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    Subject[PATCH 16/32] staging: gasket: always allow root open for write
    Date
    From: Todd Poynor <toddpoynor@google.com>

    Always allow root to open device for writing.

    Drop special-casing of ioctl permissions for root vs. owner.

    Reported-by: Dmitry Torokhov <dtor@chromium.org>
    Signed-off-by: Zhongze Hu <frankhu@chromium.org>
    Signed-off-by: Todd Poynor <toddpoynor@google.com>
    ---
    drivers/staging/gasket/apex_driver.c | 9 +--------
    drivers/staging/gasket/gasket_core.c | 8 +++++---
    drivers/staging/gasket/gasket_ioctl.c | 19 ++++++++-----------
    3 files changed, 14 insertions(+), 22 deletions(-)

    diff --git a/drivers/staging/gasket/apex_driver.c b/drivers/staging/gasket/apex_driver.c
    index 3a83c3d4d5561..612b3ab803196 100644
    --- a/drivers/staging/gasket/apex_driver.c
    +++ b/drivers/staging/gasket/apex_driver.c
    @@ -629,14 +629,7 @@ static bool is_gcb_in_reset(struct gasket_dev *gasket_dev)
    */
    static uint apex_ioctl_check_permissions(struct file *filp, uint cmd)
    {
    - struct gasket_dev *gasket_dev = filp->private_data;
    - int root = capable(CAP_SYS_ADMIN);
    - int is_owner = gasket_dev->dev_info.ownership.is_owned &&
    - current->tgid == gasket_dev->dev_info.ownership.owner;
    -
    - if (root || is_owner)
    - return 1;
    - return 0;
    + return !!(filp->f_mode & FMODE_WRITE);
    }

    /*
    diff --git a/drivers/staging/gasket/gasket_core.c b/drivers/staging/gasket/gasket_core.c
    index 0d5ba7359af73..947b4fcc76970 100644
    --- a/drivers/staging/gasket/gasket_core.c
    +++ b/drivers/staging/gasket/gasket_core.c
    @@ -1085,6 +1085,7 @@ static int gasket_open(struct inode *inode, struct file *filp)
    char task_name[TASK_COMM_LEN];
    struct gasket_cdev_info *dev_info =
    container_of(inode->i_cdev, struct gasket_cdev_info, cdev);
    + int is_root = capable(CAP_SYS_ADMIN);

    gasket_dev = dev_info->gasket_dev_ptr;
    driver_desc = gasket_dev->internal_desc->driver_desc;
    @@ -1098,7 +1099,7 @@ static int gasket_open(struct inode *inode, struct file *filp)
    "Attempting to open with tgid %u (%s) (f_mode: 0%03o, "
    "fmode_write: %d is_root: %u)",
    current->tgid, task_name, filp->f_mode,
    - (filp->f_mode & FMODE_WRITE), capable(CAP_SYS_ADMIN));
    + (filp->f_mode & FMODE_WRITE), is_root);

    /* Always allow non-writing accesses. */
    if (!(filp->f_mode & FMODE_WRITE)) {
    @@ -1112,8 +1113,9 @@ static int gasket_open(struct inode *inode, struct file *filp)
    gasket_dev, "Current owner open count (owning tgid %u): %d.",
    ownership->owner, ownership->write_open_count);

    - /* Opening a node owned by another TGID is an error (even root.) */
    - if (ownership->is_owned && ownership->owner != current->tgid) {
    + /* Opening a node owned by another TGID is an error (unless root) */
    + if (ownership->is_owned && ownership->owner != current->tgid &&
    + !is_root) {
    gasket_log_error(
    gasket_dev,
    "Process %u is opening a node held by %u.",
    diff --git a/drivers/staging/gasket/gasket_ioctl.c b/drivers/staging/gasket/gasket_ioctl.c
    index 0c2f85cf54480..d0fa05b8bf1d3 100644
    --- a/drivers/staging/gasket/gasket_ioctl.c
    +++ b/drivers/staging/gasket/gasket_ioctl.c
    @@ -171,7 +171,7 @@ long gasket_is_supported_ioctl(uint cmd)
    */
    static uint gasket_ioctl_check_permissions(struct file *filp, uint cmd)
    {
    - uint alive, root, device_owner;
    + uint alive;
    fmode_t read, write;
    struct gasket_dev *gasket_dev = (struct gasket_dev *)filp->private_data;

    @@ -183,33 +183,30 @@ static uint gasket_ioctl_check_permissions(struct file *filp, uint cmd)
    alive, gasket_dev->status);
    }

    - root = capable(CAP_SYS_ADMIN);
    - read = filp->f_mode & FMODE_READ;
    - write = filp->f_mode & FMODE_WRITE;
    - device_owner = (gasket_dev->dev_info.ownership.is_owned &&
    - current->tgid == gasket_dev->dev_info.ownership.owner);
    + read = !!(filp->f_mode & FMODE_READ);
    + write = !!(filp->f_mode & FMODE_WRITE);

    switch (cmd) {
    case GASKET_IOCTL_RESET:
    case GASKET_IOCTL_CLEAR_INTERRUPT_COUNTS:
    - return root || (write && device_owner);
    + return write;

    case GASKET_IOCTL_PAGE_TABLE_SIZE:
    case GASKET_IOCTL_SIMPLE_PAGE_TABLE_SIZE:
    case GASKET_IOCTL_NUMBER_PAGE_TABLES:
    - return root || read;
    + return read;

    case GASKET_IOCTL_PARTITION_PAGE_TABLE:
    case GASKET_IOCTL_CONFIG_COHERENT_ALLOCATOR:
    - return alive && (root || (write && device_owner));
    + return alive && write;

    case GASKET_IOCTL_MAP_BUFFER:
    case GASKET_IOCTL_UNMAP_BUFFER:
    - return alive && (root || (write && device_owner));
    + return alive && write;

    case GASKET_IOCTL_CLEAR_EVENTFD:
    case GASKET_IOCTL_SET_EVENTFD:
    - return alive && (root || (write && device_owner));
    + return alive && write;
    }

    return 0; /* unknown permissions */
    --
    2.18.0.203.gfac676dfb9-goog
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