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Date: Fri, 4 Jan 2008 15:19:31 +0000
From: Al Viro <viro@...IV.linux.org.uk>
To: Guillaume Chazarain <guichaz@...oo.fr>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] proc: return -EPERM when preventing read of /proc/*/maps
On Fri, Jan 04, 2008 at 03:35:57PM +0100, Guillaume Chazarain wrote:
> Al Viro <viro@...IV.linux.org.uk> wrote:
>
> > vma_stop() doesn't need changes either...
>
> Hmmm, not sure ;-)
Umm... Actually, m_next() and m_stop() both appear to be too convoluted.
* m_next() never gets v == NULL
* the only reason why we do that mmput et.al. both from ->next() and
->stop() is that we try to avoid having priv->mm; why bother?
* why the _hell_ is proc_maps_private defined in include/linux/proc_fs.h,
of all places?
* while we are at it, why is it in any header at all? Having that sucker
in task_mmu.c and task_nommu.c would be more than enough (and we'd avoid
that ifdef in definition, while we are at it).
How about this:
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 7411bfb..3aebc85 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -219,7 +219,7 @@ out:
task_unlock(task);
up_read(&mm->mmap_sem);
mmput(mm);
- return NULL;
+ return ERR_PTR(-EPERM);
}
static int proc_pid_cmdline(struct task_struct *task, char * buffer)
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 8043a3e..75bef20 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -131,12 +131,19 @@ struct pmd_walker {
unsigned long, void *);
};
+struct proc_maps_private {
+ struct pid *pid;
+ struct task_struct *task;
+ struct vm_area_struct *tail_vma;
+ struct mm_struct *mm;
+};
+
static int show_map_internal(struct seq_file *m, void *v, struct mem_size_stats *mss)
{
struct proc_maps_private *priv = m->private;
struct task_struct *task = priv->task;
+ struct mm_struct *mm = priv->mm;
struct vm_area_struct *vma = v;
- struct mm_struct *mm = vma->vm_mm;
struct file *file = vma->vm_file;
int flags = vma->vm_flags;
unsigned long ino = 0;
@@ -381,6 +388,7 @@ static void *m_start(struct seq_file *m, loff_t *pos)
/* Clear the per syscall fields in priv */
priv->task = NULL;
+ priv->mm = NULL;
priv->tail_vma = NULL;
/*
@@ -398,10 +406,11 @@ static void *m_start(struct seq_file *m, loff_t *pos)
return NULL;
mm = mm_for_maps(priv->task);
- if (!mm)
- return NULL;
+ if (!mm || IS_ERR(mm))
+ return ERR_CAST(mm);
priv->tail_vma = tail_vma = get_gate_vma(priv->task);
+ priv->mm = mm;
/* Start with last addr hint */
if (last_addr && (vma = find_vma(mm, last_addr))) {
@@ -430,20 +439,9 @@ out:
/* End of vmas has been reached */
m->version = (tail_vma != NULL)? 0: -1UL;
- up_read(&mm->mmap_sem);
- mmput(mm);
return tail_vma;
}
-static void vma_stop(struct proc_maps_private *priv, struct vm_area_struct *vma)
-{
- if (vma && vma != priv->tail_vma) {
- struct mm_struct *mm = vma->vm_mm;
- up_read(&mm->mmap_sem);
- mmput(mm);
- }
-}
-
static void *m_next(struct seq_file *m, void *v, loff_t *pos)
{
struct proc_maps_private *priv = m->private;
@@ -451,18 +449,22 @@ static void *m_next(struct seq_file *m, void *v, loff_t *pos)
struct vm_area_struct *tail_vma = priv->tail_vma;
(*pos)++;
- if (vma && (vma != tail_vma) && vma->vm_next)
+ if (vma == tail_vma)
+ return NULL;
+ else if (vma->vm_next)
return vma->vm_next;
- vma_stop(priv, vma);
- return (vma != tail_vma)? tail_vma: NULL;
+ else
+ return tail_vma;
}
static void m_stop(struct seq_file *m, void *v)
{
struct proc_maps_private *priv = m->private;
- struct vm_area_struct *vma = v;
- vma_stop(priv, vma);
+ if (priv->mm) {
+ up_read(&priv->mm->mmap_sem);
+ mmput(priv->mm);
+ }
if (priv->task)
put_task_struct(priv->task);
}
diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c
index 1932c2c..a156b62 100644
--- a/fs/proc/task_nommu.c
+++ b/fs/proc/task_nommu.c
@@ -138,6 +138,12 @@ out:
return result;
}
+struct proc_maps_private {
+ struct pid *pid;
+ struct task_struct *task;
+ struct mm_struct *mm;
+};
+
/*
* display mapping lines for a particular process's /proc/pid/maps
*/
@@ -161,16 +167,16 @@ static void *m_start(struct seq_file *m, loff_t *pos)
loff_t n = *pos;
/* pin the task and mm whilst we play with them */
+ priv->mm = NULL;
priv->task = get_pid_task(priv->pid, PIDTYPE_PID);
if (!priv->task)
return NULL;
mm = mm_for_maps(priv->task);
- if (!mm) {
- put_task_struct(priv->task);
- priv->task = NULL;
- return NULL;
- }
+ if (!mm || IS_ERR(mm))
+ return ERR_CAST(mm);
+
+ priv->mm = mm;
/* start from the Nth VMA */
for (vml = mm->context.vmlist; vml; vml = vml->next)
@@ -183,12 +189,12 @@ static void m_stop(struct seq_file *m, void *_vml)
{
struct proc_maps_private *priv = m->private;
- if (priv->task) {
- struct mm_struct *mm = priv->task->mm;
- up_read(&mm->mmap_sem);
- mmput(mm);
- put_task_struct(priv->task);
+ if (priv->mm) {
+ up_read(&priv->mm->mmap_sem);
+ mmput(priv->mm);
}
+ if (priv->task)
+ put_task_struct(priv->task);
}
static void *m_next(struct seq_file *m, void *_vml, loff_t *pos)
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index a531682..192a5c4 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -286,12 +286,4 @@ static inline struct net *PDE_NET(struct proc_dir_entry *pde)
struct net *get_proc_net(const struct inode *inode);
-struct proc_maps_private {
- struct pid *pid;
- struct task_struct *task;
-#ifdef CONFIG_MMU
- struct vm_area_struct *tail_vma;
-#endif
-};
-
#endif /* _LINUX_PROC_FS_H */
--
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