uprobe_copy_process() assumes that the new child doesn't need ->utask, it should be allocated by demand.
But this is not true if the forking task has the pending ret- probes, the child should report them as well and thus it needs the copy of parent's ->return_instances chain. Otherwise the child crashes when it returns from the probed function. Note: this change alone doesn't fix the problem, see the next change. Cc: [email protected] # 3.9+ Reported-by: Martin Cermak <[email protected]> Reported-by: David Smith <[email protected]> Signed-off-by: Oleg Nesterov <[email protected]> --- kernel/events/uprobes.c | 43 +++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 43 insertions(+), 0 deletions(-) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index c836135..67b65c8 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -1366,12 +1366,55 @@ static struct uprobe_task *get_utask(void) return current->utask; } +static int dup_utask(struct task_struct *t, struct uprobe_task *o_utask) +{ + struct uprobe_task *n_utask; + struct return_instance **p, *o, *n; + + n_utask = kzalloc(sizeof(struct uprobe_task), GFP_KERNEL); + if (!n_utask) + return -ENOMEM; + t->utask = n_utask; + + p = &n_utask->return_instances; + for (o = o_utask->return_instances; o; o = o->next) { + n = kmalloc(sizeof(struct return_instance), GFP_KERNEL); + if (!n) + return -ENOMEM; + + *n = *o; + atomic_inc(&n->uprobe->ref); + n->next = NULL; + + *p = n; + p = &n->next; + n_utask->depth++; + } + + return 0; +} + +static void uprobe_warn(struct task_struct *t, const char *msg) +{ + pr_warn("uprobe: %s:%d failed to %s\n", + current->comm, current->pid, msg); +} + /* * Called in context of a new clone/fork from copy_process. */ void uprobe_copy_process(struct task_struct *t) { + struct uprobe_task *utask = current->utask; + struct mm_struct *mm = current->mm; + t->utask = NULL; + + if (mm == t->mm || !utask || !utask->return_instances) + return; + + if (dup_utask(t, utask)) + return uprobe_warn(t, "dup ret instances"); } /* -- 1.5.5.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
