• Zheng Liu's avatar
    ext4: fix a BUG when opening a file with O_TMPFILE flag · e94bd349
    Zheng Liu authored
    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: default avatarDave Jones <davej@redhat.com>
    Signed-off-by: default avatarZheng Liu <wenqing.lz@taobao.com>
    Tested-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
    Tested-by: default avatarDave Jones <davej@redhat.com>
    Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
    Acked-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
    e94bd349
namei.c 85.7 KB