From: Oleg Nesterov Date: Sun, 27 Jan 2013 17:36:24 +0000 (+0100) Subject: uprobes/tracing: Fully initialize uprobe_trace_consumer before uprobe_register() X-Git-Tag: firefly_0821_release~3680^2~1126^2~2^2~10 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=4161824f18ff4f56f46595a4016c7315dd0d24f1;p=firefly-linux-kernel-4.4.55.git uprobes/tracing: Fully initialize uprobe_trace_consumer before uprobe_register() probe_event_enable() does uprobe_register() and only after that sets utc->tu and tu->consumer/flags. This can race with uprobe_dispatcher() which can miss these assignments or see them out of order. Nothing really bad can happen, but this doesn't look clean/safe. And this does not allow to use uprobe_consumer->filter() we are going to add, it is called by uprobe_register() and it needs utc->tu. Change this code to initialize everything before uprobe_register(), and reset tu->consumer/flags if it fails. We can't race with event_disable(), the caller holds event_mutex, and if we could the code would be wrong anyway. In fact I think uprobe_trace_consumer should die, it buys nothing but complicates the code. We can simply add uprobe_consumer into trace_uprobe. Signed-off-by: Oleg Nesterov Acked-by: Srikar Dronamraju --- diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c index 06c22bad776a..15b8eceeddc5 100644 --- a/kernel/trace/trace_uprobe.c +++ b/kernel/trace/trace_uprobe.c @@ -552,17 +552,18 @@ static int probe_event_enable(struct trace_uprobe *tu, int flag) return -EINTR; utc->cons.handler = uprobe_dispatcher; + utc->tu = tu; + tu->consumer = utc; + tu->flags |= flag; + ret = uprobe_register(tu->inode, tu->offset, &utc->cons); if (ret) { + tu->consumer = NULL; + tu->flags &= ~flag; kfree(utc); - return ret; } - tu->flags |= flag; - utc->tu = tu; - tu->consumer = utc; - - return 0; + return ret; } static void probe_event_disable(struct trace_uprobe *tu, int flag)