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authorChristopher Yeoh <cyeoh@au1.ibm.com>2012-02-02 11:34:09 +1030
committerLinus Torvalds <torvalds@linux-foundation.org>2012-02-02 12:55:17 -0800
commit8cdb878dcb359fd1137e9abdee9322f5e9bcfdf8 (patch)
tree146afc01f3c1d7cbc944328484d077032bc53bfd /kernel/fork.c
parent24b36da33c64368775f4ef9386d44dce1d2bc8cf (diff)
Fix race in process_vm_rw_core
This fixes the race in process_vm_core found by Oleg (see http://article.gmane.org/gmane.linux.kernel/1235667/ for details). This has been updated since I last sent it as the creation of the new mm_access() function did almost exactly the same thing as parts of the previous version of this patch did. In order to use mm_access() even when /proc isn't enabled, we move it to kernel/fork.c where other related process mm access functions already are. Signed-off-by: Chris Yeoh <yeohc@au1.ibm.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/fork.c')
-rw-r--r--kernel/fork.c20
1 files changed, 20 insertions, 0 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index 051f090d40c1..1b2ef3c23ae4 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -647,6 +647,26 @@ struct mm_struct *get_task_mm(struct task_struct *task)
}
EXPORT_SYMBOL_GPL(get_task_mm);
+struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
+{
+ struct mm_struct *mm;
+ int err;
+
+ err = mutex_lock_killable(&task->signal->cred_guard_mutex);
+ if (err)
+ return ERR_PTR(err);
+
+ mm = get_task_mm(task);
+ if (mm && mm != current->mm &&
+ !ptrace_may_access(task, mode)) {
+ mmput(mm);
+ mm = ERR_PTR(-EACCES);
+ }
+ mutex_unlock(&task->signal->cred_guard_mutex);
+
+ return mm;
+}
+
/* Please note the differences between mmput and mm_release.
* mmput is called whenever we stop holding onto a mm_struct,
* error success whatever.