• Erick Archer's avatar
    Bluetooth: hci_core: Prefer struct_size over open coded arithmetic · 8f7dfe17
    Erick Archer authored
    This is an effort to get rid of all multiplications from allocation
    functions in order to prevent integer overflows [1][2].
    
    As the "dl" variable is a pointer to "struct hci_dev_list_req" and this
    structure ends in a flexible array:
    
    struct hci_dev_list_req {
    	[...]
    	struct hci_dev_req dev_req[];	/* hci_dev_req structures */
    };
    
    the preferred way in the kernel is to use the struct_size() helper to
    do the arithmetic instead of the calculation "size + count * size" in
    the kzalloc() and copy_to_user() functions.
    
    At the same time, prepare for the coming implementation by GCC and Clang
    of the __counted_by attribute. Flexible array members annotated with
    __counted_by can have their accesses bounds-checked at run-time via
    CONFIG_UBSAN_BOUNDS (for array indexing) and CONFIG_FORTIFY_SOURCE (for
    strcpy/memcpy-family functions).
    
    In this case, it is important to note that the logic needs a little
    refactoring to ensure that the "dev_num" member is initialized before
    the first access to the flex array. Specifically, add the assignment
    before the list_for_each_entry() loop.
    
    Also remove the "size" variable as it is no longer needed.
    
    This way, the code is more readable and safer.
    
    This code was detected with the help of Coccinelle, and audited and
    modified manually.
    
    Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [1]
    Link: https://github.com/KSPP/linux/issues/160 [2]
    Reviewed-by: default avatarKees Cook <keescook@chromium.org>
    Signed-off-by: default avatarErick Archer <erick.archer@outlook.com>
    Signed-off-by: default avatarLuiz Augusto von Dentz <luiz.von.dentz@intel.com>
    8f7dfe17
hci_core.c 94 KB