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    Subject[PATCH AUTOSEL 4.9 20/32] nfs: Fix NULL pointer dereference of dev_name
    Date
    From: Yao Liu <yotta.liu@ucloud.cn>

    [ Upstream commit 80ff00172407e0aad4b10b94ef0816fc3e7813cb ]

    There is a NULL pointer dereference of dev_name in nfs_parse_devname()

    The oops looks something like:

    BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
    ...
    RIP: 0010:nfs_fs_mount+0x3b6/0xc20 [nfs]
    ...
    Call Trace:
    ? ida_alloc_range+0x34b/0x3d0
    ? nfs_clone_super+0x80/0x80 [nfs]
    ? nfs_free_parsed_mount_data+0x60/0x60 [nfs]
    mount_fs+0x52/0x170
    ? __init_waitqueue_head+0x3b/0x50
    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 dev_name

    Signed-off-by: Yao Liu <yotta.liu@ucloud.cn>
    Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    fs/nfs/super.c | 5 +++++
    1 file changed, 5 insertions(+)

    diff --git a/fs/nfs/super.c b/fs/nfs/super.c
    index 2fdb8f5a7b69d..841b5664098f9 100644
    --- a/fs/nfs/super.c
    +++ b/fs/nfs/super.c
    @@ -1904,6 +1904,11 @@ static int nfs_parse_devname(const char *dev_name,
    size_t len;
    char *end;

    + if (unlikely(!dev_name || !*dev_name)) {
    + dfprintk(MOUNT, "NFS: device name not specified\n");
    + return -EINVAL;
    + }
    +
    /* Is the host name protected with square brakcets? */
    if (*dev_name == '[') {
    end = strchr(++dev_name, ']');
    --
    2.19.1
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