From: Christoph Hellwig <hch@lst.de>
To: viro@zeniv.linux.org.uk, Chunyu Hu <chuhu@redhat.com>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] proc: add proc_seq_release
Date: Wed, 27 Jun 2018 09:09:40 +0200 [thread overview]
Message-ID: <20180627070940.GA9790@lst.de> (raw)
In-Reply-To: <1113263100.13594710.1530015652549.JavaMail.zimbra@redhat.com>
Al, can you pick up this fix from Chunyu?
On Tue, Jun 26, 2018 at 08:20:52AM -0400, Chunyu Hu wrote:
>
>
> ----- Original Message -----
> > From: "Christoph Hellwig" <hch@lst.de>
> > To: "Chunyu Hu" <chuhu@redhat.com>
> > Cc: viro@zeniv.linux.org.uk, hch@lst.de, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
> > Sent: Monday, June 11, 2018 2:23:54 PM
> > Subject: Re: [PATCH] proc: add proc_seq_release
> >
> > On Sun, Jun 10, 2018 at 03:51:24AM +0800, Chunyu Hu wrote:
> > > kmemleak reported some memory leak on reading proc files. After adding
> > > some debug lines, find that proc_seq_fops is using seq_release as
> > > release handler, which won't handle the free of 'private' field of
> > > seq_file, while in fact the open handler proc_seq_open could create
> > > the private data with __seq_open_private when state_size is greater
> > > than zero. So after reading files created with proc_create_seq_private,
> > > such as /proc/timer_list and /proc/vmallocinfo, the private mem of a
> > > seq_file is not freed. Fix it by adding the paired proc_seq_release
> > > as the default release handler of proc_seq_ops instead of seq_release.
> >
> > Indeed, thanks for the patch.
> >
> > Reviewed-by: Christoph Hellwig <hch@lst.de>
> >
>
> What's our plan for this issue? We can still see the leaking in 4.18-RC2.
>
> 1) Run 'cat /proc/timer_list' then
> 2) echo scan > /sys/kernel/debug/kmemleak
> 3) cat /sys/kernel/debug/kmemleak
>
> each time, it leaks 16 bytes.
>
> unreferenced object 0xffff880017525120 (size 16):
> comm "cat", pid 4682, jiffies 4294964743 (age 46.880s)
> hex dump (first 16 bytes):
> 04 00 00 00 01 00 00 00 42 00 96 e7 3f 00 00 00 ........B...?...
> backtrace:
> [<000000006f6b5d90>] seq_open_private+0x25/0x40
> [<00000000d94d91aa>] proc_seq_open+0xca/0x120
> [<00000000d5609077>] proc_reg_open+0x1d4/0x5b0
> [<0000000036a3d49c>] do_dentry_open+0x7d6/0x1010
> [<00000000d4fb0a82>] vfs_open+0x170/0x2b0
> [<00000000f3bf21b4>] path_openat+0x760/0x3750
> [<00000000b0d4e66c>] do_filp_open+0x1bb/0x2c0
> [<0000000063b53236>] do_sys_open+0x2b2/0x490
> [<00000000a5249c62>] do_syscall_64+0xd3/0x6e0
> [<000000006f9f8436>] entry_SYSCALL_64_after_hwframe+0x49/0xbe
> [<000000001d702cb2>] 0xffffffffffffffff
>
>
> --
> Regards,
> Chunyu Hu
---end quoted text---
next prev parent reply other threads:[~2018-06-27 6:59 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-09 19:51 [PATCH] proc: add proc_seq_release Chunyu Hu
2018-06-11 6:23 ` Christoph Hellwig
2018-06-26 12:20 ` Chunyu Hu
2018-06-27 7:09 ` Christoph Hellwig [this message]
2018-06-28 0:43 ` Al Viro
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