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    Subject[PATCH AUTOSEL 4.19 039/192] cifs: Fix NULL pointer dereference of devname
    Date
    From: Yao Liu <yotta.liu@ucloud.cn>

    [ Upstream commit 68e2672f8fbd1e04982b8d2798dd318bf2515dd2 ]

    There is a NULL pointer dereference of devname in strspn()

    The oops looks something like:

    CIFS: Attempting to mount (null)
    BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
    ...
    RIP: 0010:strspn+0x0/0x50
    ...
    Call Trace:
    ? cifs_parse_mount_options+0x222/0x1710 [cifs]
    ? cifs_get_volume_info+0x2f/0x80 [cifs]
    cifs_setup_volume_info+0x20/0x190 [cifs]
    cifs_get_volume_info+0x50/0x80 [cifs]
    cifs_smb3_do_mount+0x59/0x630 [cifs]
    ? ida_alloc_range+0x34b/0x3d0
    cifs_do_mount+0x11/0x20 [cifs]
    mount_fs+0x52/0x170
    vfs_kern_mount+0x6b/0x170
    do_mount+0x216/0xdc0
    ksys_mount+0x83/0xd0
    __x64_sys_mount+0x25/0x30
    do_syscall_64+0x65/0x220
    entry_SYSCALL_64_after_hwframe+0x49/0xbe

    Fix this by adding a NULL check on devname in cifs_parse_devname()

    Signed-off-by: Yao Liu <yotta.liu@ucloud.cn>
    Signed-off-by: Steve French <stfrench@microsoft.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    fs/cifs/connect.c | 5 +++++
    1 file changed, 5 insertions(+)

    diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
    index a5ea742654aa..f31339db45fd 100644
    --- a/fs/cifs/connect.c
    +++ b/fs/cifs/connect.c
    @@ -1347,6 +1347,11 @@ cifs_parse_devname(const char *devname, struct smb_vol *vol)
    const char *delims = "/\\";
    size_t len;

    + if (unlikely(!devname || !*devname)) {
    + cifs_dbg(VFS, "Device name not specified.\n");
    + return -EINVAL;
    + }
    +
    /* make sure we have a valid UNC double delimiter prefix */
    len = strspn(devname, delims);
    if (len != 2)
    --
    2.19.1
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