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do_sigaltstack(): lift copying to/from userland into callers

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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2017-05-27 00:29:34 -04:00
parent 613763a1f0
commit bcfe8ad8ef
1 changed files with 46 additions and 61 deletions
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107
kernel/signal.c
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@ -3113,78 +3113,68 @@ int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
}
static int
do_sigaltstack (const stack_t __user *uss, stack_t __user *uoss, unsigned long sp)
do_sigaltstack (const stack_t *ss, stack_t *oss, unsigned long sp)
{
stack_t oss;
int error;
struct task_struct *t = current;
oss.ss_sp = (void __user *) current->sas_ss_sp;
oss.ss_size = current->sas_ss_size;
oss.ss_flags = sas_ss_flags(sp) |
(current->sas_ss_flags & SS_FLAG_BITS);
if (oss) {
memset(oss, 0, sizeof(stack_t));
oss->ss_sp = (void __user *) t->sas_ss_sp;
oss->ss_size = t->sas_ss_size;
oss->ss_flags = sas_ss_flags(sp) |
(current->sas_ss_flags & SS_FLAG_BITS);
}
if (uss) {
void __user *ss_sp;
size_t ss_size;
unsigned ss_flags;
if (ss) {
void __user *ss_sp = ss->ss_sp;
size_t ss_size = ss->ss_size;
unsigned ss_flags = ss->ss_flags;
int ss_mode;
error = -EFAULT;
if (!access_ok(VERIFY_READ, uss, sizeof(*uss)))
goto out;
error = __get_user(ss_sp, &uss->ss_sp) |
__get_user(ss_flags, &uss->ss_flags) |
__get_user(ss_size, &uss->ss_size);
if (error)
goto out;
error = -EPERM;
if (on_sig_stack(sp))
goto out;
if (unlikely(on_sig_stack(sp)))
return -EPERM;
ss_mode = ss_flags & ~SS_FLAG_BITS;
error = -EINVAL;
if (ss_mode != SS_DISABLE && ss_mode != SS_ONSTACK &&
ss_mode != 0)
goto out;
if (unlikely(ss_mode != SS_DISABLE && ss_mode != SS_ONSTACK &&
ss_mode != 0))
return -EINVAL;
if (ss_mode == SS_DISABLE) {
ss_size = 0;
ss_sp = NULL;
} else {
error = -ENOMEM;
if (ss_size < MINSIGSTKSZ)
goto out;
if (unlikely(ss_size < MINSIGSTKSZ))
return -ENOMEM;
}
current->sas_ss_sp = (unsigned long) ss_sp;
current->sas_ss_size = ss_size;
current->sas_ss_flags = ss_flags;
t->sas_ss_sp = (unsigned long) ss_sp;
t->sas_ss_size = ss_size;
t->sas_ss_flags = ss_flags;
}
error = 0;
if (uoss) {
error = -EFAULT;
if (!access_ok(VERIFY_WRITE, uoss, sizeof(*uoss)))
goto out;
error = __put_user(oss.ss_sp, &uoss->ss_sp) |
__put_user(oss.ss_size, &uoss->ss_size) |
__put_user(oss.ss_flags, &uoss->ss_flags);
}
out:
return error;
return 0;
}
SYSCALL_DEFINE2(sigaltstack,const stack_t __user *,uss, stack_t __user *,uoss)
{
return do_sigaltstack(uss, uoss, current_user_stack_pointer());
stack_t new, old;
int err;
if (uss && copy_from_user(&new, uss, sizeof(stack_t)))
return -EFAULT;
err = do_sigaltstack(uss ? &new : NULL, uoss ? &old : NULL,
current_user_stack_pointer());
if (!err && uoss && copy_to_user(uoss, &old, sizeof(stack_t)))
err = -EFAULT;
return err;
}
int restore_altstack(const stack_t __user *uss)
{
int err = do_sigaltstack(uss, NULL, current_user_stack_pointer());
stack_t new;
if (copy_from_user(&new, uss, sizeof(stack_t)))
return -EFAULT;
(void)do_sigaltstack(&new, NULL, current_user_stack_pointer());
/* squash all but EFAULT for now */
return err == -EFAULT ? err : 0;
return 0;
}
int __save_altstack(stack_t __user *uss, unsigned long sp)
@ -3207,29 +3197,24 @@ COMPAT_SYSCALL_DEFINE2(sigaltstack,
{
stack_t uss, uoss;
int ret;
mm_segment_t seg;
if (uss_ptr) {
compat_stack_t uss32;
memset(&uss, 0, sizeof(stack_t));
if (copy_from_user(&uss32, uss_ptr, sizeof(compat_stack_t)))
return -EFAULT;
uss.ss_sp = compat_ptr(uss32.ss_sp);
uss.ss_flags = uss32.ss_flags;
uss.ss_size = uss32.ss_size;
}
seg = get_fs();
set_fs(KERNEL_DS);
ret = do_sigaltstack((stack_t __force __user *) (uss_ptr ? &uss : NULL),
(stack_t __force __user *) &uoss,
ret = do_sigaltstack(uss_ptr ? &uss : NULL, &uoss,
compat_user_stack_pointer());
set_fs(seg);
if (ret >= 0 && uoss_ptr) {
if (!access_ok(VERIFY_WRITE, uoss_ptr, sizeof(compat_stack_t)) ||
__put_user(ptr_to_compat(uoss.ss_sp), &uoss_ptr->ss_sp) ||
__put_user(uoss.ss_flags, &uoss_ptr->ss_flags) ||
__put_user(uoss.ss_size, &uoss_ptr->ss_size))
compat_stack_t old;
memset(&old, 0, sizeof(old));
old.ss_sp = ptr_to_compat(uoss.ss_sp);
old.ss_flags = uoss.ss_flags;
old.ss_size = uoss.ss_size;
if (copy_to_user(uoss_ptr, &old, sizeof(compat_stack_t)))
ret = -EFAULT;
}
return ret;