT;
+ scoped_user_read_access(act, Efault) {
+ unsafe_get_user(new_ka.sa.sa_handler, &act->sa_handler, Efault);
+ unsafe_get_user(new_ka.sa.sa_restorer, &act->sa_restorer, Efault);
+ unsafe_get_user(new_ka.sa.sa_flags, &act->sa_flags, Efault);
+ unsafe_get_user(mask, &act->sa_mask, Efault);
+ }
#ifdef __ARCH_HAS_KA_RESTORER
new_ka.ka_restorer = NULL;
#endif
@@ -4720,15 +4726,18 @@ SYSCALL_DEFINE3(sigaction, int, sig,
ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
if (!ret && oact) {
- if (!access_ok(oact, sizeof(*oact)) ||
- __put_user(old_ka.sa.sa_handler, &oact->sa_handler) ||
- __put_user(old_ka.sa.sa_restorer, &oact->sa_restorer) ||
- __put_user(old_ka.sa.sa_flags, &oact->sa_flags) ||
- __put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask))
- return -EFAULT;
+ scoped_user_write_access(oact, Efault) {
+ unsafe_put_user(old_ka.sa.sa_handler, &oact->sa_handler, Efault);
+ unsafe_put_user(old_ka.sa.sa_restorer, &oact->sa_restorer, Efault);
+ unsafe_put_user(old_ka.sa.sa_flags, &oact->sa_flags, Efault);
+ unsafe_put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask, Efault);
+ }
}
return ret;
+
+Efault:
+ return -EFAULT;
}
#endif
#ifdef CONFIG_COMPAT_OLD_SIGACTION
@@ -4742,12 +4751,12 @@ COMPAT_SYSCALL_DEFINE3(sigaction, int, sig,
compat_uptr_t handler, restorer;
if (act) {
- if (!access_ok(act, sizeof(*act)) ||
- __get_user(handler, &act->sa_handler) ||
- __get_user(restorer, &act->sa_restorer) ||
- __get_user(new_ka.sa.sa_flags, &act->sa_flags) ||
- __get_user(mask, &act->sa_mask))
- return -EFAULT;
+ scoped_user_read_access(act, Efault) {
+ unsafe_get_user(handler, &act->sa_handler, Efault);
+ unsafe_get_user(restorer, &act->sa_restorer, Efault);
+ unsafe_get_user(new_ka.sa.sa_flags, &act->sa_flags, Efault);
+ unsafe_get_user(mask, &act->sa_mask, Efault);
+ }
#ifdef __ARCH_HAS_KA_RESTORER
new_ka.ka_restorer = NULL;
@@ -4760,16 +4769,19 @@ COMPAT_SYSCALL_DEFINE3(sigaction, int, sig,
ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
if (!ret && oact) {
- if (!access_ok(oact, sizeof(*oact)) ||
- __put_user(ptr_to_compat(old_ka.sa.sa_handler),
- &oact->sa_handler) ||
- __put_user(ptr_to_compat(old_ka.sa.sa_restorer),
- &oact->sa_restorer) ||
- __put_user(old_ka.sa.sa_flags, &oact->sa_flags) ||
- __put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask))
- return -EFAULT;
+ scoped_user_write_access(oact, Efault) {
+ unsafe_put_user(ptr_to_compat(old_ka.sa.sa_handler),
+ &oact->sa_handler, Efault);
+ unsafe_put_user(ptr_to_compat(old_ka.sa.sa_restorer),
+ &oact->sa_restorer, Efault);
+ unsafe_put_user(old_ka.sa.sa_flags, &oact->sa_flags, Efault);
+ unsafe_put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask, Efault);
+ }
}
return ret;
+
+Efault:
+ return -EFAULT;
}
#endif
--
2.39.5
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