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    Subject[ 46/68] eCryptfs: Fix lockdep warning in miscdev operations
    Date
    From: Greg KH <gregkh@linuxfoundation.org>

    3.0-stable review patch. If anyone has any objections, please let me know.

    ------------------

    From: Tyler Hicks <tyhicks@canonical.com>

    commit 60d65f1f07a7d81d3eb3b91fc13fca80f2fdbb12 upstream.

    Don't grab the daemon mutex while holding the message context mutex.
    Addresses this lockdep warning:

    ecryptfsd/2141 is trying to acquire lock:
    (&ecryptfs_msg_ctx_arr[i].mux){+.+.+.}, at: [<ffffffffa029c213>] ecryptfs_miscdev_read+0x143/0x470 [ecryptfs]

    but task is already holding lock:
    (&(*daemon)->mux){+.+...}, at: [<ffffffffa029c2ec>] ecryptfs_miscdev_read+0x21c/0x470 [ecryptfs]

    which lock already depends on the new lock.

    the existing dependency chain (in reverse order) is:

    -> #1 (&(*daemon)->mux){+.+...}:
    [<ffffffff810a3b8d>] lock_acquire+0x9d/0x220
    [<ffffffff8151c6da>] __mutex_lock_common+0x5a/0x4b0
    [<ffffffff8151cc64>] mutex_lock_nested+0x44/0x50
    [<ffffffffa029c5d7>] ecryptfs_send_miscdev+0x97/0x120 [ecryptfs]
    [<ffffffffa029b744>] ecryptfs_send_message+0x134/0x1e0 [ecryptfs]
    [<ffffffffa029a24e>] ecryptfs_generate_key_packet_set+0x2fe/0xa80 [ecryptfs]
    [<ffffffffa02960f8>] ecryptfs_write_metadata+0x108/0x250 [ecryptfs]
    [<ffffffffa0290f80>] ecryptfs_create+0x130/0x250 [ecryptfs]
    [<ffffffff811963a4>] vfs_create+0xb4/0x120
    [<ffffffff81197865>] do_last+0x8c5/0xa10
    [<ffffffff811998f9>] path_openat+0xd9/0x460
    [<ffffffff81199da2>] do_filp_open+0x42/0xa0
    [<ffffffff81187998>] do_sys_open+0xf8/0x1d0
    [<ffffffff81187a91>] sys_open+0x21/0x30
    [<ffffffff81527d69>] system_call_fastpath+0x16/0x1b

    -> #0 (&ecryptfs_msg_ctx_arr[i].mux){+.+.+.}:
    [<ffffffff810a3418>] __lock_acquire+0x1bf8/0x1c50
    [<ffffffff810a3b8d>] lock_acquire+0x9d/0x220
    [<ffffffff8151c6da>] __mutex_lock_common+0x5a/0x4b0
    [<ffffffff8151cc64>] mutex_lock_nested+0x44/0x50
    [<ffffffffa029c213>] ecryptfs_miscdev_read+0x143/0x470 [ecryptfs]
    [<ffffffff811887d3>] vfs_read+0xb3/0x180
    [<ffffffff811888ed>] sys_read+0x4d/0x90
    [<ffffffff81527d69>] system_call_fastpath+0x16/0x1b

    Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/ecryptfs/miscdev.c | 25 +++++++++++++------------
    1 file changed, 13 insertions(+), 12 deletions(-)

    --- a/fs/ecryptfs/miscdev.c
    +++ b/fs/ecryptfs/miscdev.c
    @@ -195,31 +195,32 @@ int ecryptfs_send_miscdev(char *data, si
    struct ecryptfs_msg_ctx *msg_ctx, u8 msg_type,
    u16 msg_flags, struct ecryptfs_daemon *daemon)
    {
    - int rc = 0;
    + struct ecryptfs_message *msg;

    - mutex_lock(&msg_ctx->mux);
    - msg_ctx->msg = kmalloc((sizeof(*msg_ctx->msg) + data_size),
    - GFP_KERNEL);
    - if (!msg_ctx->msg) {
    - rc = -ENOMEM;
    + msg = kmalloc((sizeof(*msg) + data_size), GFP_KERNEL);
    + if (!msg) {
    printk(KERN_ERR "%s: Out of memory whilst attempting "
    "to kmalloc(%zd, GFP_KERNEL)\n", __func__,
    - (sizeof(*msg_ctx->msg) + data_size));
    - goto out_unlock;
    + (sizeof(*msg) + data_size));
    + return -ENOMEM;
    }
    +
    + mutex_lock(&msg_ctx->mux);
    + msg_ctx->msg = msg;
    msg_ctx->msg->index = msg_ctx->index;
    msg_ctx->msg->data_len = data_size;
    msg_ctx->type = msg_type;
    memcpy(msg_ctx->msg->data, data, data_size);
    msg_ctx->msg_size = (sizeof(*msg_ctx->msg) + data_size);
    - mutex_lock(&daemon->mux);
    list_add_tail(&msg_ctx->daemon_out_list, &daemon->msg_ctx_out_queue);
    + mutex_unlock(&msg_ctx->mux);
    +
    + mutex_lock(&daemon->mux);
    daemon->num_queued_msg_ctx++;
    wake_up_interruptible(&daemon->wait);
    mutex_unlock(&daemon->mux);
    -out_unlock:
    - mutex_unlock(&msg_ctx->mux);
    - return rc;
    +
    + return 0;
    }

    /**



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