report errors in /proc/*/*map* sanely

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

3 files changed, 13 insertions, 11 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index df73573e12c9..c28281102082 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -225,15 +225,17 @@ static int check_mem_permission(struct task_struct *task)
 struct mm_struct *mm_for_maps(struct task_struct *task)
 {
         struct mm_struct *mm;
+        int err;
 
-        if (mutex_lock_killable(&task->signal->cred_guard_mutex))
-                return NULL;
+        err =  mutex_lock_killable(&task->signal->cred_guard_mutex);
+        if (err)
+                return ERR_PTR(err);
 
         mm = get_task_mm(task);
         if (mm && mm != current->mm &&
                         !ptrace_may_access(task, PTRACE_MODE_READ)) {
                 mmput(mm);
-                mm = NULL;
+                mm = ERR_PTR(-EACCES);
         }
         mutex_unlock(&task->signal->cred_guard_mutex);
 
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index c966413c139b..8fed0f88fbf7 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -119,11 +119,11 @@ static void *m_start(struct seq_file *m, loff_t *pos)
 
         priv->task = get_pid_task(priv->pid, PIDTYPE_PID);
         if (!priv->task)
-                return NULL;
+                return ERR_PTR(-ESRCH);
 
         mm = mm_for_maps(priv->task);
-        if (!mm)
-                return NULL;
+        if (!mm || IS_ERR(mm))
+                return mm;
         down_read(&mm->mmap_sem);
 
         tail_vma = get_gate_vma(priv->task);
@@ -728,9 +728,9 @@ static ssize_t pagemap_read(struct file *file, char __user *buf,
         if (!task)
                 goto out;
 
-        ret = -EACCES;
         mm = mm_for_maps(task);
-        if (!mm)
+        ret = PTR_ERR(mm);
+        if (!mm || IS_ERR(mm))
                 goto out_task;
 
         ret = -EINVAL;
diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c
index b535d3e5d5f1..980de547c070 100644
--- a/fs/proc/task_nommu.c
+++ b/fs/proc/task_nommu.c
@@ -199,13 +199,13 @@ static void *m_start(struct seq_file *m, loff_t *pos)
         /* pin the task and mm whilst we play with them */
         priv->task = get_pid_task(priv->pid, PIDTYPE_PID);
         if (!priv->task)
-                return NULL;
+                return ERR_PTR(-ESRCH);
 
         mm = mm_for_maps(priv->task);
-        if (!mm) {
+        if (!mm || IS_ERR(mm)) {
                 put_task_struct(priv->task);
                 priv->task = NULL;
-                return NULL;
+                return mm;
         }
         down_read(&mm->mmap_sem);