I have created a file using
debugfs API inside
/sys/kernel/debug/test/testFile. I have created the file with mode set to
444, so it is now read only.
Now I have essentially followed this tutorial in creating this
debugfs file. And for this file both
write are define. Moreover, concretely, I create file using this:
debugfs_create_file("testFile", 444, pDebugfs, NULL, &debugfs_fops)
File is successfully created and I can easily read from it by
cat ... but why I can write to it too even though I can explicitly created as
read only. I am logged in as root. Why is that? Should not it not allow me to write to it?
ls -l results:
-r--r--r-- 1 root root 0 جون 28 15:27 /sys/kernel/debug/test/testFile
Now, you may argue that since I am root, I can write to any file. Well, then if you search
let's access blob file on the page, the OP cannot write to blob file, even though as root, because it is read only. Why is that?