Re: [syzbot] [mm?] WARNING in __page_table_check_ptes_set

[David Hildenbrand]

> > commit f369b07c861435bd812a9d14493f71b34132ed6f
> > Author: Peter Xu <peterx@xxxxxxxxxx>
> > Date:   Thu Aug 11 16:13:40 2022 -0400
> >
> >      mm/uffd: reset write protection when unregister with wp-mode
> >
> >
> > close should behave just like unregister.
> >
> >
> > Simplified+readable reproducer:
> >
> > #define _GNU_SOURCE
> >
> > #include <stdint.h>
> > #include <fcntl.h>
> > #include <sys/syscall.h>
> > #include <sys/mman.h>
> > #include <sys/types.h>
> > #include <sys/ioctl.h>
> > #include <linux/userfaultfd.h>
> > #include <unistd.h>
> >
> > int main(void)
> > {
> >          void *src = mmap(0, 4096, PROT_READ, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
> >          void *dst = mmap(0, 4096, PROT_READ, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
> >          struct uffdio_register uffdio_register = {};
> >          struct uffdio_copy uffdio_copy = {};
> >          struct uffdio_api uffdio_api = {};
> >          int uffd;
> >
> >          uffd = syscall(SYS_userfaultfd, O_CLOEXEC | O_NONBLOCK | UFFD_USER_MODE_ONLY);
> >          uffdio_api.api = UFFD_API;
> >          ioctl(uffd, UFFDIO_API, &uffdio_api);
> >
> >          uffdio_register.range.start = (uintptr_t)dst;
> >          uffdio_register.range.len = 4096;
> >          uffdio_register.mode = UFFDIO_REGISTER_MODE_WP;
> >          ioctl(uffd, UFFDIO_REGISTER, &uffdio_register);
> >
> >          uffdio_copy.dst = (uintptr_t)dst;
> >          uffdio_copy.src = (uintptr_t)src;
> >          uffdio_copy.len = 4096;
> >          uffdio_copy.mode = UFFDIO_COPY_MODE_DONTWAKE|UFFDIO_COPY_MODE_WP;
> >          ioctl(uffd, UFFDIO_COPY, &uffdio_copy);
> >
> >          close(uffd);
> >
> >          mprotect(dst, 4096, PROT_READ|PROT_WRITE);
> >          return 0;
> > }
>
> Thanks, I'll post a patch.
>
> PS: next time feel free to try "strace ./reproducer", it'll do the
> translations and I found it handy to work with syzbot.

Cool, was not aware that it would do that amount of translation!

--
Cheers,

David / dhildenb