aboutsummaryrefslogtreecommitdiffstats
path: root/fs
diff options
context:
space:
mode:
authorOleg Nesterov <oleg@redhat.com>2009-07-09 21:27:40 -0400
committerJames Morris <jmorris@namei.org>2009-08-10 06:49:26 -0400
commit704b836cbf19e885f8366bccb2e4b0474346c02d (patch)
treed0513d3ef70e1b875cd7786f94150ba2428b6a88 /fs
parent00f89d218523b9bf6b522349c039d5ac80aa536d (diff)
mm_for_maps: take ->cred_guard_mutex to fix the race with exec
The problem is minor, but without ->cred_guard_mutex held we can race with exec() and get the new ->mm but check old creds. Now we do not need to re-check task->mm after ptrace_may_access(), it can't be changed to the new mm under us. Strictly speaking, this also fixes another very minor problem. Unless security check fails or the task exits mm_for_maps() should never return NULL, the caller should get either old or new ->mm. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Serge Hallyn <serue@us.ibm.com> Signed-off-by: James Morris <jmorris@namei.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/proc/base.c22
1 files changed, 11 insertions, 11 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c
index f3c2e4085fed..175db258942f 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -234,19 +234,19 @@ static int check_mem_permission(struct task_struct *task)
234 234
235struct mm_struct *mm_for_maps(struct task_struct *task) 235struct mm_struct *mm_for_maps(struct task_struct *task)
236{ 236{
237 struct mm_struct *mm = get_task_mm(task); 237 struct mm_struct *mm;
238 238
239 if (mm && mm != current->mm) { 239 if (mutex_lock_killable(&task->cred_guard_mutex))
240 /* 240 return NULL;
241 * task->mm can be changed before security check, 241
242 * in that case we must notice the change after. 242 mm = get_task_mm(task);
243 */ 243 if (mm && mm != current->mm &&
244 if (!ptrace_may_access(task, PTRACE_MODE_READ) || 244 !ptrace_may_access(task, PTRACE_MODE_READ)) {
245 mm != task->mm) { 245 mmput(mm);
246 mmput(mm); 246 mm = NULL;
247 mm = NULL;
248 }
249 } 247 }
248 mutex_unlock(&task->cred_guard_mutex);
249
250 return mm; 250 return mm;
251} 251}
252 252