[PATCH] use ptrace_get_task_struct in various places

The ptrace_get_task_struct() helper that I added as part of the ptrace
consolidation is useful in variety of places that currently opencode it.
Switch them to the common helpers.

Add a ptrace_traceme() helper that needs to be explicitly called, and simplify
the ptrace_get_task_struct() interface.  We don't need the request argument
now, and we return the task_struct directly, using ERR_PTR() for error
returns.  It's a bit more code in the callers, but we have two sane routines
that do one thing well now.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

12 files changed, 105 insertions, 241 deletions

diff --git a/arch/alpha/kernel/ptrace.c b/arch/alpha/kernel/ptrace.c
index bbd37536d14e..9969d212e94d 100644
--- a/arch/alpha/kernel/ptrace.c
+++ b/arch/alpha/kernel/ptrace.c
@@ -265,30 +265,16 @@ do_sys_ptrace(long request, long pid, long addr, long data,
         lock_kernel();
         DBG(DBG_MEM, ("request=%ld pid=%ld addr=0x%lx data=0x%lx\n",
                       request, pid, addr, data));
-        ret = -EPERM;
         if (request == PTRACE_TRACEME) {
-                /* are we already being traced? */
-                if (current->ptrace & PT_PTRACED)
-                        goto out_notsk;
-                ret = security_ptrace(current->parent, current);
-                if (ret)
-                        goto out_notsk;
-                /* set the ptrace bit in the process ptrace flags. */
-                current->ptrace |= PT_PTRACED;
-                ret = 0;
+                ret = ptrace_traceme();
                 goto out_notsk;
         }
-        if (pid == 1)           /* you may not mess with init */
-                goto out_notsk;
 
-        ret = -ESRCH;
-        read_lock(&tasklist_lock);
-        child = find_task_by_pid(pid);
-        if (child)
-                get_task_struct(child);
-        read_unlock(&tasklist_lock);
-        if (!child)
+        child = ptrace_get_task_struct(pid);
+        if (IS_ERR(child)) {
+                ret = PTR_ERR(child);
                 goto out_notsk;
+        }
 
         if (request == PTRACE_ATTACH) {
                 ret = ptrace_attach(child);
diff --git a/arch/ia64/ia32/sys_ia32.c b/arch/ia64/ia32/sys_ia32.c
index dc282710421a..9f8e8d558873 100644
--- a/arch/ia64/ia32/sys_ia32.c
+++ b/arch/ia64/ia32/sys_ia32.c
@@ -1761,21 +1761,15 @@ sys32_ptrace (int request, pid_t pid, unsigned int addr, unsigned int data)
 
         lock_kernel();
         if (request == PTRACE_TRACEME) {
-                ret = sys_ptrace(request, pid, addr, data);
+                ret = ptrace_traceme();
                 goto out;
         }
 
-        ret = -ESRCH;
-        read_lock(&tasklist_lock);
-        child = find_task_by_pid(pid);
-        if (child)
-                get_task_struct(child);
-        read_unlock(&tasklist_lock);
-        if (!child)
+        child = ptrace_get_task_struct(pid);
+        if (IS_ERR(child)) {
+                ret = PTR_ERR(child);
                 goto out;
-        ret = -EPERM;
-        if (pid == 1)           /* no messing around with init! */
-                goto out_tsk;
+        }
 
         if (request == PTRACE_ATTACH) {
                 ret = sys_ptrace(request, pid, addr, data);
diff --git a/arch/ia64/kernel/ptrace.c b/arch/ia64/kernel/ptrace.c
index 4b19d0410632..8d88eeea02d1 100644
--- a/arch/ia64/kernel/ptrace.c
+++ b/arch/ia64/kernel/ptrace.c
@@ -1422,14 +1422,7 @@ sys_ptrace (long request, pid_t pid, unsigned long addr, unsigned long data)
         lock_kernel();
         ret = -EPERM;
         if (request == PTRACE_TRACEME) {
-                /* are we already being traced? */
-                if (current->ptrace & PT_PTRACED)
-                        goto out;
-                ret = security_ptrace(current->parent, current);
-                if (ret)
-                        goto out;
-                current->ptrace |= PT_PTRACED;
-                ret = 0;
+                ret = ptrace_traceme();
                 goto out;
         }
 
diff --git a/arch/m32r/kernel/ptrace.c b/arch/m32r/kernel/ptrace.c
index 078d2a0e71c2..9b75caaf5cec 100644
--- a/arch/m32r/kernel/ptrace.c
+++ b/arch/m32r/kernel/ptrace.c
@@ -762,28 +762,16 @@ asmlinkage long sys_ptrace(long request, long pid, long addr, long data)
         int ret;
 
         lock_kernel();
-        ret = -EPERM;
         if (request == PTRACE_TRACEME) {
-                /* are we already being traced? */
-                if (current->ptrace & PT_PTRACED)
-                        goto out;
-                /* set the ptrace bit in the process flags. */
-                current->ptrace |= PT_PTRACED;
-                ret = 0;
+                ret = ptrace_traceme();
                 goto out;
         }
-        ret = -ESRCH;
-        read_lock(&tasklist_lock);
-        child = find_task_by_pid(pid);
-        if (child)
-                get_task_struct(child);
-        read_unlock(&tasklist_lock);
-        if (!child)
-                goto out;
 
-        ret = -EPERM;
-        if (pid == 1)           /* you may not mess with init */
+        child = ptrace_get_task_struct(pid);
+        if (IS_ERR(child)) {
+                ret = PTR_ERR(child);
                 goto out;
+        }
 
         if (request == PTRACE_ATTACH) {
                 ret = ptrace_attach(child);
diff --git a/arch/mips/kernel/ptrace32.c b/arch/mips/kernel/ptrace32.c
index 9a9b04972132..7e55457a491f 100644
--- a/arch/mips/kernel/ptrace32.c
+++ b/arch/mips/kernel/ptrace32.c
@@ -57,30 +57,16 @@ asmlinkage int sys32_ptrace(int request, int pid, int addr, int data)
                (unsigned long) data);
 #endif
         lock_kernel();
-        ret = -EPERM;
         if (request == PTRACE_TRACEME) {
-                /* are we already being traced? */
-                if (current->ptrace & PT_PTRACED)
-                        goto out;
-                if ((ret = security_ptrace(current->parent, current)))
-                        goto out;
-                /* set the ptrace bit in the process flags. */
-                current->ptrace |= PT_PTRACED;
-                ret = 0;
+                ret = ptrace_traceme();
                 goto out;
         }
-        ret = -ESRCH;
-        read_lock(&tasklist_lock);
-        child = find_task_by_pid(pid);
-        if (child)
-                get_task_struct(child);
-        read_unlock(&tasklist_lock);
-        if (!child)
-                goto out;
 
-        ret = -EPERM;
-        if (pid == 1)           /* you may not mess with init */
-                goto out_tsk;
+        child = ptrace_get_task_struct(pid);
+        if (IS_ERR(child)) {
+                ret = PTR_ERR(child);
+                goto out;
+        }
 
         if (request == PTRACE_ATTACH) {
                 ret = ptrace_attach(child);
diff --git a/arch/powerpc/kernel/ptrace32.c b/arch/powerpc/kernel/ptrace32.c
index 61762640b877..826ee3d056de 100644
--- a/arch/powerpc/kernel/ptrace32.c
+++ b/arch/powerpc/kernel/ptrace32.c
@@ -45,33 +45,19 @@ long compat_sys_ptrace(int request, int pid, unsigned long addr,
                        unsigned long data)
 {
         struct task_struct *child;
-        int ret = -EPERM;
+        int ret;
 
         lock_kernel();
         if (request == PTRACE_TRACEME) {
-                /* are we already being traced? */
-                if (current->ptrace & PT_PTRACED)
-                        goto out;
-                ret = security_ptrace(current->parent, current);
-                if (ret)
-                        goto out;
-                /* set the ptrace bit in the process flags. */
-                current->ptrace |= PT_PTRACED;
-                ret = 0;
+                ret = ptrace_traceme();
                 goto out;
         }
-        ret = -ESRCH;
-        read_lock(&tasklist_lock);
-        child = find_task_by_pid(pid);
-        if (child)
-                get_task_struct(child);
-        read_unlock(&tasklist_lock);
-        if (!child)
-                goto out;
 
-        ret = -EPERM;
-        if (pid == 1)           /* you may not mess with init */
-                goto out_tsk;
+        child = ptrace_get_task_struct(pid);
+        if (IS_ERR(child)) {
+                ret = PTR_ERR(child);
+                goto out;
+        }
 
         if (request == PTRACE_ATTACH) {
                 ret = ptrace_attach(child);
diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c
index 8ecda6d66de4..cc02232aa96e 100644
--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -712,35 +712,18 @@ sys_ptrace(long request, long pid, long addr, long data)
         int ret;
 
         lock_kernel();
-
         if (request == PTRACE_TRACEME) {
-                /* are we already being traced? */
-                ret = -EPERM;
-                if (current->ptrace & PT_PTRACED)
-                        goto out;
-                ret = security_ptrace(current->parent, current);
-                if (ret)
-                        goto out;
-                /* set the ptrace bit in the process flags. */
-                current->ptrace |= PT_PTRACED;
-                goto out;
+                 ret = ptrace_traceme();
+                 goto out;
         }
 
-        ret = -EPERM;
-        if (pid == 1)           /* you may not mess with init */
-                goto out;
-
-        ret = -ESRCH;
-        read_lock(&tasklist_lock);
-        child = find_task_by_pid(pid);
-        if (child)
-                get_task_struct(child);
-        read_unlock(&tasklist_lock);
-        if (!child)
+        child = ptrace_get_task_struct(pid);
+        if (IS_ERR(child)) {
+                ret = PTR_ERR(child);
                 goto out;
+        }
 
         ret = do_ptrace(child, request, addr, data);
-
         put_task_struct(child);
 out:
         unlock_kernel();
diff --git a/arch/sparc/kernel/ptrace.c b/arch/sparc/kernel/ptrace.c
index 475c4c13462c..fc470c0e9dc6 100644
--- a/arch/sparc/kernel/ptrace.c
+++ b/arch/sparc/kernel/ptrace.c
@@ -286,40 +286,17 @@ asmlinkage void do_ptrace(struct pt_regs *regs)
                                s, (int) request, (int) pid, addr, data, addr2);
         }
 #endif
-        if (request == PTRACE_TRACEME) {
-                int my_ret;
-
-                /* are we already being traced? */
-                if (current->ptrace & PT_PTRACED) {
-                        pt_error_return(regs, EPERM);
-                        goto out;
-                }
-                my_ret = security_ptrace(current->parent, current);
-                if (my_ret) {
-                        pt_error_return(regs, -my_ret);
-                        goto out;
-                }
 
-                /* set the ptrace bit in the process flags. */
-                current->ptrace |= PT_PTRACED;
+        if (request == PTRACE_TRACEME) {
+                ret = ptrace_traceme();
                 pt_succ_return(regs, 0);
                 goto out;
         }
-#ifndef ALLOW_INIT_TRACING
-        if (pid == 1) {
-                /* Can't dork with init. */
-                pt_error_return(regs, EPERM);
-                goto out;
-        }
-#endif
-        read_lock(&tasklist_lock);
-        child = find_task_by_pid(pid);
-        if (child)
-                get_task_struct(child);
-        read_unlock(&tasklist_lock);
 
-        if (!child) {
-                pt_error_return(regs, ESRCH);
+        child = ptrace_get_task_struct(pid);
+        if (IS_ERR(child)) {
+                ret = PTR_ERR(child);
+                pt_error_return(regs, -ret);
                 goto out;
         }
 
diff --git a/arch/sparc64/kernel/ptrace.c b/arch/sparc64/kernel/ptrace.c
index 774ecbb8a031..84d3df2264cb 100644
--- a/arch/sparc64/kernel/ptrace.c
+++ b/arch/sparc64/kernel/ptrace.c
@@ -198,39 +198,15 @@ asmlinkage void do_ptrace(struct pt_regs *regs)
         }
 #endif
         if (request == PTRACE_TRACEME) {
-                int ret;
-
-                /* are we already being traced? */
-                if (current->ptrace & PT_PTRACED) {
-                        pt_error_return(regs, EPERM);
-                        goto out;
-                }
-                ret = security_ptrace(current->parent, current);
-                if (ret) {
-                        pt_error_return(regs, -ret);
-                        goto out;
-                }
-
-                /* set the ptrace bit in the process flags. */
-                current->ptrace |= PT_PTRACED;
+                ret = ptrace_traceme();
                 pt_succ_return(regs, 0);
                 goto out;
         }
-#ifndef ALLOW_INIT_TRACING
-        if (pid == 1) {
-                /* Can't dork with init. */
-                pt_error_return(regs, EPERM);
-                goto out;
-        }
-#endif
-        read_lock(&tasklist_lock);
-        child = find_task_by_pid(pid);
-        if (child)
-                get_task_struct(child);
-        read_unlock(&tasklist_lock);
 
-        if (!child) {
-                pt_error_return(regs, ESRCH);
+        child = ptrace_get_task_struct(pid);
+        if (IS_ERR(child)) {
+                ret = PTR_ERR(child);
+                pt_error_return(regs, -ret);
                 goto out;
         }
 
diff --git a/arch/x86_64/ia32/ptrace32.c b/arch/x86_64/ia32/ptrace32.c
index 2a925e2af390..5f4cdfa56901 100644
--- a/arch/x86_64/ia32/ptrace32.c
+++ b/arch/x86_64/ia32/ptrace32.c
@@ -196,36 +196,6 @@ static int getreg32(struct task_struct *child, unsigned regno, u32 *val)
 
 #undef R32
 
-static struct task_struct *find_target(int request, int pid, int *err)
-{ 
-        struct task_struct *child;
-
-        *err = -EPERM; 
-        if (pid == 1)
-                return NULL; 
-
-        *err = -ESRCH;
-        read_lock(&tasklist_lock);
-        child = find_task_by_pid(pid);
-        if (child)
-                get_task_struct(child);
-        read_unlock(&tasklist_lock);
-        if (child) { 
-                *err = -EPERM;
-                if (child->pid == 1) 
-                        goto out;
-                *err = ptrace_check_attach(child, request == PTRACE_KILL); 
-                if (*err < 0) 
-                        goto out;
-                return child; 
-        } 
- out:
-        if (child)
-        put_task_struct(child);
-        return NULL; 
-        
-} 
-
 asmlinkage long sys32_ptrace(long request, u32 pid, u32 addr, u32 data)
 {
         struct task_struct *child;
@@ -254,9 +224,16 @@ asmlinkage long sys32_ptrace(long request, u32 pid, u32 addr, u32 data)
                 break;
         } 
 
-        child = find_target(request, pid, &ret);
-        if (!child)
-                return ret;
+        if (request == PTRACE_TRACEME)
+                return ptrace_traceme();
+
+        child = ptrace_get_task_struct(pid);
+        if (IS_ERR(child))
+                return PTR_ERR(child);
+
+        ret = ptrace_check_attach(child, request == PTRACE_KILL);
+        if (ret < 0)
+                goto out;
 
         childregs = (struct pt_regs *)(child->thread.rsp0 - sizeof(struct pt_regs)); 
 
@@ -373,6 +350,7 @@ asmlinkage long sys32_ptrace(long request, u32 pid, u32 addr, u32 data)
                 break;
         }
 
+ out:
         put_task_struct(child);
         return ret;
 }
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index b2b3dba1298d..864791996b5f 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -80,6 +80,8 @@
 
 
 extern long arch_ptrace(struct task_struct *child, long request, long addr, long data);
+extern struct task_struct *ptrace_get_task_struct(pid_t pid);
+extern int ptrace_traceme(void);
 extern int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len);
 extern int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len);
 extern int ptrace_attach(struct task_struct *tsk);
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 656476eedb1b..cceaf09ac413 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -408,54 +408,62 @@ int ptrace_request(struct task_struct *child, long request,
         return ret;
 }
 
-#ifndef __ARCH_SYS_PTRACE
-static int ptrace_get_task_struct(long request, long pid,
-                struct task_struct **childp)
+/**
+ * ptrace_traceme  --  helper for PTRACE_TRACEME
+ *
+ * Performs checks and sets PT_PTRACED.
+ * Should be used by all ptrace implementations for PTRACE_TRACEME.
+ */
+int ptrace_traceme(void)
 {
-        struct task_struct *child;
         int ret;
 
         /*
-         * Callers use child == NULL as an indication to exit early even
-         * when the return value is 0, so make sure it is non-NULL here.
+         * Are we already being traced?
+         */
+        if (current->ptrace & PT_PTRACED)
+                return -EPERM;
+        ret = security_ptrace(current->parent, current);
+        if (ret)
+                return -EPERM;
+        /*
+         * Set the ptrace bit in the process ptrace flags.
          */
-        *childp = NULL;
+        current->ptrace |= PT_PTRACED;
+        return 0;
+}
 
-        if (request == PTRACE_TRACEME) {
-                /*
-                 * Are we already being traced?
-                 */
-                if (current->ptrace & PT_PTRACED)
-                        return -EPERM;
-                ret = security_ptrace(current->parent, current);
-                if (ret)
-                        return -EPERM;
-                /*
-                 * Set the ptrace bit in the process ptrace flags.
-                 */
-                current->ptrace |= PT_PTRACED;
-                return 0;
-        }
+/**
+ * ptrace_get_task_struct  --  grab a task struct reference for ptrace
+ * @pid:       process id to grab a task_struct reference of
+ *
+ * This function is a helper for ptrace implementations.  It checks
+ * permissions and then grabs a task struct for use of the actual
+ * ptrace implementation.
+ *
+ * Returns the task_struct for @pid or an ERR_PTR() on failure.
+ */
+struct task_struct *ptrace_get_task_struct(pid_t pid)
+{
+        struct task_struct *child;
 
         /*
-         * You may not mess with init
+         * Tracing init is not allowed.
          */
         if (pid == 1)
-                return -EPERM;
+                return ERR_PTR(-EPERM);
 
-        ret = -ESRCH;
         read_lock(&tasklist_lock);
         child = find_task_by_pid(pid);
         if (child)
                 get_task_struct(child);
         read_unlock(&tasklist_lock);
         if (!child)
-                return -ESRCH;
-
-        *childp = child;
-        return 0;
+                return ERR_PTR(-ESRCH);
+        return child;
 }
 
+#ifndef __ARCH_SYS_PTRACE
 asmlinkage long sys_ptrace(long request, long pid, long addr, long data)
 {
         struct task_struct *child;
@@ -465,9 +473,16 @@ asmlinkage long sys_ptrace(long request, long pid, long addr, long data)
          * This lock_kernel fixes a subtle race with suid exec
          */
         lock_kernel();
-        ret = ptrace_get_task_struct(request, pid, &child);
-        if (!child)
+        if (request == PTRACE_TRACEME) {
+                ret = ptrace_traceme();
                 goto out;
+        }
+
+        child = ptrace_get_task_struct(pid);
+        if (IS_ERR(child)) {
+                ret = PTR_ERR(child);
+                goto out;
+        }
 
         if (request == PTRACE_ATTACH) {
                 ret = ptrace_attach(child);