On 11/6/21 22:46, Ajay Garg wrote:
Actually, on further thoughts, even David's solution will require an extra check, if -E2BIG is returned. So, I guess the solution suggested by me looks the best (https://lore.kernel.org/linux-serial/868025b485b94480ad17d0ec971b3ee9@xxxxxxxxxxxxxxxx/T/#m1c4aaa4347b02fd4c11ce611ff5029fcb71c37a1) : 1. == Do not use the return value from strlcpy. == len = strlcpy(kbs, func_table[kb_func] ? : "", len); => strlcpy(kbs, func_table[kb_func] ? : "", len); 2. == Calculate the actual length of kbs, add 1, and then copy those many bytes to user-buffer == ret = copy_to_user(user_kdgkb->kb_string, kbs, len + 1) ? -EFAULT : 0; => ret = copy_to_user(user_kdgkb->kb_string, kbs, strlen(kbs) + 1) ? -EFAULT : 0;
But isn't strlen(kbs) is guaranteed to be equal to strlcpy() return value in this case? As I said in previous emails, strlen(func_table[kb_func]) < sizeof(user_kdgkb->kb_string) by design of this function.
Do we need extra strlen() call here? Let's see what more experienced people think about it :)
With regards, Pavel Skripkin
