From: WANG Cong <xiyou.wangcong@xxxxxxxxx>
V2: move the check into m_stop() as suggested by Linus,
also, most ->show() implementations assume the second parameter 'v'
is not NULL, this fixes them too.
Anca reported a bug:
[15117.080119] BUG: unable to handle kernel paging request at fffffffffffffff3
[15117.080152] IP: [<ffffffff811b4989>] vma_stop+0x19/0x40
Linus did the initial analysis, and found this was caused
by commit ec6fd8a4355c ("report errors in /proc/*/*map*
sanely"), which replaces NULL with various ERR_PTR() cases.
This is true, that commit changed the return value of m_start(),
which will return an error pointer on failure, but Al forgot
to check the error pointer in m_stop() which will be called
when m_start() fails. This patches fixes it.
Reported-by: Anca Emanuel <anca.emanuel@xxxxxxxxx>
Tested-by: Anca Emanuel <anca.emanuel@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: WANG Cong <amwang@xxxxxxxxxx>
Signed-off-by: WANG Cong <xiyou.wangcong@xxxxxxxxx>
---
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 7c708a4..8e59169 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -124,8 +124,10 @@ static void *m_start(struct seq_file *m, loff_t *pos)
return ERR_PTR(-ESRCH);
mm = mm_for_maps(priv->task);
- if (!mm || IS_ERR(mm))
+ if (IS_ERR_OR_NULL(mm)) {
+ put_task_struct(priv->task);
return mm;
+ }
down_read(&mm->mmap_sem);
tail_vma = get_gate_vma(priv->task->mm);
@@ -182,6 +184,8 @@ static void m_stop(struct seq_file *m, void *v)
struct proc_maps_private *priv = m->private;
struct vm_area_struct *vma = v;
+ if (IS_ERR_OR_NULL(v))
+ return;
vma_stop(priv, vma);
if (priv->task)
put_task_struct(priv->task);
diff --git a/fs/seq_file.c b/fs/seq_file.c
index 05d6b0e..e17d5e6 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -83,7 +83,7 @@ static int traverse(struct seq_file *m, loff_t offset)
p = m->op->start(m, &index);
while (p) {
error = PTR_ERR(p);
- if (IS_ERR(p))
+ if (IS_ERR_OR_NULL(p))
break;
error = m->op->show(m, p);
if (error < 0)
--
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