Messages in this thread | | | Subject | RE: CLONE_NEWNS and bind mounts to make "chroot" jail | Date | Sun, 2 Mar 2008 22:56:40 -0800 | From | "Leibowitz, Michael" <> |
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If I understand correctly, the following should accomplish what I'm looking for. However, pivot_root gives me EBUSY. I played around with moving the mount --bind /jail /jail to before the unshared, as well as making old_root a bind mount to itself. However, pivot_root always seems to fail. Is there something obvious that I'm doing wrong? The following is my test code (error checking has been removed for clarity, except for pivot_root).
char *newargv[]= { "sh", NULL };
chdir("/jail"); unshare(CLONE_NEWNS)); mount("/jail", "/jail", NULL, MS_BIND, NULL)); mount("/bin", "bin", NULL, MS_BIND, NULL)); mount("/usr", "usr", NULL, MS_BIND, NULL)); mount("/lib", "lib", NULL, MS_BIND, NULL)); if (pivot_root(".", "old_root")) perror("pivot_root . old_root"); exec("./bash-static"); /* copied to /jail prior to running */
Thanks.
>Serge replies: [snip...snip] >Try a few more things. Since you had entered /jail, you can view '/' by >looking at .. . But if you look at /, you dereference your >task->fsroot. You never changed that, so it points to the original >mount. If however you 'ls ..', you should see your 'jail' directory. >However it won't have the /bin and /lib mounted because you didn't > mount --rbind /jail / >What you really want to do is > mount --bind /jail /jail >to make sure it's a mountpoint, then set up the new /jail using bind >mounts like you're doing (and likely some rbinds in some places), then >use pivot_root() to change your root. Then umount2("/old_root", >MNT_DETACH). > >-serge
-- Michael Leibowitz Software Engineer, UMG Intel Corporation michael.leibowitz at intel.com
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