From: Kees Cook
Sent: 16 June 2020 04:25
For both pidfd and seccomp, the __user pointer is not used. Update __fd_install_received() to make writing to ufd optional. (ufd itself cannot checked for NULL because this changes the SCM_RIGHTS interface behavior.) In these cases, the new fd needs to be returned on success. Update the existing callers to handle it. Add new wrapper fd_install_received() for pidfd and seccomp that does not use the ufd argument.
...>
static inline int fd_install_received_user(struct file *file, int __user *ufd, unsigned int o_flags) {
- return __fd_install_received(file, ufd, o_flags);
- return __fd_install_received(file, true, ufd, o_flags);
+}
Can you get rid of the 'return user' parameter by adding if (!ufd) return -EFAULT; to the above wrapper, then checking for NULL in the function?
Or does that do the wrong horrid things in the fail path?
David
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