[PATCH] remove duplicated code from proc and ptrace

Extract common code used by ptrace_attach() and may_ptrace_attach()
into a separate function.

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Cc: <viro@parcelfarce.linux.theplanet.co.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 33 insertions, 44 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 24eed139e54e..84751f3f52d5 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -346,33 +346,6 @@ static int proc_root_link(struct inode *inode, struct dentry **dentry, struct vf
          (task->state == TASK_STOPPED || task->state == TASK_TRACED) && \
          security_ptrace(current,task) == 0))
 
-static int may_ptrace_attach(struct task_struct *task)
-{
-        int retval = 0;
-
-        task_lock(task);
-
-        if (!task->mm)
-                goto out;
-        if (((current->uid != task->euid) ||
-             (current->uid != task->suid) ||
-             (current->uid != task->uid) ||
-             (current->gid != task->egid) ||
-             (current->gid != task->sgid) ||
-             (current->gid != task->gid)) && !capable(CAP_SYS_PTRACE))
-                goto out;
-        rmb();
-        if (task->mm->dumpable != 1 && !capable(CAP_SYS_PTRACE))
-                goto out;
-        if (security_ptrace(current, task))
-                goto out;
-
-        retval = 1;
-out:
-        task_unlock(task);
-        return retval;
-}
-
 static int proc_pid_environ(struct task_struct *task, char * buffer)
 {
         int res = 0;
@@ -382,7 +355,7 @@ static int proc_pid_environ(struct task_struct *task, char * buffer)
                 if (len > PAGE_SIZE)
                         len = PAGE_SIZE;
                 res = access_process_vm(task, mm->env_start, buffer, len, 0);
-                if (!may_ptrace_attach(task))
+                if (!ptrace_may_attach(task))
                         res = -ESRCH;
                 mmput(mm);
         }
@@ -685,7 +658,7 @@ static ssize_t mem_read(struct file * file, char __user * buf,
         int ret = -ESRCH;
         struct mm_struct *mm;
 
-        if (!MAY_PTRACE(task) || !may_ptrace_attach(task))
+        if (!MAY_PTRACE(task) || !ptrace_may_attach(task))
                 goto out;
 
         ret = -ENOMEM;
@@ -711,7 +684,7 @@ static ssize_t mem_read(struct file * file, char __user * buf,
 
                 this_len = (count > PAGE_SIZE) ? PAGE_SIZE : count;
                 retval = access_process_vm(task, src, page, this_len, 0);
-                if (!retval || !MAY_PTRACE(task) || !may_ptrace_attach(task)) {
+                if (!retval || !MAY_PTRACE(task) || !ptrace_may_attach(task)) {
                         if (!ret)
                                 ret = -EIO;
                         break;
@@ -749,7 +722,7 @@ static ssize_t mem_write(struct file * file, const char * buf,
         struct task_struct *task = proc_task(file->f_dentry->d_inode);
         unsigned long dst = *ppos;
 
-        if (!MAY_PTRACE(task) || !may_ptrace_attach(task))
+        if (!MAY_PTRACE(task) || !ptrace_may_attach(task))
                 return -ESRCH;
 
         page = (char *)__get_free_page(GFP_USER);
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index 2afdafb62123..dc6f3647bfbc 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -90,6 +90,7 @@ extern void __ptrace_link(struct task_struct *child,
                           struct task_struct *new_parent);
 extern void __ptrace_unlink(struct task_struct *child);
 extern void ptrace_untrace(struct task_struct *child);
+extern int ptrace_may_attach(struct task_struct *task);
 
 static inline void ptrace_link(struct task_struct *child,
                                struct task_struct *new_parent)
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 8dcb8f6288bc..019e04ec065a 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -118,6 +118,33 @@ int ptrace_check_attach(struct task_struct *child, int kill)
         return ret;
 }
 
+static int may_attach(struct task_struct *task)
+{
+        if (!task->mm)
+                return -EPERM;
+        if (((current->uid != task->euid) ||
+             (current->uid != task->suid) ||
+             (current->uid != task->uid) ||
+             (current->gid != task->egid) ||
+             (current->gid != task->sgid) ||
+             (current->gid != task->gid)) && !capable(CAP_SYS_PTRACE))
+                return -EPERM;
+        smp_rmb();
+        if (!task->mm->dumpable && !capable(CAP_SYS_PTRACE))
+                return -EPERM;
+
+        return security_ptrace(current, task);
+}
+
+int ptrace_may_attach(struct task_struct *task)
+{
+        int err;
+        task_lock(task);
+        err = may_attach(task);
+        task_unlock(task);
+        return !err;
+}
+
 int ptrace_attach(struct task_struct *task)
 {
         int retval;
@@ -127,22 +154,10 @@ int ptrace_attach(struct task_struct *task)
                 goto bad;
         if (task == current)
                 goto bad;
-        if (!task->mm)
-                goto bad;
-        if(((current->uid != task->euid) ||
-            (current->uid != task->suid) ||
-            (current->uid != task->uid) ||
-            (current->gid != task->egid) ||
-            (current->gid != task->sgid) ||
-            (current->gid != task->gid)) && !capable(CAP_SYS_PTRACE))
-                goto bad;
-        smp_rmb();
-        if (!task->mm->dumpable && !capable(CAP_SYS_PTRACE))
-                goto bad;
         /* the same process cannot be attached many times */
         if (task->ptrace & PT_PTRACED)
                 goto bad;
-        retval = security_ptrace(current, task);
+        retval = may_attach(task);
         if (retval)
                 goto bad;