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Date: Fri, 19 Jul 2013 12:31:06 -0700
From: "Darrick J. Wong" <darrick.wong@...cle.com>
To: Dave Jones <davej@...hat.com>,
Linux Kernel <linux-kernel@...r.kernel.org>,
linux-ext4@...r.kernel.org, "Theodore Ts'o" <tytso@....edu>,
Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH] ext4: fix a bug when we try to open a file with
O_TMPFILE flag
On Fri, Jul 19, 2013 at 08:14:05PM +0800, Zheng Liu wrote:
> Hi Dave,
>
> After applied this patch, the problem has been fixed in my own sand box.
> But that would be great if you could give it a try. I want to make sure
> that this patch can fix the problem. It looks like there has the same
> problem in ext3. So if this patch is fine, I will generate a patch for
> ext3 file system.
Seems to fix the bug for me, both with your test case and also with trinity
runs, so...
Tested-by: Darrick J. Wong <darrick.wong@...cle.com>
--D
>
> Thanks,
> - Zheng
>
> From: Zheng Liu <wenqing.lz@...bao.com>
>
> When we try to open a file with O_TMPFILE flag, we will trigger a bug.
> The root cause is that in ext4_orphan_add() we check ->i_nlink == 0 and
> this check always fails because we set ->i_nlink = 1 in
> inode_init_always(). We can use the following program to trigger it:
>
> int main(int argc, char *argv[])
> {
> int fd;
>
> fd = open(argv[1], O_TMPFILE, 0666);
> if (fd < 0) {
> perror("open ");
> return -1;
> }
> close(fd);
> return 0;
> }
>
> The oops message looks like this:
>
> kernel BUG at fs/ext4/namei.c:2572!
> invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
> Modules linked in: dlci bridge stp hidp cmtp kernelcapi l2tp_ppp l2tp_netlink l2tp_core sctp libcrc32c rfcomm tun fuse nfnetli
> nk can_raw ipt_ULOG can_bcm x25 scsi_transport_iscsi ipx p8023 p8022 appletalk phonet psnap vmw_vsock_vmci_transport af_key vmw_vmci rose vsock atm can netrom ax25 af_rxrpc ir
> da pppoe pppox ppp_generic slhc bluetooth nfc rfkill rds caif_socket caif crc_ccitt af_802154 llc2 llc snd_hda_codec_realtek snd_hda_intel snd_hda_codec serio_raw snd_pcm pcsp
> kr edac_core snd_page_alloc snd_timer snd soundcore r8169 mii sr_mod cdrom pata_atiixp radeon backlight drm_kms_helper ttm
> CPU: 1 PID: 1812571 Comm: trinity-child2 Not tainted 3.11.0-rc1+ #12
> Hardware name: Gigabyte Technology Co., Ltd. GA-MA78GM-S2H/GA-MA78GM-S2H, BIOS F12a 04/23/2010
> task: ffff88007dfe69a0 ti: ffff88010f7b6000 task.ti: ffff88010f7b6000
> RIP: 0010:[<ffffffff8125ce69>] [<ffffffff8125ce69>] ext4_orphan_add+0x299/0x2b0
> RSP: 0018:ffff88010f7b7cf8 EFLAGS: 00010202
> RAX: 0000000000000000 RBX: ffff8800966d3020 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: ffff88007dfe70b8 RDI: 0000000000000001
> RBP: ffff88010f7b7d40 R08: ffff880126a3c4e0 R09: ffff88010f7b7ca0
> R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801271fd668
> R13: ffff8800966d2f78 R14: ffff88011d7089f0 R15: ffff88007dfe69a0
> FS: 00007f70441a3740(0000) GS:ffff88012a800000(0000) knlGS:00000000f77c96c0
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000002834000 CR3: 0000000107964000 CR4: 00000000000007e0
> DR0: 0000000000780000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
> Stack:
> 0000000000002000 00000020810b6dde 0000000000000000 ffff88011d46db00
> ffff8800966d3020 ffff88011d7089f0 ffff88009c7f4c10 ffff88010f7b7f2c
> ffff88007dfe69a0 ffff88010f7b7da8 ffffffff8125cfac ffff880100000004
> Call Trace:
> [<ffffffff8125cfac>] ext4_tmpfile+0x12c/0x180
> [<ffffffff811cba78>] path_openat+0x238/0x700
> [<ffffffff8100afc4>] ? native_sched_clock+0x24/0x80
> [<ffffffff811cc647>] do_filp_open+0x47/0xa0
> [<ffffffff811db73f>] ? __alloc_fd+0xaf/0x200
> [<ffffffff811ba2e4>] do_sys_open+0x124/0x210
> [<ffffffff81010725>] ? syscall_trace_enter+0x25/0x290
> [<ffffffff811ba3ee>] SyS_open+0x1e/0x20
> [<ffffffff816ca8d4>] tracesys+0xdd/0xe2
> [<ffffffff81001001>] ? start_thread_common.constprop.6+0x1/0xa0
> Code: 04 00 00 00 89 04 24 31 c0 e8 c4 77 04 00 e9 43 fe ff ff 66 25 00 d0 66 3d 00 80 0f 84 0e fe ff ff 83 7b 48 00 0f 84 04 fe ff ff <0f> 0b 49 8b 8c 24 50 07 00 00 e9 88 fe ff ff 0f 1f 84 00 00 00
>
> Here we couldn't call clear_nlink() directly because in d_tmpfile() we
> will call inode_dec_link_count() to decrease ->i_nlink. So this commit
> tries to call d_tmpfile() before ext4_orphan_add() to fix this problem.
>
> Reported-by: Dave Jones <davej@...hat.com>
> Signed-off-by: Zheng Liu <wenqing.lz@...bao.com>
> Cc: "Theodore Ts'o" <tytso@....edu>
> Cc: Al Viro <viro@...iv.linux.org.uk>
> ---
> fs/ext4/namei.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
> index 234b834..35f55a0 100644
> --- a/fs/ext4/namei.c
> +++ b/fs/ext4/namei.c
> @@ -2316,11 +2316,11 @@ retry:
> inode->i_op = &ext4_file_inode_operations;
> inode->i_fop = &ext4_file_operations;
> ext4_set_aops(inode);
> + d_tmpfile(dentry, inode);
> err = ext4_orphan_add(handle, inode);
> if (err)
> goto err_drop_inode;
> mark_inode_dirty(inode);
> - d_tmpfile(dentry, inode);
> unlock_new_inode(inode);
> }
> if (handle)
> --
> 1.7.9.7
>
> --
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