Re: [PATCH] ext4: fix a bug when we try to open a file withO_TMPFILE flag

[Darrick J. Wong]

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@xxxxxxxxxx>

--D

> 
> Thanks,
> 						- Zheng
> 
> From: Zheng Liu <wenqing.lz@xxxxxxxxxx>
> 
> 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@xxxxxxxxxx>
> Signed-off-by: Zheng Liu <wenqing.lz@xxxxxxxxxx>
> Cc: "Theodore Ts'o" <tytso@xxxxxxx>
> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> ---
>  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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