diff options
Diffstat (limited to 'src/libstore/build.cc')
| -rw-r--r-- | src/libstore/build.cc | 179 |
1 files changed, 45 insertions, 134 deletions
diff --git a/src/libstore/build.cc b/src/libstore/build.cc index 6a3ba0f1cd6c..ab3a46aa8319 100644 --- a/src/libstore/build.cc +++ b/src/libstore/build.cc @@ -33,8 +33,11 @@ #if HAVE_SYS_MOUNT_H #include <sys/mount.h> #endif +#if HAVE_SCHED_H +#include <sched.h> +#endif -#define CHROOT_ENABLED HAVE_CHROOT && HAVE_SYS_MOUNT_H && defined(MS_BIND) +#define CHROOT_ENABLED HAVE_CHROOT && HAVE_SYS_MOUNT_H && defined(MS_BIND) && defined(CLONE_NEWNS) namespace nix { @@ -603,89 +606,6 @@ void deletePathWrapped(const Path & path) ////////////////////////////////////////////////////////////////////// -/* Helper RAII class for automatically unmounting bind-mounts in - chroots. */ -struct BindMount -{ - Path source, target; - Paths created; - - BindMount() - { - } - - BindMount(const Path & source, const Path & target) - { - bind(source, target); - } - - ~BindMount() - { - try { - unbind(); - } catch (...) { - ignoreException(); - } - } - - void bind(const Path & source, const Path & target) - { -#if CHROOT_ENABLED - debug(format("bind mounting `%1%' to `%2%'") % source % target); - - this->source = source; - this->target = target; - - created = createDirs(target); - - if (mount(source.c_str(), target.c_str(), "", MS_BIND, 0) == -1) - throw SysError(format("bind mount from `%1%' to `%2%' failed") % source % target); -#endif - } - - void unbind() - { -#if CHROOT_ENABLED - if (source == "") return; - - debug(format("unmount bind-mount `%1%'") % target); - - /* Urgh. Unmount sometimes doesn't succeed right away because - the mount point is still busy. It shouldn't be, because - we've killed all the build processes by now (at least when - using a build user; see the check in killUser()). But - maybe this is because those processes are still zombies and - are keeping some kernel structures busy (open files, - current directories, etc.). So retry a few times - (actually, a 1 second sleep is almost certainly enough for - the zombies to be cleaned up). */ - unsigned int tries = 0; - while (umount(target.c_str()) == -1) { - if (errno == EBUSY && ++tries < 10) { - printMsg(lvlError, format("unmounting `%1%' failed, retrying after 1 second...") % target); - sleep(1); - } - else - throw SysError(format("unmounting bind-mount `%1%' failed") % target); - } - - /* Get rid of the directories for the mount point created in - bind(). */ - for (Paths::reverse_iterator i = created.rbegin(); i != created.rend(); ++i) { - debug(format("deleting `%1%'") % *i); - if (remove(i->c_str()) == -1) - throw SysError(format("cannot unlink `%1%'") % *i); - } - - source = ""; -#endif - } -}; - - -////////////////////////////////////////////////////////////////////// - - class DerivationGoal : public Goal { private: @@ -729,17 +649,9 @@ private: /* Whether we're currently doing a chroot build. */ bool useChroot; - /* RAII objects to delete the chroot directory and its /tmp - directory. Don't change the order: autoDelChrootTmp has to be - deleted before autoDelChrootRoot. */ - boost::shared_ptr<AutoDelete> autoDelChrootRoot; - boost::shared_ptr<AutoDelete> autoDelChrootTmp; + /* RAII object to delete the chroot directory. */ + boost::shared_ptr<AutoDelete> autoDelChroot; - /* In chroot builds, the list of bind mounts currently active. - The destructor of BindMount will cause the binds to be - unmounted. Keep this *below* autoDelChroot* just to be safe! */ - list<boost::shared_ptr<BindMount> > bindMounts; - typedef void (DerivationGoal::*GoalState)(); GoalState state; @@ -1183,9 +1095,9 @@ void DerivationGoal::buildDone() deleteTmpDir(true); - /* In chroot builds, unmount the bind mounts ASAP. */ - bindMounts.clear(); /* the destructors will do the rest */ - + /* Delete the chroot (if we were using one). */ + autoDelChroot.reset(); /* this runs the destructor */ + /* Compute the FS closure of the outputs and register them as being valid. */ computeClosure(); @@ -1737,29 +1649,18 @@ void DerivationGoal::startBuilder() is somewhat pointless anyway. */ useChroot = queryBoolSetting("build-use-chroot", false); Path chrootRootDir; + Paths dirsInChroot; if (fixedOutput) useChroot = false; if (useChroot) { #if CHROOT_ENABLED /* Create a temporary directory in which we set up the chroot - environment using bind-mounts. - - !!! Bind mounts are potentially dangerous: if the user - cleans up his system by doing "rm -rf - /nix/var/nix/chroots/*", this will recurse into /nix/store - via the bind mounts (and potentially other parts of the - filesystem, depending on the setting of the - `build-chroot-dirs' option). */ + environment using bind-mounts. */ chrootRootDir = createTempDir(nixChrootsDir, "chroot-nix"); - /* Clean up the chroot directory automatically, but don't - recurse; that would be very very bad if the unmount of a - bind-mount fails. Instead BindMount::unbind() unmounts and - deletes exactly those directories that it created to - produce the mount point, so that after all the BindMount - destructors have run, chrootRootDir should be empty. */ - autoDelChrootRoot = boost::shared_ptr<AutoDelete>(new AutoDelete(chrootRootDir, false)); + /* Clean up the chroot directory automatically. */ + autoDelChroot = boost::shared_ptr<AutoDelete>(new AutoDelete(chrootRootDir)); printMsg(lvlChatty, format("setting up chroot environment in `%1%'") % chrootRootDir); @@ -1772,12 +1673,6 @@ void DerivationGoal::startBuilder() if (chmod(chrootTmpDir.c_str(), 01777) == -1) throw SysError("creating /tmp in the chroot"); - /* When deleting this, do recurse (the builder might have left - crap there). As long as nothing important is bind-mounted - under /tmp it's okay (and the bind-mounts are unmounted - before autoDelChrootTmp's destructor runs, anyway). */ - autoDelChrootTmp = boost::shared_ptr<AutoDelete>(new AutoDelete(chrootTmpDir)); - /* Bind-mount a user-configurable set of directories from the host file system. The `/dev/pts' directory must be mounted separately so that newly-created pseudo-terminals show @@ -1787,17 +1682,10 @@ void DerivationGoal::startBuilder() defaultDirs.push_back("/dev/pts"); defaultDirs.push_back("/proc"); - Paths dirsInChroot = querySetting("build-chroot-dirs", defaultDirs); + dirsInChroot = querySetting("build-chroot-dirs", defaultDirs); dirsInChroot.push_front(nixStore); dirsInChroot.push_front(tmpDir); - - /* Push BindMounts at the front of the list so that they get - unmounted in LIFO order. (!!! Does the C++ standard - guarantee that list elements are destroyed in order?) */ - for (Paths::iterator i = dirsInChroot.begin(); i != dirsInChroot.end(); ++i) - bindMounts.push_front(boost::shared_ptr<BindMount>(new BindMount(*i, chrootRootDir + *i))); - #else throw Error("chroot builds are not supported on this platform"); #endif @@ -1829,14 +1717,37 @@ void DerivationGoal::startBuilder() try { /* child */ #if CHROOT_ENABLED - /* If building in a chroot, do the chroot right away. - initChild() will 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 (useChroot && chroot(chrootRootDir.c_str()) == -1) - throw SysError(format("cannot change root directory to `%1%'") % chrootRootDir); + if (useChroot) { + /* Create our own mount namespace. This means that + all the bind mounts we do will only show up in this + process and its children, and will disappear + automatically when we're done. */ + if (unshare(CLONE_NEWNS) == -1) + throw SysError(format("cannot set up a private mount namespace")); + + /* Bind-mount all the directories from the "host" + filesystem that we want in the chroot + environment. */ + foreach (Paths::iterator, i, dirsInChroot) { + Path source = *i; + Path target = chrootRootDir + source; + printMsg(lvlError, format("bind mounting `%1%' to `%2%'") % source % target); + + createDirs(target); + + if (mount(source.c_str(), target.c_str(), "", MS_BIND, 0) == -1) + throw SysError(format("bind mount from `%1%' to `%2%' failed") % source % target); + } + + /* Do the chroot(). initChild() will 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) + throw SysError(format("cannot change root directory to `%1%'") % chrootRootDir); + } #endif initChild(); |