Re: [2.6.31 and later] "struct pid" leak.

[Oleg Nesterov <oleg@redhat.com>]

On 03/31, Andrew Morton wrote:
>
> On Tue, 30 Mar 2010 16:31:13 +0100
> Catalin Marinas <catalin.marinas@arm.com> wrote:
>
> > Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> wrote:
> > > I got below report with 2.6.33.1 .
> > >
> > > unreferenced object 0xde144600 (size 64):
> > >   comm "init", pid 1, jiffies 4294678101 (age 291.508s)
> > >   hex dump (first 32 bytes):
> > >     02 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> > >     00 00 00 00 04 76 ae de d1 76 43 c0 d6 08 00 00  .....v...vC.....
> > >   backtrace:
> > >     [<c0481704>] create_object+0x121/0x1ef
> > >     [<c05f546b>] kmemleak_alloc+0x25/0x42
> > >     [<c047e326>] kmemleak_alloc_recursive+0x1c/0x22
> > >     [<c047e36e>] kmem_cache_alloc+0x42/0x68
> > >     [<c0437701>] alloc_pid+0x19/0x288
> > >     [<c0428acc>] copy_process+0x95a/0xdac
> > >     [<c04290d8>] do_fork+0x129/0x261
> > >     [<c0407de5>] sys_clone+0x1f/0x24
> > >     [<c040292d>] ptregs_clone+0x15/0x28
> > >     [<ffffffff>] 0xffffffff
> > > unreferenced object 0xdfa96a40 (size 64):
> > >   comm "login", pid 2259, jiffies 4294719437 (age 250.179s)
> > >   hex dump (first 32 bytes):
> > >     02 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> > >     00 00 00 00 60 39 ae de d1 76 43 c0 bb 09 00 00  ....`9...vC.....
> > >   backtrace:
> > >     [<c0481704>] create_object+0x121/0x1ef
> > >     [<c05f546b>] kmemleak_alloc+0x25/0x42
> > >     [<c047e326>] kmemleak_alloc_recursive+0x1c/0x22
> > >     [<c047e36e>] kmem_cache_alloc+0x42/0x68
> > >     [<c0437701>] alloc_pid+0x19/0x288
> > >     [<c0428acc>] copy_process+0x95a/0xdac
> > >     [<c04290d8>] do_fork+0x129/0x261
> > >     [<c0407de5>] sys_clone+0x1f/0x24
> > >     [<c040292d>] ptregs_clone+0x15/0x28
> > >     [<ffffffff>] 0xffffffff
> >
> > I reported similar leaks last year -
> > http://lkml.org/lkml/2009/7/8/422. There is some analysis in the thread
> > above of the reference counting but I couldn't figure out where it goes
> > wrong. It looks to me like there isn't any reference to a struct pid
> > block but its reference count is 2.
> >
> > There is a bugzilla entry as well -
> > https://bugzilla.kernel.org/show_bug.cgi?id=13868
> >
>
> Let's bug some people by cc'ing them ;)

Oh. It is hardly possibly to find the unbalanced get_pid() via grep.

IIRC, I sent the debugging patch which tracks get/put pid, but I can't
recall if anybody tried this patch. Hmm, and I can't find that patch
or the previous discussion in my maildir...

Catalin, Tetsuo, any chance you can remind me if this patch was used?

Oleg.