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    Subject[46/99] CIFS: Fixing to avoid invalid kfree() in cifs_get_tcp_session()
    2.6.31-stable review patch.  If anyone has any objections, please let us know.

    ------------------
    From: Steve French <sfrench@us.ibm.com>

    commit 8347a5cdd1422eea0470ed586274c7f29e274b47 upstream.

    trivial bug in fs/cifs/connect.c .
    The bug is caused by fail of extract_hostname()
    when mounting cifs file system.

    This is the situation when I noticed this bug.

    % sudo mount -t cifs //192.168.10.208 mountpoint -o options...

    Then my kernel says,

    [ 1461.807776] ------------[ cut here ]------------
    [ 1461.807781] kernel BUG at mm/slab.c:521!
    [ 1461.807784] invalid opcode: 0000 [#2] PREEMPT SMP
    [ 1461.807790] last sysfs file:
    /sys/devices/pci0000:00/0000:00:1e.0/0000:09:02.0/resource
    [ 1461.807793] CPU 0
    [ 1461.807796] Modules linked in: nls_iso8859_1 usbhid sbp2 uhci_hcd
    ehci_hcd i2c_i801 ohci1394 ieee1394 psmouse serio_raw pcspkr sky2 usbcore
    evdev
    [ 1461.807816] Pid: 3446, comm: mount Tainted: G D 2.6.32-rc2-vanilla
    [ 1461.807820] RIP: 0010:[<ffffffff810b888e>] [<ffffffff810b888e>]
    kfree+0x63/0x156
    [ 1461.807829] RSP: 0018:ffff8800b4f7fbb8 EFLAGS: 00010046
    [ 1461.807832] RAX: ffffea00033fff98 RBX: ffff8800afbae7e2 RCX:
    0000000000000000
    [ 1461.807836] RDX: ffffea0000000000 RSI: 000000000000005c RDI:
    ffffffffffffffea
    [ 1461.807839] RBP: ffff8800b4f7fbf8 R08: 0000000000000001 R09:
    0000000000000000
    [ 1461.807842] R10: 0000000000000000 R11: ffff8800b4f7fbf8 R12:
    00000000ffffffea
    [ 1461.807845] R13: ffff8800afb23000 R14: ffff8800b4f87bc0 R15:
    ffffffffffffffea
    [ 1461.807849] FS: 00007f52b6f187c0(0000) GS:ffff880007600000(0000)
    knlGS:0000000000000000
    [ 1461.807852] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
    [ 1461.807855] CR2: 0000000000613000 CR3: 00000000af8f9000 CR4:
    00000000000006f0
    [ 1461.807858] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
    0000000000000000
    [ 1461.807861] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7:
    0000000000000400
    [ 1461.807865] Process mount (pid: 3446, threadinfo ffff8800b4f7e000, task
    ffff8800950e4380)
    [ 1461.807867] Stack:
    [ 1461.807869] 0000000000000202 0000000000000282 ffff8800b4f7fbf8
    ffff8800afbae7e2
    [ 1461.807876] <0> 00000000ffffffea ffff8800afb23000 ffff8800b4f87bc0
    ffff8800b4f7fc28
    [ 1461.807884] <0> ffff8800b4f7fcd8 ffffffff81159f6d ffffffff81147bc2
    ffffffff816bfb48
    [ 1461.807892] Call Trace:
    [ 1461.807899] [<ffffffff81159f6d>] cifs_get_tcp_session+0x440/0x44b
    [ 1461.807904] [<ffffffff81147bc2>] ? find_nls+0x1c/0xe9
    [ 1461.807909] [<ffffffff8115b889>] cifs_mount+0x16bc/0x2167
    [ 1461.807917] [<ffffffff814455bd>] ? _spin_unlock+0x30/0x4b
    [ 1461.807923] [<ffffffff81150da9>] cifs_get_sb+0xa5/0x1a8
    [ 1461.807928] [<ffffffff810c1b94>] vfs_kern_mount+0x56/0xc9
    [ 1461.807933] [<ffffffff810c1c64>] do_kern_mount+0x47/0xe7
    [ 1461.807938] [<ffffffff810d8632>] do_mount+0x712/0x775
    [ 1461.807943] [<ffffffff810d671f>] ? copy_mount_options+0xcf/0x132
    [ 1461.807948] [<ffffffff810d8714>] sys_mount+0x7f/0xbf
    [ 1461.807953] [<ffffffff8144509a>] ? lockdep_sys_exit_thunk+0x35/0x67
    [ 1461.807960] [<ffffffff81011cc2>] system_call_fastpath+0x16/0x1b
    [ 1461.807963] Code: 00 00 00 00 ea ff ff 48 c1 e8 0c 48 6b c0 68 48 01 d0
    66 83 38 00 79 04 48 8b 40 10 66 83 38 00 79 04 48 8b 40 10 80 38 00 78 04
    <0f> 0b eb fe 4c 8b 70 58 4c 89 ff 41 8b 76 4c e8 b8 49 fb ff e8
    [ 1461.808022] RIP [<ffffffff810b888e>] kfree+0x63/0x156
    [ 1461.808027] RSP <ffff8800b4f7fbb8>
    [ 1461.808031] ---[ end trace ffe26fcdc72c0ce4 ]---

    The reason of this bug is that the error handling code of
    cifs_get_tcp_session()
    calls kfree() when corresponding kmalloc() failed.
    (The kmalloc() is called by extract_hostname().)

    Signed-off-by: Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp>
    Reviewed-by: Jeff Layton <jlayton@redhat.com>
    Signed-off-by: Steve French <sfrench@us.ibm.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    fs/cifs/connect.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    --- a/fs/cifs/connect.c
    +++ b/fs/cifs/connect.c
    @@ -1556,7 +1556,8 @@ cifs_get_tcp_session(struct smb_vol *vol

    out_err:
    if (tcp_ses) {
    - kfree(tcp_ses->hostname);
    + if (!IS_ERR(tcp_ses->hostname))
    + kfree(tcp_ses->hostname);
    if (tcp_ses->ssocket)
    sock_release(tcp_ses->ssocket);
    kfree(tcp_ses);



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