signal: Unify and correct copy_siginfo_to_user32

Among the existing architecture specific versions of
copy_siginfo_to_user32 there are several different implementation
problems.  Some architectures fail to handle all of the cases in in
the siginfo union.  Some architectures perform a blind copy of the
siginfo union when the si_code is negative.  A blind copy suggests the
data is expected to be in 32bit siginfo format, which means that
receiving such a signal via signalfd won't work, or that the data is
in 64bit siginfo and the code is copying nonsense to userspace.

Create a single instance of copy_siginfo_to_user32 that all of the
architectures can share, and teach it to handle all of the cases in
the siginfo union correctly, with the assumption that siginfo is
stored internally to the kernel is 64bit siginfo format.

A special case is made for x86 x32 format.  This is needed as presence
of both x32 and ia32 on x86_64 results in two different 32bit signal
formats.  By allowing this small special case there winds up being
exactly one code base that needs to be maintained between all of the
architectures.  Vastly increasing the testing base and the chances of
finding bugs.

As the x86 copy of copy_siginfo_to_user32 the call of the x86
signal_compat_build_tests were moved into sigaction_compat_abi, so
that they will keep running.

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

3 files changed, 6 insertions, 100 deletions

diff --git a/arch/x86/include/asm/compat.h b/arch/x86/include/asm/compat.h
index 0b76fc91f672..e1c8dab86670 100644
--- a/arch/x86/include/asm/compat.h
+++ b/arch/x86/include/asm/compat.h
@@ -249,4 +249,8 @@ static inline bool in_compat_syscall(void)
 }
 #define in_compat_syscall in_compat_syscall	/* override the generic impl */
 
+struct compat_siginfo;
+int __copy_siginfo_to_user32(struct compat_siginfo __user *to,
+		const siginfo_t *from, bool x32_ABI);
+
 #endif /* _ASM_X86_COMPAT_H */
diff --git a/arch/x86/include/asm/fpu/signal.h b/arch/x86/include/asm/fpu/signal.h
index 4df2754ef380..44bbc39a57b3 100644
--- a/arch/x86/include/asm/fpu/signal.h
+++ b/arch/x86/include/asm/fpu/signal.h
@@ -20,12 +20,6 @@ int ia32_setup_frame(int sig, struct ksignal *ksig,
 # define ia32_setup_rt_frame	__setup_rt_frame
 #endif
 
-#ifdef CONFIG_COMPAT
-int __copy_siginfo_to_user32(compat_siginfo_t __user *to,
-		const siginfo_t *from, bool x32_ABI);
-#endif
-
-
 extern void convert_from_fxsr(struct user_i387_ia32_struct *env,
 			      struct task_struct *tsk);
 extern void convert_to_fxsr(struct task_struct *tsk,
diff --git a/arch/x86/kernel/signal_compat.c b/arch/x86/kernel/signal_compat.c
index 59148de2d83f..ac057f9b0763 100644
--- a/arch/x86/kernel/signal_compat.c
+++ b/arch/x86/kernel/signal_compat.c
@@ -98,6 +98,8 @@ static inline void signal_compat_build_tests(void)
 
 void sigaction_compat_abi(struct k_sigaction *act, struct k_sigaction *oact)
 {
+	signal_compat_build_tests();
+
 	/* Don't leak in-kernel non-uapi flags to user-space */
 	if (oact)
 		oact->sa.sa_flags &= ~(SA_IA32_ABI | SA_X32_ABI);
@@ -113,97 +115,3 @@ void sigaction_compat_abi(struct k_sigaction *act, struct k_sigaction *oact)
 	if (in_x32_syscall())
 		act->sa.sa_flags |= SA_X32_ABI;
 }
-
-int __copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from,
-		bool x32_ABI)
-{
-	int err = 0;
-
-	signal_compat_build_tests();
-
-	if (!access_ok(VERIFY_WRITE, to, sizeof(compat_siginfo_t)))
-		return -EFAULT;
-
-	put_user_try {
-		/* If you change siginfo_t structure, please make sure that
-		   this code is fixed accordingly.
-		   It should never copy any pad contained in the structure
-		   to avoid security leaks, but must copy the generic
-		   3 ints plus the relevant union member.  */
-		put_user_ex(from->si_signo, &to->si_signo);
-		put_user_ex(from->si_errno, &to->si_errno);
-		put_user_ex(from->si_code, &to->si_code);
-
-		if (from->si_code < 0) {
-			put_user_ex(from->si_pid, &to->si_pid);
-			put_user_ex(from->si_uid, &to->si_uid);
-			put_user_ex(ptr_to_compat(from->si_ptr), &to->si_ptr);
-		} else {
-			/*
-			 * First 32bits of unions are always present:
-			 * si_pid === si_band === si_tid === si_addr(LS half)
-			 */
-			put_user_ex(from->_sifields._pad[0],
-					  &to->_sifields._pad[0]);
-			switch (siginfo_layout(from->si_signo, from->si_code)) {
-			case SIL_FAULT:
-				if (from->si_signo == SIGBUS &&
-				    (from->si_code == BUS_MCEERR_AR ||
-				     from->si_code == BUS_MCEERR_AO))
-					put_user_ex(from->si_addr_lsb, &to->si_addr_lsb);
-
-				if (from->si_signo == SIGSEGV) {
-					if (from->si_code == SEGV_BNDERR) {
-						compat_uptr_t lower = (unsigned long)from->si_lower;
-						compat_uptr_t upper = (unsigned long)from->si_upper;
-						put_user_ex(lower, &to->si_lower);
-						put_user_ex(upper, &to->si_upper);
-					}
-					if (from->si_code == SEGV_PKUERR)
-						put_user_ex(from->si_pkey, &to->si_pkey);
-				}
-				break;
-			case SIL_SYS:
-				put_user_ex(from->si_syscall, &to->si_syscall);
-				put_user_ex(from->si_arch, &to->si_arch);
-				break;
-			case SIL_CHLD:
-				if (!x32_ABI) {
-					put_user_ex(from->si_utime, &to->si_utime);
-					put_user_ex(from->si_stime, &to->si_stime);
-#ifdef CONFIG_X86_X32_ABI
-				} else {
-					put_user_ex(from->si_utime, &to->_sifields._sigchld_x32._utime);
-					put_user_ex(from->si_stime, &to->_sifields._sigchld_x32._stime);
-#endif
-				}
-				put_user_ex(from->si_status, &to->si_status);
-				/* FALL THROUGH */
-			case SIL_KILL:
-				put_user_ex(from->si_uid, &to->si_uid);
-				break;
-			case SIL_POLL:
-				put_user_ex(from->si_fd, &to->si_fd);
-				break;
-			case SIL_TIMER:
-				put_user_ex(from->si_overrun, &to->si_overrun);
-				put_user_ex(ptr_to_compat(from->si_ptr),
-					    &to->si_ptr);
-				break;
-			case SIL_RT:
-				put_user_ex(from->si_uid, &to->si_uid);
-				put_user_ex(from->si_int, &to->si_int);
-				break;
-			}
-		}
-	} put_user_catch(err);
-
-	return err;
-}
-
-/* from syscall's path, where we know the ABI */
-int copy_siginfo_to_user32(compat_siginfo_t __user *to, const siginfo_t *from)
-{
-	return __copy_siginfo_to_user32(to, from, in_x32_syscall());
-}
-