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uprobes/tracing: Fully initialize uprobe_trace_consumer before uprobe_register()

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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 <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
This commit is contained in:
Oleg Nesterov 2013-01-27 18:36:24 +01:00
parent 84d7ed799f
commit 4161824f18
1 changed files with 9 additions and 8 deletions
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17
kernel/trace/trace_uprobe.c
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@ -552,17 +552,18 @@ static int probe_event_enable(struct trace_uprobe *tu, int flag)
return -EINTR;
utc->cons.handler = uprobe_dispatcher;
ret = uprobe_register(tu->inode, tu->offset, &utc->cons);
if (ret) {
kfree(utc);
return ret;
}
tu->flags |= flag;
utc->tu = tu;
tu->consumer = utc;
tu->flags |= flag;
return 0;
ret = uprobe_register(tu->inode, tu->offset, &utc->cons);
if (ret) {
tu->consumer = NULL;
tu->flags &= ~flag;
kfree(utc);
}
return ret;
}
static void probe_event_disable(struct trace_uprobe *tu, int flag)