From 831830b5a2b5d413407adf380ef62fe17d6fcbf2 Mon Sep 17 00:00:00 2001
From: Al Viro <viro@ZenIV.linux.org.uk>
Date: Wed, 2 Jan 2008 14:09:57 +0000
Subject: [PATCH] restrict reading from /proc/<pid>/maps to those who share
->mm or can ptrace pid
Contents of /proc/*/maps is sensitive and may become sensitive after
open() (e.g. if target originally shares our ->mm and later does exec
on suid-root binary).
Check at read() (actually, ->start() of iterator) time that mm_struct
we'd grabbed and locked is
- still the ->mm of target
- equal to reader's ->mm or the target is ptracable by reader.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
fs/proc/base.c | 20 ++++++++++++++++++++
fs/proc/internal.h | 2 ++
fs/proc/task_mmu.c | 3 +--
fs/proc/task_nommu.c | 4 +---
include/linux/ptrace.h | 1 +
kernel/ptrace.c | 4 ++--
6 files changed, 27 insertions(+), 7 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 02a63ac04178e..7411bfb0b7cce 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -202,6 +202,26 @@ 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))
+struct mm_struct *mm_for_maps(struct task_struct *task)
+{
+ struct mm_struct *mm = get_task_mm(task);
+ if (!mm)
+ return NULL;
+ down_read(&mm->mmap_sem);
+ task_lock(task);
+ if (task->mm != mm)
+ goto out;
+ if (task->mm != current->mm && __ptrace_may_attach(task) < 0)
+ goto out;
+ task_unlock(task);
+ return mm;
+out:
+ task_unlock(task);
+ up_read(&mm->mmap_sem);
+ mmput(mm);
+ return NULL;
+}
+
static int proc_pid_cmdline(struct task_struct *task, char * buffer)
{
int res = 0;
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index 1820eb2ef7623..05b3e9006262c 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -27,6 +27,8 @@ struct vmalloc_info {
unsigned long largest_chunk;
};
+extern struct mm_struct *mm_for_maps(struct task_struct *);
+
#ifdef CONFIG_MMU
#define VMALLOC_TOTAL (VMALLOC_END - VMALLOC_START)
extern void get_vmalloc_info(struct vmalloc_info *vmi);
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index c24d81a5a040e..8043a3eab52ce 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -397,12 +397,11 @@ static void *m_start(struct seq_file *m, loff_t *pos)
if (!priv->task)
return NULL;
- mm = get_task_mm(priv->task);
+ mm = mm_for_maps(priv->task);
if (!mm)
return NULL;
priv->tail_vma = tail_vma = get_gate_vma(priv->task);
- down_read(&mm->mmap_sem);
/* Start with last addr hint */
if (last_addr && (vma = find_vma(mm, last_addr))) {
diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c
index d8b8c7183c243..1932c2ca34572 100644
--- a/fs/proc/task_nommu.c
+++ b/fs/proc/task_nommu.c
@@ -165,15 +165,13 @@ static void *m_start(struct seq_file *m, loff_t *pos)
if (!priv->task)
return NULL;
- mm = get_task_mm(priv->task);
+ mm = mm_for_maps(priv->task);
if (!mm) {
put_task_struct(priv->task);
priv->task = NULL;
return NULL;
}
- down_read(&mm->mmap_sem);
-
/* start from the Nth VMA */
for (vml = mm->context.vmlist; vml; vml = vml->next)
if (n-- == 0)
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index ae8146abd7463..3ea5750a0f7e2 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -97,6 +97,7 @@ extern void __ptrace_link(struct task_struct *child,
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);
+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 7c76f2ffaeaad..0c65d306f4120 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -120,7 +120,7 @@ int ptrace_check_attach(struct task_struct *child, int kill)
return ret;
}
-static int may_attach(struct task_struct *task)
+int __ptrace_may_attach(struct task_struct *task)
{
/* May we inspect the given task?
* This check is used both for attaching with ptrace
@@ -154,7 +154,7 @@ int ptrace_may_attach(struct task_struct *task)
{
int err;
task_lock(task);
- err = may_attach(task);
+ err = __ptrace_may_attach(task);
task_unlock(task);
return !err;
}
--
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