On 13/6/23 17:59, Greg KH wrote:
On Mon, Jun 12, 2023 at 09:51:38PM +0000, Avadhut Naik wrote:/** - * debugfs_create_blob - create a debugfs file that is used to read a binary blob + * debugfs_create_blob - create a debugfs file that is used to read and write + * a binary blob * @name: a pointer to a string containing the name of the file to create. - * @mode: the read permission that the file should have (other permissions are - * masked out) + * @mode: the permission that the file should have * @parent: a pointer to the parent dentry for this file. This should be a * directory dentry if set. If this parameter is %NULL, then the * file will be created in the root of the debugfs filesystem. @@ -992,7 +1010,7 @@ static const struct file_operations fops_blob = { * * This function creates a file in debugfs with the given name that exports * @blob->data as a binary blob. If the @mode variable is so set it can be - * read from. Writing is not supported. + * read from and written to. * * This function will return a pointer to a dentry if it succeeds. This * pointer must be passed to the debugfs_remove() function when the file is @@ -1007,7 +1025,7 @@ struct dentry *debugfs_create_blob(const char *name, umode_t mode, struct dentry *parent, struct debugfs_blob_wrapper *blob) { - return debugfs_create_file_unsafe(name, mode & 0444, parent, blob, &fops_blob); + return debugfs_create_file_unsafe(name, mode, parent, blob, &fops_blob);Have you audited all calls to this function to verify that you haven't just turned on write access to some debugfs files?
I just did, it is one of S_IRUGO/S_IRUSR/0444/0400/(S_IFREG | 0444). So we are quite safe here. Except (S_IFREG | 0444) in drivers/platform/chrome/cros_ec_debugfs.c which seems wrong as debugfs files are not regular files.
Why not rename this to debugfs_create_blob_wo() and then make a new debugfs_create_blob_rw() call to ensure that it all is ok?
It is already taking the mode for this purpose. imho just cros_ec_create_panicinfo()'s debugfs_create_blob("panicinfo", S_IFREG | 0444,...) needs fixing.
thanks, greg k-h
-- Alexey
