signal: Distinguish between kernel_siginfo and siginfo

Linus recently observed that if we did not worry about the padding
member in struct siginfo it is only about 48 bytes, and 48 bytes is
much nicer than 128 bytes for allocating on the stack and copying
around in the kernel.

The obvious thing of only adding the padding when userspace is
including siginfo.h won't work as there are sigframe definitions in
the kernel that embed struct siginfo.

So split siginfo in two; kernel_siginfo and siginfo.  Keeping the
traditional name for the userspace definition.  While the version that
is used internally to the kernel and ultimately will not be padded to
128 bytes is called kernel_siginfo.

The definition of struct kernel_siginfo I have put in include/signal_types.h

A set of buildtime checks has been added to verify the two structures have
the same field offsets.

To make it easy to verify the change kernel_siginfo retains the same
size as siginfo.  The reduction in size comes in a following change.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

1 files changed, 99 insertions, 52 deletions

diff --git a/kernel/signal.c b/kernel/signal.c
index c0e289e62d77..161cad4e448c 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -549,7 +549,7 @@ bool unhandled_signal(struct task_struct *tsk, int sig)
 	return !tsk->ptrace;
 }
 
-static void collect_signal(int sig, struct sigpending *list, siginfo_t *info,
+static void collect_signal(int sig, struct sigpending *list, kernel_siginfo_t *info,
 			   bool *resched_timer)
 {
 	struct sigqueue *q, *first = NULL;
@@ -595,7 +595,7 @@ still_pending:
 }
 
 static int __dequeue_signal(struct sigpending *pending, sigset_t *mask,
-			siginfo_t *info, bool *resched_timer)
+			kernel_siginfo_t *info, bool *resched_timer)
 {
 	int sig = next_signal(pending, mask);
 
@@ -610,7 +610,7 @@ static int __dequeue_signal(struct sigpending *pending, sigset_t *mask,
  *
  * All callers have to hold the siglock.
  */
-int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info)
+int dequeue_signal(struct task_struct *tsk, sigset_t *mask, kernel_siginfo_t *info)
 {
 	bool resched_timer = false;
 	int signr;
@@ -737,12 +737,12 @@ static void flush_sigqueue_mask(sigset_t *mask, struct sigpending *s)
 	}
 }
 
-static inline int is_si_special(const struct siginfo *info)
+static inline int is_si_special(const struct kernel_siginfo *info)
 {
 	return info <= SEND_SIG_PRIV;
 }
 
-static inline bool si_fromuser(const struct siginfo *info)
+static inline bool si_fromuser(const struct kernel_siginfo *info)
 {
 	return info == SEND_SIG_NOINFO ||
 		(!is_si_special(info) && SI_FROMUSER(info));
@@ -767,7 +767,7 @@ static bool kill_ok_by_cred(struct task_struct *t)
  * Bad permissions for sending the signal
  * - the caller must hold the RCU read lock
  */
-static int check_kill_permission(int sig, struct siginfo *info,
+static int check_kill_permission(int sig, struct kernel_siginfo *info,
 				 struct task_struct *t)
 {
 	struct pid *sid;
@@ -1010,7 +1010,7 @@ static inline bool legacy_queue(struct sigpending *signals, int sig)
 }
 
 #ifdef CONFIG_USER_NS
-static inline void userns_fixup_signal_uid(struct siginfo *info, struct task_struct *t)
+static inline void userns_fixup_signal_uid(struct kernel_siginfo *info, struct task_struct *t)
 {
 	if (current_user_ns() == task_cred_xxx(t, user_ns))
 		return;
@@ -1024,13 +1024,13 @@ static inline void userns_fixup_signal_uid(struct siginfo *info, struct task_str
 	rcu_read_unlock();
 }
 #else
-static inline void userns_fixup_signal_uid(struct siginfo *info, struct task_struct *t)
+static inline void userns_fixup_signal_uid(struct kernel_siginfo *info, struct task_struct *t)
 {
 	return;
 }
 #endif
 
-static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
+static int __send_signal(int sig, struct kernel_siginfo *info, struct task_struct *t,
 			enum pid_type type, int from_ancestor_ns)
 {
 	struct sigpending *pending;
@@ -1150,7 +1150,7 @@ ret:
 	return ret;
 }
 
-static int send_signal(int sig, struct siginfo *info, struct task_struct *t,
+static int send_signal(int sig, struct kernel_siginfo *info, struct task_struct *t,
 			enum pid_type type)
 {
 	int from_ancestor_ns = 0;
@@ -1197,12 +1197,12 @@ static int __init setup_print_fatal_signals(char *str)
 __setup("print-fatal-signals=", setup_print_fatal_signals);
 
 int
-__group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
+__group_send_sig_info(int sig, struct kernel_siginfo *info, struct task_struct *p)
 {
 	return send_signal(sig, info, p, PIDTYPE_TGID);
 }
 
-int do_send_sig_info(int sig, struct siginfo *info, struct task_struct *p,
+int do_send_sig_info(int sig, struct kernel_siginfo *info, struct task_struct *p,
 			enum pid_type type)
 {
 	unsigned long flags;
@@ -1228,7 +1228,7 @@ int do_send_sig_info(int sig, struct siginfo *info, struct task_struct *p,
  * that is why we also clear SIGNAL_UNKILLABLE.
  */
 int
-force_sig_info(int sig, struct siginfo *info, struct task_struct *t)
+force_sig_info(int sig, struct kernel_siginfo *info, struct task_struct *t)
 {
 	unsigned long int flags;
 	int ret, blocked, ignored;
@@ -1316,8 +1316,8 @@ struct sighand_struct *__lock_task_sighand(struct task_struct *tsk,
 /*
  * send signal info to all the members of a group
  */
-int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p,
-			enum pid_type type)
+int group_send_sig_info(int sig, struct kernel_siginfo *info,
+			struct task_struct *p, enum pid_type type)
 {
 	int ret;
 
@@ -1336,7 +1336,7 @@ int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p,
  * control characters do (^C, ^Z etc)
  * - the caller must hold at least a readlock on tasklist_lock
  */
-int __kill_pgrp_info(int sig, struct siginfo *info, struct pid *pgrp)
+int __kill_pgrp_info(int sig, struct kernel_siginfo *info, struct pid *pgrp)
 {
 	struct task_struct *p = NULL;
 	int retval, success;
@@ -1351,7 +1351,7 @@ int __kill_pgrp_info(int sig, struct siginfo *info, struct pid *pgrp)
 	return success ? 0 : retval;
 }
 
-int kill_pid_info(int sig, struct siginfo *info, struct pid *pid)
+int kill_pid_info(int sig, struct kernel_siginfo *info, struct pid *pid)
 {
 	int error = -ESRCH;
 	struct task_struct *p;
@@ -1373,7 +1373,7 @@ int kill_pid_info(int sig, struct siginfo *info, struct pid *pid)
 	}
 }
 
-static int kill_proc_info(int sig, struct siginfo *info, pid_t pid)
+static int kill_proc_info(int sig, struct kernel_siginfo *info, pid_t pid)
 {
 	int error;
 	rcu_read_lock();
@@ -1394,7 +1394,7 @@ static inline bool kill_as_cred_perm(const struct cred *cred,
 }
 
 /* like kill_pid_info(), but doesn't use uid/euid of "current" */
-int kill_pid_info_as_cred(int sig, struct siginfo *info, struct pid *pid,
+int kill_pid_info_as_cred(int sig, struct kernel_siginfo *info, struct pid *pid,
 			 const struct cred *cred)
 {
 	int ret = -EINVAL;
@@ -1438,7 +1438,7 @@ EXPORT_SYMBOL_GPL(kill_pid_info_as_cred);
  * is probably wrong.  Should make it like BSD or SYSV.
  */
 
-static int kill_something_info(int sig, struct siginfo *info, pid_t pid)
+static int kill_something_info(int sig, struct kernel_siginfo *info, pid_t pid)
 {
 	int ret;
 
@@ -1482,7 +1482,7 @@ static int kill_something_info(int sig, struct siginfo *info, pid_t pid)
  * These are for backward compatibility with the rest of the kernel source.
  */
 
-int send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
+int send_sig_info(int sig, struct kernel_siginfo *info, struct task_struct *p)
 {
 	/*
 	 * Make sure legacy kernel users don't send in bad values
@@ -1533,7 +1533,7 @@ int force_sig_fault(int sig, int code, void __user *addr
 	___ARCH_SI_IA64(int imm, unsigned int flags, unsigned long isr)
 	, struct task_struct *t)
 {
-	struct siginfo info;
+	struct kernel_siginfo info;
 
 	clear_siginfo(&info);
 	info.si_signo = sig;
@@ -1556,7 +1556,7 @@ int send_sig_fault(int sig, int code, void __user *addr
 	___ARCH_SI_IA64(int imm, unsigned int flags, unsigned long isr)
 	, struct task_struct *t)
 {
-	struct siginfo info;
+	struct kernel_siginfo info;
 
 	clear_siginfo(&info);
 	info.si_signo = sig;
@@ -1576,7 +1576,7 @@ int send_sig_fault(int sig, int code, void __user *addr
 
 int force_sig_mceerr(int code, void __user *addr, short lsb, struct task_struct *t)
 {
-	struct siginfo info;
+	struct kernel_siginfo info;
 
 	WARN_ON((code != BUS_MCEERR_AO) && (code != BUS_MCEERR_AR));
 	clear_siginfo(&info);
@@ -1590,7 +1590,7 @@ int force_sig_mceerr(int code, void __user *addr, short lsb, struct task_struct
 
 int send_sig_mceerr(int code, void __user *addr, short lsb, struct task_struct *t)
 {
-	struct siginfo info;
+	struct kernel_siginfo info;
 
 	WARN_ON((code != BUS_MCEERR_AO) && (code != BUS_MCEERR_AR));
 	clear_siginfo(&info);
@@ -1605,7 +1605,7 @@ EXPORT_SYMBOL(send_sig_mceerr);
 
 int force_sig_bnderr(void __user *addr, void __user *lower, void __user *upper)
 {
-	struct siginfo info;
+	struct kernel_siginfo info;
 
 	clear_siginfo(&info);
 	info.si_signo = SIGSEGV;
@@ -1620,7 +1620,7 @@ int force_sig_bnderr(void __user *addr, void __user *lower, void __user *upper)
 #ifdef SEGV_PKUERR
 int force_sig_pkuerr(void __user *addr, u32 pkey)
 {
-	struct siginfo info;
+	struct kernel_siginfo info;
 
 	clear_siginfo(&info);
 	info.si_signo = SIGSEGV;
@@ -1637,7 +1637,7 @@ int force_sig_pkuerr(void __user *addr, u32 pkey)
  */
 int force_sig_ptrace_errno_trap(int errno, void __user *addr)
 {
-	struct siginfo info;
+	struct kernel_siginfo info;
 
 	clear_siginfo(&info);
 	info.si_signo = SIGTRAP;
@@ -1766,7 +1766,7 @@ ret:
  */
 bool do_notify_parent(struct task_struct *tsk, int sig)
 {
-	struct siginfo info;
+	struct kernel_siginfo info;
 	unsigned long flags;
 	struct sighand_struct *psig;
 	bool autoreap = false;
@@ -1871,7 +1871,7 @@ bool do_notify_parent(struct task_struct *tsk, int sig)
 static void do_notify_parent_cldstop(struct task_struct *tsk,
 				     bool for_ptracer, int why)
 {
-	struct siginfo info;
+	struct kernel_siginfo info;
 	unsigned long flags;
 	struct task_struct *parent;
 	struct sighand_struct *sighand;
@@ -1971,7 +1971,7 @@ static bool sigkill_pending(struct task_struct *tsk)
  * If we actually decide not to stop at all because the tracer
  * is gone, we keep current->exit_code unless clear_code.
  */
-static void ptrace_stop(int exit_code, int why, int clear_code, siginfo_t *info)
+static void ptrace_stop(int exit_code, int why, int clear_code, kernel_siginfo_t *info)
 	__releases(&current->sighand->siglock)
 	__acquires(&current->sighand->siglock)
 {
@@ -2108,7 +2108,7 @@ static void ptrace_stop(int exit_code, int why, int clear_code, siginfo_t *info)
 
 static void ptrace_do_notify(int signr, int exit_code, int why)
 {
-	siginfo_t info;
+	kernel_siginfo_t info;
 
 	clear_siginfo(&info);
 	info.si_signo = signr;
@@ -2289,7 +2289,7 @@ static void do_jobctl_trap(void)
 	}
 }
 
-static int ptrace_signal(int signr, siginfo_t *info)
+static int ptrace_signal(int signr, kernel_siginfo_t *info)
 {
 	/*
 	 * We do not check sig_kernel_stop(signr) but set this marker
@@ -2889,14 +2889,14 @@ enum siginfo_layout siginfo_layout(int sig, int si_code)
 	return layout;
 }
 
-int copy_siginfo_to_user(siginfo_t __user *to, const siginfo_t *from)
+int copy_siginfo_to_user(siginfo_t __user *to, const kernel_siginfo_t *from)
 {
-	if (copy_to_user(to, from , sizeof(struct siginfo)))
+	if (copy_to_user(to, from , sizeof(struct kernel_siginfo)))
 		return -EFAULT;
 	return 0;
 }
 
-int copy_siginfo_from_user(siginfo_t *to, const siginfo_t __user *from)
+int copy_siginfo_from_user(kernel_siginfo_t *to, const siginfo_t __user *from)
 {
 	if (copy_from_user(to, from, sizeof(struct siginfo)))
 		return -EFAULT;
@@ -2905,13 +2905,13 @@ int copy_siginfo_from_user(siginfo_t *to, const siginfo_t __user *from)
 
 #ifdef CONFIG_COMPAT
 int copy_siginfo_to_user32(struct compat_siginfo __user *to,
-			   const struct siginfo *from)
+			   const struct kernel_siginfo *from)
 #if defined(CONFIG_X86_X32_ABI) || defined(CONFIG_IA32_EMULATION)
 {
 	return __copy_siginfo_to_user32(to, from, in_x32_syscall());
 }
 int __copy_siginfo_to_user32(struct compat_siginfo __user *to,
-			     const struct siginfo *from, bool x32_ABI)
+			     const struct kernel_siginfo *from, bool x32_ABI)
 #endif
 {
 	struct compat_siginfo new;
@@ -2995,7 +2995,7 @@ int __copy_siginfo_to_user32(struct compat_siginfo __user *to,
 	return 0;
 }
 
-int copy_siginfo_from_user32(struct siginfo *to,
+int copy_siginfo_from_user32(struct kernel_siginfo *to,
 			     const struct compat_siginfo __user *ufrom)
 {
 	struct compat_siginfo from;
@@ -3085,7 +3085,7 @@ int copy_siginfo_from_user32(struct siginfo *to,
  *  @info: if non-null, the signal's siginfo is returned here
  *  @ts: upper bound on process time suspension
  */
-static int do_sigtimedwait(const sigset_t *which, siginfo_t *info,
+static int do_sigtimedwait(const sigset_t *which, kernel_siginfo_t *info,
 		    const struct timespec *ts)
 {
 	ktime_t *to = NULL, timeout = KTIME_MAX;
@@ -3149,7 +3149,7 @@ SYSCALL_DEFINE4(rt_sigtimedwait, const sigset_t __user *, uthese,
 {
 	sigset_t these;
 	struct timespec ts;
-	siginfo_t info;
+	kernel_siginfo_t info;
 	int ret;
 
 	/* XXX: Don't preclude handling different sized sigset_t's.  */
@@ -3181,7 +3181,7 @@ COMPAT_SYSCALL_DEFINE4(rt_sigtimedwait, compat_sigset_t __user *, uthese,
 {
 	sigset_t s;
 	struct timespec t;
-	siginfo_t info;
+	kernel_siginfo_t info;
 	long ret;
 
 	if (sigsetsize != sizeof(sigset_t))
@@ -3213,7 +3213,7 @@ COMPAT_SYSCALL_DEFINE4(rt_sigtimedwait, compat_sigset_t __user *, uthese,
  */
 SYSCALL_DEFINE2(kill, pid_t, pid, int, sig)
 {
-	struct siginfo info;
+	struct kernel_siginfo info;
 
 	clear_siginfo(&info);
 	info.si_signo = sig;
@@ -3226,7 +3226,7 @@ SYSCALL_DEFINE2(kill, pid_t, pid, int, sig)
 }
 
 static int
-do_send_specific(pid_t tgid, pid_t pid, int sig, struct siginfo *info)
+do_send_specific(pid_t tgid, pid_t pid, int sig, struct kernel_siginfo *info)
 {
 	struct task_struct *p;
 	int error = -ESRCH;
@@ -3257,7 +3257,7 @@ do_send_specific(pid_t tgid, pid_t pid, int sig, struct siginfo *info)
 
 static int do_tkill(pid_t tgid, pid_t pid, int sig)
 {
-	struct siginfo info;
+	struct kernel_siginfo info;
 
 	clear_siginfo(&info);
 	info.si_signo = sig;
@@ -3304,7 +3304,7 @@ SYSCALL_DEFINE2(tkill, pid_t, pid, int, sig)
 	return do_tkill(0, pid, sig);
 }
 
-static int do_rt_sigqueueinfo(pid_t pid, int sig, siginfo_t *info)
+static int do_rt_sigqueueinfo(pid_t pid, int sig, kernel_siginfo_t *info)
 {
 	/* Not even root can pretend to send signals from the kernel.
 	 * Nor can they impersonate a kill()/tgkill(), which adds source info.
@@ -3329,7 +3329,7 @@ static int do_rt_sigqueueinfo(pid_t pid, int sig, siginfo_t *info)
 SYSCALL_DEFINE3(rt_sigqueueinfo, pid_t, pid, int, sig,
 		siginfo_t __user *, uinfo)
 {
-	siginfo_t info;
+	kernel_siginfo_t info;
 	int ret = copy_siginfo_from_user(&info, uinfo);
 	if (unlikely(ret))
 		return ret;
@@ -3342,7 +3342,7 @@ COMPAT_SYSCALL_DEFINE3(rt_sigqueueinfo,
 			int, sig,
 			struct compat_siginfo __user *, uinfo)
 {
-	siginfo_t info;
+	kernel_siginfo_t info;
 	int ret = copy_siginfo_from_user32(&info, uinfo);
 	if (unlikely(ret))
 		return ret;
@@ -3350,7 +3350,7 @@ COMPAT_SYSCALL_DEFINE3(rt_sigqueueinfo,
 }
 #endif
 
-static int do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig, siginfo_t *info)
+static int do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig, kernel_siginfo_t *info)
 {
 	/* This is only valid for single tasks */
 	if (pid <= 0 || tgid <= 0)
@@ -3372,7 +3372,7 @@ static int do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig, siginfo_t *info)
 SYSCALL_DEFINE4(rt_tgsigqueueinfo, pid_t, tgid, pid_t, pid, int, sig,
 		siginfo_t __user *, uinfo)
 {
-	siginfo_t info;
+	kernel_siginfo_t info;
 	int ret = copy_siginfo_from_user(&info, uinfo);
 	if (unlikely(ret))
 		return ret;
@@ -3386,7 +3386,7 @@ COMPAT_SYSCALL_DEFINE4(rt_tgsigqueueinfo,
 			int, sig,
 			struct compat_siginfo __user *, uinfo)
 {
-	siginfo_t info;
+	kernel_siginfo_t info;
 	int ret = copy_siginfo_from_user32(&info, uinfo);
 	if (unlikely(ret))
 		return ret;
@@ -3968,10 +3968,57 @@ __weak const char *arch_vma_name(struct vm_area_struct *vma)
 	return NULL;
 }
 
-void __init signals_init(void)
+static inline void siginfo_buildtime_checks(void)
 {
 	BUILD_BUG_ON(sizeof(struct siginfo) != SI_MAX_SIZE);
 
+	/* Verify the offsets in the two siginfos match */
+#define CHECK_OFFSET(field) \
+	BUILD_BUG_ON(offsetof(siginfo_t, field) != offsetof(kernel_siginfo_t, field))
+
+	/* kill */
+	CHECK_OFFSET(si_pid);
+	CHECK_OFFSET(si_uid);
+
+	/* timer */
+	CHECK_OFFSET(si_tid);
+	CHECK_OFFSET(si_overrun);
+	CHECK_OFFSET(si_value);
+
+	/* rt */
+	CHECK_OFFSET(si_pid);
+	CHECK_OFFSET(si_uid);
+	CHECK_OFFSET(si_value);
+
+	/* sigchld */
+	CHECK_OFFSET(si_pid);
+	CHECK_OFFSET(si_uid);
+	CHECK_OFFSET(si_status);
+	CHECK_OFFSET(si_utime);
+	CHECK_OFFSET(si_stime);
+
+	/* sigfault */
+	CHECK_OFFSET(si_addr);
+	CHECK_OFFSET(si_addr_lsb);
+	CHECK_OFFSET(si_lower);
+	CHECK_OFFSET(si_upper);
+	CHECK_OFFSET(si_pkey);
+
+	/* sigpoll */
+	CHECK_OFFSET(si_band);
+	CHECK_OFFSET(si_fd);
+
+	/* sigsys */
+	CHECK_OFFSET(si_call_addr);
+	CHECK_OFFSET(si_syscall);
+	CHECK_OFFSET(si_arch);
+#undef CHECK_OFFSET
+}
+
+void __init signals_init(void)
+{
+	siginfo_buildtime_checks();
+
 	sigqueue_cachep = KMEM_CACHE(sigqueue, SLAB_PANIC);
 }