Audit: push audit success and retcode into arch ptrace.h

The audit system previously expected arches calling to audit_syscall_exit to
supply as arguments if the syscall was a success and what the return code was.
Audit also provides a helper AUDITSC_RESULT which was supposed to simplify things
by converting from negative retcodes to an audit internal magic value stating
success or failure.  This helper was wrong and could indicate that a valid
pointer returned to userspace was a failed syscall.  The fix is to fix the
layering foolishness.  We now pass audit_syscall_exit a struct pt_reg and it
in turns calls back into arch code to collect the return value and to
determine if the syscall was a success or failure.  We also define a generic
is_syscall_success() macro which determines success/failure based on if the
value is < -MAX_ERRNO.  This works for arches like x86 which do not use a
separate mechanism to indicate syscall failure.

We make both the is_syscall_success() and regs_return_value() static inlines
instead of macros.  The reason is because the audit function must take a void*
for the regs.  (uml calls theirs struct uml_pt_regs instead of just struct
pt_regs so audit_syscall_exit can't take a struct pt_regs).  Since the audit
function takes a void* we need to use static inlines to cast it back to the
arch correct structure to dereference it.

The other major change is that on some arches, like ia64, MIPS and ppc, we
change regs_return_value() to give us the negative value on syscall failure.
THE only other user of this macro, kretprobe_example.c, won't notice and it
makes the value signed consistently for the audit functions across all archs.

In arch/sh/kernel/ptrace_64.c I see that we were using regs[9] in the old
audit code as the return value.  But the ptrace_64.h code defined the macro
regs_return_value() as regs[3].  I have no idea which one is correct, but this
patch now uses the regs_return_value() function, so it now uses regs[3].

For powerpc we previously used regs->result but now use the
regs_return_value() function which uses regs->gprs[3].  regs->gprs[3] is
always positive so the regs_return_value(), much like ia64 makes it negative
before calling the audit code when appropriate.

Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: H. Peter Anvin <hpa@zytor.com> [for x86 portion]
Acked-by: Tony Luck <tony.luck@intel.com> [for ia64]
Acked-by: Richard Weinberger <richard@nod.at> [for uml]
Acked-by: David S. Miller <davem@davemloft.net> [for sparc]
Acked-by: Ralf Baechle <ralf@linux-mips.org> [for mips]
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> [for ppc]

2 files changed, 24 insertions, 8 deletions

diff --git a/include/linux/audit.h b/include/linux/audit.h
index 6e1c533..3d65e4b 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -26,6 +26,7 @@
 
 #include <linux/types.h>
 #include <linux/elf-em.h>
+#include <linux/ptrace.h>
 
 /* The netlink messages for the audit system is divided into blocks:
  * 1000 - 1099 are for commanding the audit system
@@ -408,10 +409,6 @@ struct audit_field {
 	void				*lsm_rule;
 };
 
-#define AUDITSC_INVALID 0
-#define AUDITSC_SUCCESS 1
-#define AUDITSC_FAILURE 2
-#define AUDITSC_RESULT(x) ( ((long)(x))<0?AUDITSC_FAILURE:AUDITSC_SUCCESS )
 extern int __init audit_register_class(int class, unsigned *list);
 extern int audit_classify_syscall(int abi, unsigned syscall);
 extern int audit_classify_arch(int arch);
@@ -424,7 +421,7 @@ extern void audit_free(struct task_struct *task);
 extern void audit_syscall_entry(int arch,
 				int major, unsigned long a0, unsigned long a1,
 				unsigned long a2, unsigned long a3);
-extern void audit_syscall_exit(int failed, long return_code);
+extern void __audit_syscall_exit(int ret_success, long ret_value);
 extern void __audit_getname(const char *name);
 extern void audit_putname(const char *name);
 extern void __audit_inode(const char *name, const struct dentry *dentry);
@@ -438,6 +435,15 @@ static inline int audit_dummy_context(void)
 	void *p = current->audit_context;
 	return !p || *(int *)p;
 }
+static inline void audit_syscall_exit(void *pt_regs)
+{
+	if (unlikely(current->audit_context)) {
+		int success = is_syscall_success(pt_regs);
+		int return_code = regs_return_value(pt_regs);
+
+		__audit_syscall_exit(success, return_code);
+	}
+}
 static inline void audit_getname(const char *name)
 {
 	if (unlikely(!audit_dummy_context()))
@@ -551,12 +557,12 @@ static inline void audit_mmap_fd(int fd, int flags)
 
 extern int audit_n_rules;
 extern int audit_signals;
-#else
+#else /* CONFIG_AUDITSYSCALL */
 #define audit_finish_fork(t)
 #define audit_alloc(t) ({ 0; })
 #define audit_free(t) do { ; } while (0)
 #define audit_syscall_entry(ta,a,b,c,d,e) do { ; } while (0)
-#define audit_syscall_exit(f,r) do { ; } while (0)
+#define audit_syscall_exit(r) do { ; } while (0)
 #define audit_dummy_context() 1
 #define audit_getname(n) do { ; } while (0)
 #define audit_putname(n) do { ; } while (0)
@@ -587,7 +593,7 @@ extern int audit_signals;
 #define audit_ptrace(t) ((void)0)
 #define audit_n_rules 0
 #define audit_signals 0
-#endif
+#endif /* CONFIG_AUDITSYSCALL */
 
 #ifdef CONFIG_AUDIT
 /* These are defined in audit.c */
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index 800f113..dd4cefa 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -112,6 +112,7 @@
 
 #include <linux/compiler.h>		/* For unlikely.  */
 #include <linux/sched.h>		/* For struct task_struct.  */
+#include <linux/err.h>			/* for IS_ERR_VALUE */
 
 
 extern long arch_ptrace(struct task_struct *child, long request,
@@ -265,6 +266,15 @@ static inline void ptrace_release_task(struct task_struct *task)
 #define force_successful_syscall_return() do { } while (0)
 #endif
 
+#ifndef is_syscall_success
+/*
+ * On most systems we can tell if a syscall is a success based on if the retval
+ * is an error value.  On some systems like ia64 and powerpc they have different
+ * indicators of success/failure and must define their own.
+ */
+#define is_syscall_success(regs) (!IS_ERR_VALUE((unsigned long)(regs_return_value(regs))))
+#endif
+
 /*
  * <asm/ptrace.h> should define the following things inside #ifdef __KERNEL__.
  *