tracehook: exec

This moves all the ptrace hooks related to exec into tracehook.h inlines.

This also lifts the calls for tracing out of the binfmt load_binary hooks
into search_binary_handler() after it calls into the binfmt module.  This
change has no effect, since all the binfmt modules' load_binary functions
did the call at the end on success, and now search_binary_handler() does
it immediately after return if successful.  We consolidate the repeated
code, and binfmt modules no longer need to import ptrace_notify().

Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Reviewed-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

8 files changed, 50 insertions, 38 deletions

diff --git a/arch/x86/ia32/ia32_aout.c b/arch/x86/ia32/ia32_aout.c
index 58cccb6483b0..a0e1dbe67dc1 100644
--- a/arch/x86/ia32/ia32_aout.c
+++ b/arch/x86/ia32/ia32_aout.c
@@ -441,12 +441,6 @@ beyond_if:
         regs->r8 = regs->r9 = regs->r10 = regs->r11 =
         regs->r12 = regs->r13 = regs->r14 = regs->r15 = 0;
         set_fs(USER_DS);
-        if (unlikely(current->ptrace & PT_PTRACED)) {
-                if (current->ptrace & PT_TRACE_EXEC)
-                        ptrace_notify((PTRACE_EVENT_EXEC << 8) | SIGTRAP);
-                else
-                        send_sig(SIGTRAP, current, 0);
-        }
         return 0;
 }
 
diff --git a/fs/binfmt_aout.c b/fs/binfmt_aout.c
index ba4cddb92f1d..204cfd1d7676 100644
--- a/fs/binfmt_aout.c
+++ b/fs/binfmt_aout.c
@@ -444,12 +444,6 @@ beyond_if:
         regs->gp = ex.a_gpvalue;
 #endif
         start_thread(regs, ex.a_entry, current->mm->start_stack);
-        if (unlikely(current->ptrace & PT_PTRACED)) {
-                if (current->ptrace & PT_TRACE_EXEC)
-                        ptrace_notify ((PTRACE_EVENT_EXEC << 8) | SIGTRAP);
-                else
-                        send_sig(SIGTRAP, current, 0);
-        }
         return 0;
 }
 
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 3b6ff854d983..655ed8d30a86 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1003,12 +1003,6 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs)
 #endif
 
         start_thread(regs, elf_entry, bprm->p);
-        if (unlikely(current->ptrace & PT_PTRACED)) {
-                if (current->ptrace & PT_TRACE_EXEC)
-                        ptrace_notify ((PTRACE_EVENT_EXEC << 8) | SIGTRAP);
-                else
-                        send_sig(SIGTRAP, current, 0);
-        }
         retval = 0;
 out:
         kfree(loc);
diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index 1b59b1edf26d..fdeadab2f18b 100644
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -433,13 +433,6 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm,
         entryaddr = interp_params.entry_addr ?: exec_params.entry_addr;
         start_thread(regs, entryaddr, current->mm->start_stack);
 
-        if (unlikely(current->ptrace & PT_PTRACED)) {
-                if (current->ptrace & PT_TRACE_EXEC)
-                        ptrace_notify((PTRACE_EVENT_EXEC << 8) | SIGTRAP);
-                else
-                        send_sig(SIGTRAP, current, 0);
-        }
-
         retval = 0;
 
 error:
diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c
index 2cb1acda3a82..56372ecf1690 100644
--- a/fs/binfmt_flat.c
+++ b/fs/binfmt_flat.c
@@ -920,9 +920,6 @@ static int load_flat_binary(struct linux_binprm * bprm, struct pt_regs * regs)
         
         start_thread(regs, start_addr, current->mm->start_stack);
 
-        if (current->ptrace & PT_PTRACED)
-                send_sig(SIGTRAP, current, 0);
-
         return 0;
 }
 
diff --git a/fs/binfmt_som.c b/fs/binfmt_som.c
index fdc36bfd6a7b..68be580ba289 100644
--- a/fs/binfmt_som.c
+++ b/fs/binfmt_som.c
@@ -274,8 +274,6 @@ load_som_binary(struct linux_binprm * bprm, struct pt_regs * regs)
         map_hpux_gateway_page(current,current->mm);
 
         start_thread_som(regs, som_entry, bprm->p);
-        if (current->ptrace & PT_PTRACED)
-                send_sig(SIGTRAP, current, 0);
         return 0;
 
         /* error cleanup */
diff --git a/fs/exec.c b/fs/exec.c
index 5e559013e303..b8792a131533 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -42,13 +42,13 @@
 #include <linux/module.h>
 #include <linux/namei.h>
 #include <linux/proc_fs.h>
-#include <linux/ptrace.h>
 #include <linux/mount.h>
 #include <linux/security.h>
 #include <linux/syscalls.h>
 #include <linux/tsacct_kern.h>
 #include <linux/cn_proc.h>
 #include <linux/audit.h>
+#include <linux/tracehook.h>
 
 #include <asm/uaccess.h>
 #include <asm/mmu_context.h>
@@ -1071,13 +1071,8 @@ EXPORT_SYMBOL(prepare_binprm);
 
 static int unsafe_exec(struct task_struct *p)
 {
-        int unsafe = 0;
-        if (p->ptrace & PT_PTRACED) {
-                if (p->ptrace & PT_PTRACE_CAP)
-                        unsafe |= LSM_UNSAFE_PTRACE_CAP;
-                else
-                        unsafe |= LSM_UNSAFE_PTRACE;
-        }
+        int unsafe = tracehook_unsafe_exec(p);
+
         if (atomic_read(&p->fs->count) > 1 ||
             atomic_read(&p->files->count) > 1 ||
             atomic_read(&p->sighand->count) > 1)
@@ -1214,6 +1209,7 @@ int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)
                         read_unlock(&binfmt_lock);
                         retval = fn(bprm, regs);
                         if (retval >= 0) {
+                                tracehook_report_exec(fmt, bprm, regs);
                                 put_binfmt(fmt);
                                 allow_write_access(bprm->file);
                                 if (bprm->file)
diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
index bea0f3eeff54..6276353709c1 100644
--- a/include/linux/tracehook.h
+++ b/include/linux/tracehook.h
@@ -48,5 +48,51 @@
 
 #include <linux/sched.h>
 #include <linux/ptrace.h>
+#include <linux/security.h>
+struct linux_binprm;
+
+/**
+ * tracehook_unsafe_exec - check for exec declared unsafe due to tracing
+ * @task:               current task doing exec
+ *
+ * Return %LSM_UNSAFE_* bits applied to an exec because of tracing.
+ *
+ * Called with task_lock() held on @task.
+ */
+static inline int tracehook_unsafe_exec(struct task_struct *task)
+{
+        int unsafe = 0;
+        int ptrace = task_ptrace(task);
+        if (ptrace & PT_PTRACED) {
+                if (ptrace & PT_PTRACE_CAP)
+                        unsafe |= LSM_UNSAFE_PTRACE_CAP;
+                else
+                        unsafe |= LSM_UNSAFE_PTRACE;
+        }
+        return unsafe;
+}
+
+/**
+ * tracehook_report_exec - a successful exec was completed
+ * @fmt:                &struct linux_binfmt that performed the exec
+ * @bprm:               &struct linux_binprm containing exec details
+ * @regs:               user-mode register state
+ *
+ * An exec just completed, we are shortly going to return to user mode.
+ * The freshly initialized register state can be seen and changed in @regs.
+ * The name, file and other pointers in @bprm are still on hand to be
+ * inspected, but will be freed as soon as this returns.
+ *
+ * Called with no locks, but with some kernel resources held live
+ * and a reference on @fmt->module.
+ */
+static inline void tracehook_report_exec(struct linux_binfmt *fmt,
+                                         struct linux_binprm *bprm,
+                                         struct pt_regs *regs)
+{
+        if (!ptrace_event(PT_TRACE_EXEC, PTRACE_EVENT_EXEC, 0) &&
+            unlikely(task_ptrace(current) & PT_PTRACED))
+                send_sig(SIGTRAP, current, 0);
+}
 
 #endif  /* <linux/tracehook.h> */