Messages in this thread | | | Date | Sat, 5 Oct 2013 07:34:32 +0100 | From | Al Viro <> | Subject | Re: [PATCH] kernel/exit.c: call read_unlock() when failure occurs after already called read_lock() in do_wait(). |
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On Sat, Oct 05, 2013 at 01:53:26PM +0800, Chen Gang wrote: > If failure occurs after called read_lock(), need call read_unlock() too. > > It can fail in multiple position, so add new tag 'fail_lock' for it > (also can let 'if' only content one jump statement).
You know, this is getting too frequent... You really need to do something about it. OK, you've formed a hypothesis (in this case, that ptrace_do_wait() returns non-zero with tasklist_lock still held). If that hypothesis was correct, you would've found a bug and yes, this patch would probably be more or less a fix for that bug.
Do you see what's missing? That's right, verifying that hypothesis. Which isn't hard to do, either by slapping a printk into these exits, or by trying to build a proof. As it is, hypothesis is incorrect and your patch introduces breakage. The same would have happened if _some_ exits from that function returned non-zero values with tasklist_lock held and some returned non-zero values with tasklist_lock released.
You really need to realize that pattern-matching is not enough - you need to prove that your fix is correct and that requires an analysis of what's there.
"I see something odd" is a good reason to ask or to try and figure out what's going on. It's not a good reason for blindly making changes like that - not until you've done the analysis and can at least show that it won't _break_ things.
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