On Sat, Apr 4, 2015 at 1:22 PM, Yury Norov <yury.norov@xxxxxxxxx> wrote:
> There is a set of syscalls in the kernel about 'sigaction'.
> All they end up with calling the helper 'do_sigaction',
> so the generic scheme is:
>
> - copy user data to kernel;
> - 'do_sigaction';
> - copy kernel data to user.
>
> 'do_sigaction' checks 'signum' parameter before doing its main job.
> If this check fails syscall fails immediately, as well. But at this
> stage first copy is already done. And so there's a potential chance
> having it useless. It may affect performance significantly if user
> data was, say, swapped, and a fault was handled to obtain it.
>
> In this patch, 'signum' sanity check is moved out of 'do_sigaction'
> to a small function 'user_signal'. So we can call it before any copying.
Do you have benchmark results that show the performance impact of that change?
Moving the checks out of do_sigaction() and spreading them all over the kernel
is not nice and needs a good justification.
Having the checks at a central point is much clearer.
> Signed-off-by: Yury Norov <yury.norov@xxxxxxxxx>
> ---
> arch/alpha/kernel/signal.c | 19 +++++++-------
> arch/mips/kernel/signal.c | 10 +++++---
> arch/mips/kernel/signal32.c | 10 +++++---
> arch/sparc/kernel/sys_sparc32.c | 10 ++++----
> arch/sparc/kernel/sys_sparc_32.c | 10 ++++----
> arch/sparc/kernel/sys_sparc_64.c | 10 ++++----
> include/linux/sched.h | 2 +-
> include/linux/signal.h | 5 ++++
> kernel/signal.c | 54 +++++++++++++++++++++-------------------
> 9 files changed, 71 insertions(+), 59 deletions(-)
You add more lines than you delete, please post some hard facts why
it is worth the hassle. :-)
> diff --git a/arch/alpha/kernel/signal.c b/arch/alpha/kernel/signal.c
> index 8dbfb15..5a5db6f 100644
> --- a/arch/alpha/kernel/signal.c
> +++ b/arch/alpha/kernel/signal.c
> @@ -59,7 +59,9 @@ SYSCALL_DEFINE3(osf_sigaction, int, sig,
> struct osf_sigaction __user *, oact)
> {
> struct k_sigaction new_ka, old_ka;
> - int ret;
> +
> + if (!user_signal(sig))
> + return -EINVAL;
>
> if (act) {
> old_sigset_t mask;
> @@ -72,9 +74,9 @@ SYSCALL_DEFINE3(osf_sigaction, int, sig,
> new_ka.ka_restorer = NULL;
> }
>
> - ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
> + do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
>
> - if (!ret && oact) {
> + if (oact) {
> if (!access_ok(VERIFY_WRITE, oact, sizeof(*oact)) ||
> __put_user(old_ka.sa.sa_handler, &oact->sa_handler) ||
> __put_user(old_ka.sa.sa_flags, &oact->sa_flags) ||
> @@ -82,7 +84,7 @@ SYSCALL_DEFINE3(osf_sigaction, int, sig,
> return -EFAULT;
> }
>
> - return ret;
> + return 0;
> }
>
> SYSCALL_DEFINE5(rt_sigaction, int, sig, const struct sigaction __user *, act,
> @@ -90,10 +92,9 @@ SYSCALL_DEFINE5(rt_sigaction, int, sig, const struct sigaction __user *, act,
> size_t, sigsetsize, void __user *, restorer)
> {
> struct k_sigaction new_ka, old_ka;
> - int ret;
>
> /* XXX: Don't preclude handling different sized sigset_t's. */
> - if (sigsetsize != sizeof(sigset_t))
> + if (sigsetsize != sizeof(sigset_t) || !user_signal(sig))
> return -EINVAL;
>
> if (act) {
> @@ -102,14 +103,14 @@ SYSCALL_DEFINE5(rt_sigaction, int, sig, const struct sigaction __user *, act,
> return -EFAULT;
> }
>
> - ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
> + do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
>
> - if (!ret && oact) {
> + if (oact) {
> if (copy_to_user(oact, &old_ka.sa, sizeof(*oact)))
> return -EFAULT;
> }
>
> - return ret;
> + return 0;
> }
>
> /*
> diff --git a/arch/mips/kernel/signal.c b/arch/mips/kernel/signal.c
> index 6a28c79..461a54f 100644
> --- a/arch/mips/kernel/signal.c
> +++ b/arch/mips/kernel/signal.c
> @@ -316,9 +316,11 @@ SYSCALL_DEFINE3(sigaction, int, sig, const struct sigaction __user *, act,
> struct sigaction __user *, oact)
> {
> struct k_sigaction new_ka, old_ka;
> - int ret;
> int err = 0;
>
> + if (!user_signal(sig))
> + return -EINVAL;
> +
> if (act) {
> old_sigset_t mask;
>
> @@ -333,9 +335,9 @@ SYSCALL_DEFINE3(sigaction, int, sig, const struct sigaction __user *, act,
> siginitset(&new_ka.sa.sa_mask, mask);
> }
>
> - ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
> + do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
>
> - if (!ret && oact) {
> + if (oact) {
> if (!access_ok(VERIFY_WRITE, oact, sizeof(*oact)))
> return -EFAULT;
> err |= __put_user(old_ka.sa.sa_flags, &oact->sa_flags);
> @@ -348,7 +350,7 @@ SYSCALL_DEFINE3(sigaction, int, sig, const struct sigaction __user *, act,
> return -EFAULT;
> }
>
> - return ret;
> + return 0;
> }
> #endif
>
> diff --git a/arch/mips/kernel/signal32.c b/arch/mips/kernel/signal32.c
> index 19a7705..7850b02 100644
> --- a/arch/mips/kernel/signal32.c
> +++ b/arch/mips/kernel/signal32.c
> @@ -317,9 +317,11 @@ SYSCALL_DEFINE3(32_sigaction, long, sig, const struct compat_sigaction __user *,
> struct compat_sigaction __user *, oact)
> {
> struct k_sigaction new_ka, old_ka;
> - int ret;
> int err = 0;
>
> + if (!user_signal(sig))
> + return -EINVAL;
> +
> if (act) {
> old_sigset_t mask;
> s32 handler;
> @@ -336,9 +338,9 @@ SYSCALL_DEFINE3(32_sigaction, long, sig, const struct compat_sigaction __user *,
> siginitset(&new_ka.sa.sa_mask, mask);
> }
>
> - ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
> + do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
>
> - if (!ret && oact) {
> + if (oact) {
> if (!access_ok(VERIFY_WRITE, oact, sizeof(*oact)))
> return -EFAULT;
> err |= __put_user(old_ka.sa.sa_flags, &oact->sa_flags);
> @@ -352,7 +354,7 @@ SYSCALL_DEFINE3(32_sigaction, long, sig, const struct compat_sigaction __user *,
> return -EFAULT;
> }
>
> - return ret;
> + return 0;
> }
>
> int copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from)
> diff --git a/arch/sparc/kernel/sys_sparc32.c b/arch/sparc/kernel/sys_sparc32.c
> index 022c30c..5c83f7b 100644
> --- a/arch/sparc/kernel/sys_sparc32.c
> +++ b/arch/sparc/kernel/sys_sparc32.c
> @@ -162,7 +162,7 @@ COMPAT_SYSCALL_DEFINE5(rt_sigaction, int, sig,
> compat_sigset_t set32;
>
> /* XXX: Don't preclude handling different sized sigset_t's. */
> - if (sigsetsize != sizeof(compat_sigset_t))
> + if (sigsetsize != sizeof(compat_sigset_t) || !user_signal(sig))
> return -EINVAL;
>
> if (act) {
> @@ -180,19 +180,19 @@ COMPAT_SYSCALL_DEFINE5(rt_sigaction, int, sig,
> return -EFAULT;
> }
>
> - ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
> + do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
>
> - if (!ret && oact) {
> + if (oact) {
> sigset_to_compat(&set32, &old_ka.sa.sa_mask);
> ret = put_user(ptr_to_compat(old_ka.sa.sa_handler), &oact->sa_handler);
> ret |= copy_to_user(&oact->sa_mask, &set32, sizeof(compat_sigset_t));
> ret |= put_user(old_ka.sa.sa_flags, &oact->sa_flags);
> ret |= put_user(ptr_to_compat(old_ka.sa.sa_restorer), &oact->sa_restorer);
> if (ret)
> - ret = -EFAULT;
> + return -EFAULT;
> }
>
> - return ret;
> + return 0;
> }
>
> asmlinkage compat_ssize_t sys32_pread64(unsigned int fd,
> diff --git a/arch/sparc/kernel/sys_sparc_32.c b/arch/sparc/kernel/sys_sparc_32.c
> index 646988d..ee5b598 100644
> --- a/arch/sparc/kernel/sys_sparc_32.c
> +++ b/arch/sparc/kernel/sys_sparc_32.c
> @@ -20,6 +20,7 @@
> #include <linux/utsname.h>
> #include <linux/smp.h>
> #include <linux/ipc.h>
> +#include <linux/signal.h>
>
> #include <asm/uaccess.h>
> #include <asm/unistd.h>
> @@ -177,10 +178,9 @@ SYSCALL_DEFINE5(rt_sigaction, int, sig,
> size_t, sigsetsize)
> {
> struct k_sigaction new_ka, old_ka;
> - int ret;
>
> /* XXX: Don't preclude handling different sized sigset_t's. */
> - if (sigsetsize != sizeof(sigset_t))
> + if (sigsetsize != sizeof(sigset_t) || !user_signal(sig))
> return -EINVAL;
>
> if (act) {
> @@ -189,14 +189,14 @@ SYSCALL_DEFINE5(rt_sigaction, int, sig,
> return -EFAULT;
> }
>
> - ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
> + do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
>
> - if (!ret && oact) {
> + if (oact) {
> if (copy_to_user(oact, &old_ka.sa, sizeof(*oact)))
> return -EFAULT;
> }
>
> - return ret;
> + return 0;
> }
>
> asmlinkage long sys_getdomainname(char __user *name, int len)
> diff --git a/arch/sparc/kernel/sys_sparc_64.c b/arch/sparc/kernel/sys_sparc_64.c
> index c85403d..b22a753 100644
> --- a/arch/sparc/kernel/sys_sparc_64.c
> +++ b/arch/sparc/kernel/sys_sparc_64.c
> @@ -25,6 +25,7 @@
> #include <linux/random.h>
> #include <linux/export.h>
> #include <linux/context_tracking.h>
> +#include <linux/signal.h>
>
> #include <asm/uaccess.h>
> #include <asm/utrap.h>
> @@ -619,10 +620,9 @@ SYSCALL_DEFINE5(rt_sigaction, int, sig, const struct sigaction __user *, act,
> size_t, sigsetsize)
> {
> struct k_sigaction new_ka, old_ka;
> - int ret;
>
> /* XXX: Don't preclude handling different sized sigset_t's. */
> - if (sigsetsize != sizeof(sigset_t))
> + if (sigsetsize != sizeof(sigset_t) || !user_signal(sig))
> return -EINVAL;
>
> if (act) {
> @@ -631,14 +631,14 @@ SYSCALL_DEFINE5(rt_sigaction, int, sig, const struct sigaction __user *, act,
> return -EFAULT;
> }
>
> - ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
> + do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
>
> - if (!ret && oact) {
> + if (oact) {
> if (copy_to_user(oact, &old_ka.sa, sizeof(*oact)))
> return -EFAULT;
> }
>
> - return ret;
> + return 0;
> }
>
> asmlinkage long sys_kern_features(void)
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 6d77432..4643b7d 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -2394,7 +2394,7 @@ extern int zap_other_threads(struct task_struct *p);
> extern struct sigqueue *sigqueue_alloc(void);
> extern void sigqueue_free(struct sigqueue *);
> extern int send_sigqueue(struct sigqueue *, struct task_struct *, int group);
> -extern int do_sigaction(int, struct k_sigaction *, struct k_sigaction *);
> +extern void do_sigaction(int, struct k_sigaction *, struct k_sigaction *);
>
> static inline void restore_saved_sigmask(void)
> {
> diff --git a/include/linux/signal.h b/include/linux/signal.h
> index ab1e039..129e975 100644
> --- a/include/linux/signal.h
> +++ b/include/linux/signal.h
> @@ -437,6 +437,11 @@ int __save_altstack(stack_t __user *, unsigned long);
> put_user_ex(t->sas_ss_size, &__uss->ss_size); \
> } while (0);
>
> +static inline int user_signal(unsigned long sig)
> +{
> + return sig && valid_signal(sig) && !sig_kernel_only(sig);
> +}
> +
> #ifdef CONFIG_PROC_FS
> struct seq_file;
> extern void render_sigset_t(struct seq_file *, const char *, sigset_t *);
> diff --git a/kernel/signal.c b/kernel/signal.c
> index a390499..5537435 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -3099,15 +3099,12 @@ void kernel_sigaction(int sig, __sighandler_t action)
> }
> EXPORT_SYMBOL(kernel_sigaction);
>
> -int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
> +void do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
> {
> struct task_struct *p = current, *t;
> struct k_sigaction *k;
> sigset_t mask;
>
> - if (!valid_signal(sig) || sig < 1 || (act && sig_kernel_only(sig)))
> - return -EINVAL;
> -
> k = &p->sighand->action[sig-1];
>
> spin_lock_irq(&p->sighand->siglock);
> @@ -3139,8 +3136,8 @@ int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
> }
>
> spin_unlock_irq(&p->sighand->siglock);
> - return 0;
> }
> +EXPORT_SYMBOL(do_sigaction);
>
> static int
> do_sigaltstack (const stack_t __user *uss, stack_t __user *uoss, unsigned long sp)
> @@ -3356,25 +3353,24 @@ SYSCALL_DEFINE4(rt_sigaction, int, sig,
> size_t, sigsetsize)
> {
> struct k_sigaction new_sa, old_sa;
> - int ret = -EINVAL;
>
> /* XXX: Don't preclude handling different sized sigset_t's. */
> - if (sigsetsize != sizeof(sigset_t))
> - goto out;
> + if (sigsetsize != sizeof(sigset_t) || !user_signal(sig))
> + return -EINVAL;
>
> if (act) {
> if (copy_from_user(&new_sa.sa, act, sizeof(new_sa.sa)))
> return -EFAULT;
> }
>
> - ret = do_sigaction(sig, act ? &new_sa : NULL, oact ? &old_sa : NULL);
> + do_sigaction(sig, act ? &new_sa : NULL, oact ? &old_sa : NULL);
>
> - if (!ret && oact) {
> + if (!oact) {
> if (copy_to_user(oact, &old_sa.sa, sizeof(old_sa.sa)))
> return -EFAULT;
> }
> -out:
> - return ret;
> +
> + return 0;
> }
> #ifdef CONFIG_COMPAT
> COMPAT_SYSCALL_DEFINE4(rt_sigaction, int, sig,
> @@ -3390,7 +3386,7 @@ COMPAT_SYSCALL_DEFINE4(rt_sigaction, int, sig,
> int ret;
>
> /* XXX: Don't preclude handling different sized sigset_t's. */
> - if (sigsetsize != sizeof(compat_sigset_t))
> + if (sigsetsize != sizeof(compat_sigset_t) || !user_signal(sig))
> return -EINVAL;
>
> if (act) {
> @@ -3408,8 +3404,8 @@ COMPAT_SYSCALL_DEFINE4(rt_sigaction, int, sig,
> sigset_from_compat(&new_ka.sa.sa_mask, &mask);
> }
>
> - ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
> - if (!ret && oact) {
> + do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
> + if (oact) {
> sigset_to_compat(&mask, &old_ka.sa.sa_mask);
> ret = put_user(ptr_to_compat(old_ka.sa.sa_handler),
> &oact->sa_handler);
> @@ -3431,7 +3427,9 @@ SYSCALL_DEFINE3(sigaction, int, sig,
> struct old_sigaction __user *, oact)
> {
> struct k_sigaction new_ka, old_ka;
> - int ret;
> +
> + if (!user_signal(sig))
> + return -EINVAL;
>
> if (act) {
> old_sigset_t mask;
> @@ -3447,9 +3445,9 @@ SYSCALL_DEFINE3(sigaction, int, sig,
> siginitset(&new_ka.sa.sa_mask, mask);
> }
>
> - ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
> + do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
>
> - if (!ret && oact) {
> + if (oact) {
> if (!access_ok(VERIFY_WRITE, oact, sizeof(*oact)) ||
> __put_user(old_ka.sa.sa_handler, &oact->sa_handler) ||
> __put_user(old_ka.sa.sa_restorer, &oact->sa_restorer) ||
> @@ -3458,7 +3456,7 @@ SYSCALL_DEFINE3(sigaction, int, sig,
> return -EFAULT;
> }
>
> - return ret;
> + return 0;
> }
> #endif
> #ifdef CONFIG_COMPAT_OLD_SIGACTION
> @@ -3467,10 +3465,12 @@ COMPAT_SYSCALL_DEFINE3(sigaction, int, sig,
> struct compat_old_sigaction __user *, oact)
> {
> struct k_sigaction new_ka, old_ka;
> - int ret;
> compat_old_sigset_t mask;
> compat_uptr_t handler, restorer;
>
> + if (!user_signal(sig))
> + return -EINVAL;
> +
> if (act) {
> if (!access_ok(VERIFY_READ, act, sizeof(*act)) ||
> __get_user(handler, &act->sa_handler) ||
> @@ -3487,9 +3487,9 @@ COMPAT_SYSCALL_DEFINE3(sigaction, int, sig,
> siginitset(&new_ka.sa.sa_mask, mask);
> }
>
> - ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
> + do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
>
> - if (!ret && oact) {
> + if (oact) {
> if (!access_ok(VERIFY_WRITE, oact, sizeof(*oact)) ||
> __put_user(ptr_to_compat(old_ka.sa.sa_handler),
> &oact->sa_handler) ||
> @@ -3499,7 +3499,7 @@ COMPAT_SYSCALL_DEFINE3(sigaction, int, sig,
> __put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask))
> return -EFAULT;
> }
> - return ret;
> + return 0;
> }
> #endif
>
> @@ -3533,15 +3533,17 @@ SYSCALL_DEFINE1(ssetmask, int, newmask)
> SYSCALL_DEFINE2(signal, int, sig, __sighandler_t, handler)
> {
> struct k_sigaction new_sa, old_sa;
> - int ret;
> +
> + if (!user_signal(sig))
> + return -EINVAL;
>
> new_sa.sa.sa_handler = handler;
> new_sa.sa.sa_flags = SA_ONESHOT | SA_NOMASK;
> sigemptyset(&new_sa.sa.sa_mask);
>
> - ret = do_sigaction(sig, &new_sa, &old_sa);
> + do_sigaction(sig, &new_sa, &old_sa);
>
> - return ret ? ret : (unsigned long)old_sa.sa.sa_handler;
> + return (unsigned long) old_sa.sa.sa_handler;
> }
> #endif /* __ARCH_WANT_SYS_SIGNAL */
>
> --
> 2.1.0
>
> --
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> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
--
Thanks,
//richard
