Messages in this thread | | | Date | Fri, 22 Apr 2011 15:04:30 +0200 | From | Chris Metcalf <> | Subject | Re: arch/tile/kernel/hardwall.c:do_hardwall_trap unsafe/wrong usage of ->sighand |
| |
On 4/21/2011 9:03 PM, Oleg Nesterov wrote: > On 04/18, Oleg Nesterov wrote: >> On 04/16, Matt Fleming wrote: >>> 3. I suspect most people find the rules of ->sighand pretty >>> confusing. Just look at >>> >>> arch/tile/kernel/hardwall.c:do_hardwall_trap() >>> >>> the use of siglock there looks buggy to me. >> Indeed, I agree. It shouldn't use __group_send_sig_info() at all. >> I'll send the patch. Nobody outside of signal code should play with >> ->sighand, this is almost always wrong. > Hmm. It turns out, I can't make the patch because I do not understand > what this code tries to do. > > hardwall_activate() adds the thread to hardwall_list, but do_hardwall_trap() > sends the signal to the whole process. I know nothing about arch/tile and > probably this is correct, but could you confirm this?
Yes, the intended behavior is to send the signal to the process, as a way of indicating the OS's displeasure with sending a malformed packet on the user network. But I think sending it to the specific thread is reasonable too; I don't have a strong preference in this design.
> Note that SIGILL can be delivered to another thread in the thread-group, is > it correct? > > Also. Is it supposed that SIGILL can have a hanlder or can be blocked, or > it should always kill the whole thread group?
A handler would be reasonable for the process.
> I think we need the patch below, assuming that SIGILL should be sent to > the single thread and it is fine to have a handler for SIGILL.
Thanks; I appreciate the additional code review in any case. I'll look at the ramifications of the change in more detail when I return from vacation late next week.
> Oleg. > > --- sigprocmask/arch/tile/kernel/hardwall.c~1_sighand 2011-04-06 21:33:42.000000000 +0200 > +++ sigprocmask/arch/tile/kernel/hardwall.c 2011-04-21 20:56:36.000000000 +0200 > @@ -268,12 +268,10 @@ void __kprobes do_hardwall_trap(struct p > found_processes = 0; > list_for_each_entry(p, &rect->task_head, thread.hardwall_list) { > BUG_ON(p->thread.hardwall != rect); > - if (p->sighand) { > + if (!(p->flags & PF_EXITING)) { > found_processes = 1; > pr_notice("hardwall: killing %d\n", p->pid); > - spin_lock(&p->sighand->siglock); > - __group_send_sig_info(info.si_signo, &info, p); > - spin_unlock(&p->sighand->siglock); > + do_send_sig_info(info.si_signo, &info, p, false); > } > } > if (!found_processes) >
-- Chris Metcalf, Tilera Corp. http://www.tilera.com
| |