Messages in this thread Patch in this message | | | From | David Howells <> | Subject | [PATCH 2/2] CRED: Guard the setprocattr security hook against ptrace | Date | Fri, 08 May 2009 13:55:27 +0100 |
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Guard the setprocattr security hook against ptrace by taking the target task's cred_guard_mutex around it. The problem is that setprocattr() may otherwise note the lack of a debugger, and then perform an action on that basis whilst letting a debugger attach between the two points. Holding cred_guard_mutex across the test and the action prevents ptrace_attach() from doing that.
Signed-off-by: David Howells <dhowells@redhat.com> ---
fs/proc/base.c | 6 ++++++ 1 files changed, 6 insertions(+), 0 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c index fb45615..23342e1 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -2128,9 +2128,15 @@ static ssize_t proc_pid_attr_write(struct file * file, const char __user * buf, if (copy_from_user(page, buf, count)) goto out_free; + /* Guard against adverse ptrace interaction */ + length = mutex_lock_interruptible(&task->cred_guard_mutex); + if (length < 0) + goto out_free; + length = security_setprocattr(task, (char*)file->f_path.dentry->d_name.name, (void*)page, count); + mutex_unlock(&task->cred_guard_mutex); out_free: free_page((unsigned long) page); out:
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