diff options
| -rw-r--r-- | configure.ac | 1 | ||||
| -rw-r--r-- | src/libstore/build.cc | 35 |
2 files changed, 29 insertions, 7 deletions
diff --git a/configure.ac b/configure.ac index be77975bd..756b2f227 100644 --- a/configure.ac +++ b/configure.ac @@ -87,6 +87,7 @@ AC_CHECK_HEADERS([sys/mount.h], [], [], # include <sys/param.h> # endif ]) +AC_CHECK_HEADERS([sys/syscall.h]) # Check for lutimes, optionally used for changing the mtime of diff --git a/src/libstore/build.cc b/src/libstore/build.cc index 259324734..4841c9373 100644 --- a/src/libstore/build.cc +++ b/src/libstore/build.cc @@ -38,6 +38,9 @@ #if HAVE_SYS_MOUNT_H #include <sys/mount.h> #endif +#if HAVE_SYS_SYSCALL_H +#include <sys/syscall.h> +#endif #if HAVE_SCHED_H #include <sched.h> #endif @@ -48,7 +51,7 @@ #include <linux/fs.h> #endif -#define CHROOT_ENABLED HAVE_CHROOT && HAVE_UNSHARE && HAVE_SYS_MOUNT_H && defined(MS_BIND) && defined(MS_PRIVATE) && defined(CLONE_NEWNS) +#define CHROOT_ENABLED HAVE_CHROOT && HAVE_UNSHARE && HAVE_SYS_MOUNT_H && defined(MS_BIND) && defined(MS_PRIVATE) && defined(CLONE_NEWNS) && defined(SYS_pivot_root) /* chroot-like behavior from Apple's sandbox */ #if __APPLE__ @@ -2059,6 +2062,11 @@ void DerivationGoal::runChild() throw SysError(format("unable to make filesystem ‘%1%’ private") % fs); } + /* Bind-mount chroot directory to itself, to treat it as a + different filesystem from /, as needed for pivot_root. */ + if (mount(chrootRootDir.c_str(), chrootRootDir.c_str(), 0, MS_BIND, 0) == -1) + throw SysError(format("unable to bind mount ‘%1%’") % chrootRootDir); + /* Set up a nearly empty /dev, unless the user asked to bind-mount the host /dev. */ if (dirsInChroot.find("/dev") == dirsInChroot.end()) { @@ -2130,13 +2138,26 @@ void DerivationGoal::runChild() chmod_(chrootRootDir + "/dev/pts/ptmx", 0666); } - /* Do the chroot(). Below we do a chdir() to the - temporary build directory to make sure the current - directory is in the chroot. (Actually the order - doesn't matter, since due to the bind mount tmpDir and - tmpRootDit/tmpDir are the same directories.) */ - if (chroot(chrootRootDir.c_str()) == -1) + /* Do the chroot(). */ + if (chdir(chrootRootDir.c_str()) == -1) + throw SysError(format("cannot change directory to ‘%1%’") % chrootRootDir); + + if (mkdir("real-root", 0) == -1) + throw SysError("cannot create real-root directory"); + +#define pivot_root(new_root, put_old) (syscall(SYS_pivot_root, new_root, put_old)) + if (pivot_root(".", "real-root") == -1) + throw SysError(format("cannot pivot old root directory onto ‘%1%’") % (chrootRootDir + "/real-root")); +#undef pivot_root + + if (chroot(".") == -1) throw SysError(format("cannot change root directory to ‘%1%’") % chrootRootDir); + + if (umount2("real-root", MNT_DETACH) == -1) + throw SysError("cannot unmount real root filesystem"); + + if (rmdir("real-root") == -1) + throw SysError("cannot remove real-root directory"); } #endif |