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authorLinus Torvalds <torvalds@linux-foundation.org>2017-05-27 08:52:27 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-05-27 08:52:27 -0700
commitd024baa58a4a7e5eb6058017771d15b9e47b56db (patch)
tree03e0a3338ecc033942c48acf51bac9138ef0dfd6
parent77d64656950b299f5e7c70f1e3a0bdc991b51497 (diff)
parent4d6501dce079c1eb6bf0b1d8f528a5e81770109e (diff)
Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull kthread fix from Thomas Gleixner: "A single fix which prevents a use after free when kthread fork fails" * 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: kthread: Fix use-after-free if kthread fork fails
-rw-r--r--kernel/fork.c17
1 files changed, 12 insertions, 5 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index aa1076c5e4a9..e53770d2bf95 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1577,6 +1577,18 @@ static __latent_entropy struct task_struct *copy_process(
if (!p)
goto fork_out;
+ /*
+ * This _must_ happen before we call free_task(), i.e. before we jump
+ * to any of the bad_fork_* labels. This is to avoid freeing
+ * p->set_child_tid which is (ab)used as a kthread's data pointer for
+ * kernel threads (PF_KTHREAD).
+ */
+ p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
+ /*
+ * Clear TID on mm_release()?
+ */
+ p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
+
ftrace_graph_init_task(p);
rt_mutex_init_task(p);
@@ -1743,11 +1755,6 @@ static __latent_entropy struct task_struct *copy_process(
}
}
- p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
- /*
- * Clear TID on mm_release()?
- */
- p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr : NULL;
#ifdef CONFIG_BLOCK
p->plug = NULL;
#endif