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Subject[RFC][PATCH v2 12/22] x86: get rid of put_user_try in {ia32,x32}_setup_rt_frame()
Date
From: Al Viro <viro@zeniv.linux.org.uk>

Straightforward, except for compat_save_altstack_ex() stuck in those.
Replace that thing with an analogue that would use unsafe_put_user()
instead of put_user_ex() (called unsafe_compat_save_altstack()) and
be done with that...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
arch/x86/ia32/ia32_signal.c | 50 +++++++++++++++++++++++----------------------
arch/x86/kernel/signal.c | 33 ++++++++++++++++--------------
include/linux/compat.h | 9 ++++----
3 files changed, 49 insertions(+), 43 deletions(-)

diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
index af673ec23a2d..a96995aa23da 100644
--- a/arch/x86/ia32/ia32_signal.c
+++ b/arch/x86/ia32/ia32_signal.c
@@ -326,35 +326,34 @@ int ia32_setup_rt_frame(int sig, struct ksignal *ksig,

frame = get_sigframe(ksig, regs, sizeof(*frame), &fpstate);

- if (!access_ok(frame, sizeof(*frame)))
+ if (!user_access_begin(frame, sizeof(*frame)))
return -EFAULT;

- put_user_try {
- put_user_ex(sig, &frame->sig);
- put_user_ex(ptr_to_compat(&frame->info), &frame->pinfo);
- put_user_ex(ptr_to_compat(&frame->uc), &frame->puc);
+ unsafe_put_user(sig, &frame->sig, Efault);
+ unsafe_put_user(ptr_to_compat(&frame->info), &frame->pinfo, Efault);
+ unsafe_put_user(ptr_to_compat(&frame->uc), &frame->puc, Efault);

- /* Create the ucontext. */
- if (static_cpu_has(X86_FEATURE_XSAVE))
- put_user_ex(UC_FP_XSTATE, &frame->uc.uc_flags);
- else
- put_user_ex(0, &frame->uc.uc_flags);
- put_user_ex(0, &frame->uc.uc_link);
- compat_save_altstack_ex(&frame->uc.uc_stack, regs->sp);
+ /* Create the ucontext. */
+ if (static_cpu_has(X86_FEATURE_XSAVE))
+ unsafe_put_user(UC_FP_XSTATE, &frame->uc.uc_flags, Efault);
+ else
+ unsafe_put_user(0, &frame->uc.uc_flags, Efault);
+ unsafe_put_user(0, &frame->uc.uc_link, Efault);
+ unsafe_compat_save_altstack(&frame->uc.uc_stack, regs->sp, Efault);

- if (ksig->ka.sa.sa_flags & SA_RESTORER)
- restorer = ksig->ka.sa.sa_restorer;
- else
- restorer = current->mm->context.vdso +
- vdso_image_32.sym___kernel_rt_sigreturn;
- put_user_ex(ptr_to_compat(restorer), &frame->pretcode);
+ if (ksig->ka.sa.sa_flags & SA_RESTORER)
+ restorer = ksig->ka.sa.sa_restorer;
+ else
+ restorer = current->mm->context.vdso +
+ vdso_image_32.sym___kernel_rt_sigreturn;
+ unsafe_put_user(ptr_to_compat(restorer), &frame->pretcode, Efault);

- /*
- * Not actually used anymore, but left because some gdb
- * versions need it.
- */
- put_user_ex(*((u64 *)&code), (u64 __user *)frame->retcode);
- } put_user_catch(err);
+ /*
+ * Not actually used anymore, but left because some gdb
+ * versions need it.
+ */
+ unsafe_put_user(*((u64 *)&code), (u64 __user *)frame->retcode, Efault);
+ user_access_end();

err |= __copy_siginfo_to_user32(&frame->info, &ksig->info, false);
err |= ia32_setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
@@ -380,4 +379,7 @@ int ia32_setup_rt_frame(int sig, struct ksignal *ksig,
regs->ss = __USER32_DS;

return 0;
+Efault:
+ user_access_end();
+ return -EFAULT;
}
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 3b4ca484cfc2..29abad29aaa1 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -529,6 +529,9 @@ static int x32_setup_rt_frame(struct ksignal *ksig,
int err = 0;
void __user *fpstate = NULL;

+ if (!(ksig->ka.sa.sa_flags & SA_RESTORER))
+ return -EFAULT;
+
frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fpstate);

if (!access_ok(frame, sizeof(*frame)))
@@ -541,22 +544,17 @@ static int x32_setup_rt_frame(struct ksignal *ksig,

uc_flags = frame_uc_flags(regs);

- put_user_try {
- /* Create the ucontext. */
- put_user_ex(uc_flags, &frame->uc.uc_flags);
- put_user_ex(0, &frame->uc.uc_link);
- compat_save_altstack_ex(&frame->uc.uc_stack, regs->sp);
- put_user_ex(0, &frame->uc.uc__pad0);
+ if (!user_access_begin(frame, sizeof(*frame)))
+ return -EFAULT;

- if (ksig->ka.sa.sa_flags & SA_RESTORER) {
- restorer = ksig->ka.sa.sa_restorer;
- } else {
- /* could use a vstub here */
- restorer = NULL;
- err |= -EFAULT;
- }
- put_user_ex(restorer, (unsigned long __user *)&frame->pretcode);
- } put_user_catch(err);
+ /* Create the ucontext. */
+ unsafe_put_user(uc_flags, &frame->uc.uc_flags, Efault);
+ unsafe_put_user(0, &frame->uc.uc_link, Efault);
+ unsafe_compat_save_altstack(&frame->uc.uc_stack, regs->sp, Efault);
+ unsafe_put_user(0, &frame->uc.uc__pad0, Efault);
+ restorer = ksig->ka.sa.sa_restorer;
+ unsafe_put_user(restorer, (unsigned long __user *)&frame->pretcode, Efault);
+ user_access_end();

err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
regs, set->sig[0]);
@@ -582,6 +580,11 @@ static int x32_setup_rt_frame(struct ksignal *ksig,
#endif /* CONFIG_X86_X32_ABI */

return 0;
+#ifdef CONFIG_X86_X32_ABI
+Efault:
+ user_access_end();
+ return -EFAULT;
+#endif
}

/*
diff --git a/include/linux/compat.h b/include/linux/compat.h
index 11083d84eb23..224ecb4fffd4 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -483,12 +483,13 @@ extern void __user *compat_alloc_user_space(unsigned long len);

int compat_restore_altstack(const compat_stack_t __user *uss);
int __compat_save_altstack(compat_stack_t __user *, unsigned long);
-#define compat_save_altstack_ex(uss, sp) do { \
+#define unsafe_compat_save_altstack(uss, sp, label) do { \
compat_stack_t __user *__uss = uss; \
struct task_struct *t = current; \
- put_user_ex(ptr_to_compat((void __user *)t->sas_ss_sp), &__uss->ss_sp); \
- put_user_ex(t->sas_ss_flags, &__uss->ss_flags); \
- put_user_ex(t->sas_ss_size, &__uss->ss_size); \
+ unsafe_put_user(ptr_to_compat((void __user *)t->sas_ss_sp), \
+ &__uss->ss_sp, label); \
+ unsafe_put_user(t->sas_ss_flags, &__uss->ss_flags, label); \
+ unsafe_put_user(t->sas_ss_size, &__uss->ss_size, label); \
if (t->sas_ss_flags & SS_AUTODISARM) \
sas_ss_reset(t); \
} while (0);
--
2.11.0
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