Public bug reported: I have a file located on ext4 mounted with "dax". When I call mmap on that file with protection flag different than PROT_NONE and pass the returned address to mprotect(..., PROT_NONE) it fails with: mprotect: Permission denied
This bug affects PMDK (https://github.com/pmem/pmdk) and seems to be Ubuntu kernel-specific. Problem was observer on kernel 4.15.0-36-generic and 4.15.0-34-generic Below is a code which can be used to reproduce the issue. #include <sys/stat.h> #include <sys/types.h> #include <sys/mman.h> #include <stdlib.h> #include <stdio.h> #include <fcntl.h> int main(int argc, char *argv[]) { if (argc < 3) { fprintf(stderr, "usage %s file size\n", argv[0]); return 1; } int size = atoi(argv[2]); int fd = open(argv[1], O_RDWR); if (fd < 0) { perror("open"); return 1; } void *addr = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); if (addr == MAP_FAILED) { perror("mmap"); return 1; } if(mprotect(addr, size, PROT_NONE)) { perror("mprotect"); return 1; } return 0; } ** Affects: ubuntu Importance: Undecided Status: New -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1799237 Title: mprotect fails on ext4 with dax To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+bug/1799237/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
