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Set up a minimal /dev in chroots

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Not bind-mounting the /dev from the host also solves the problem with
/dev/shm being a symlink to something not in the chroot.
This commit is contained in:
Eelco Dolstra 2014-02-27 23:17:53 +01:00
parent c9f6232304
commit 3fd01b171a
8 changed files with 40 additions and 17 deletions
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25
src/libstore/build.cc
View file

@ -2013,6 +2013,26 @@ void DerivationGoal::initChild()
throw SysError(format("unable to make filesystem `%1%' private") % fs);
}
/* Set up a nearly empty /dev, unless the user asked to
bind-mount the host /dev. */
if (dirsInChroot.find("/dev") == dirsInChroot.end()) {
createDirs(chrootRootDir + "/dev/shm");
Strings ss;
ss.push_back("/dev/full");
ss.push_back("/dev/kvm");
ss.push_back("/dev/null");
ss.push_back("/dev/ptmx");
ss.push_back("/dev/random");
ss.push_back("/dev/tty");
ss.push_back("/dev/urandom");
ss.push_back("/dev/zero");
foreach (Strings::iterator, i, ss) dirsInChroot[*i] = *i;
createSymlink("/proc/self/fd", chrootRootDir + "/dev/fd");
createSymlink("/proc/self/fd/0", chrootRootDir + "/dev/stdin");
createSymlink("/proc/self/fd/1", chrootRootDir + "/dev/stdout");
createSymlink("/proc/self/fd/2", chrootRootDir + "/dev/stderr");
}
/* Bind-mount all the directories from the "host"
filesystem that we want in the chroot
environment. */
@ -2042,9 +2062,8 @@ void DerivationGoal::initChild()
/* Mount a new tmpfs on /dev/shm to ensure that whatever
the builder puts in /dev/shm is cleaned up automatically. */
if (pathExists("/dev/shm"))
if (mount("none", (chrootRootDir + "/dev/shm").c_str(), "tmpfs", 0, 0) == -1)
throw SysError("mounting /dev/shm");
if (pathExists("/dev/shm") && mount("none", (chrootRootDir + "/dev/shm").c_str(), "tmpfs", 0, 0) == -1)
throw SysError("mounting /dev/shm");
/* Do the chroot(). Below we do a chdir() to the
temporary build directory to make sure the current

12
src/libstore/gc.cc
View file

@ -53,7 +53,7 @@ int LocalStore::openGCLock(LockType lockType)
}
void createSymlink(const Path & link, const Path & target)
static void makeSymlink(const Path & link, const Path & target)
{
/* Create directories up to `gcRoot'. */
createDirs(dirOf(link));
@ -61,9 +61,7 @@ void createSymlink(const Path & link, const Path & target)
/* Create the new symlink. */
Path tempLink = (format("%1%.tmp-%2%-%3%")
% link % getpid() % rand()).str();
if (symlink(target.c_str(), tempLink.c_str()) == -1)
throw SysError(format("symlinking `%1%' to `%2%'")
% tempLink % target);
createSymlink(target, tempLink);
/* Atomically replace the old one. */
if (rename(tempLink.c_str(), link.c_str()) == -1)
@ -83,7 +81,7 @@ void LocalStore::addIndirectRoot(const Path & path)
string hash = printHash32(hashString(htSHA1, path));
Path realRoot = canonPath((format("%1%/%2%/auto/%3%")
% settings.nixStateDir % gcRootsDir % hash).str());
createSymlink(realRoot, path);
makeSymlink(realRoot, path);
}
@ -104,7 +102,7 @@ Path addPermRoot(StoreAPI & store, const Path & _storePath,
point to the Nix store. */
if (pathExists(gcRoot) && (!isLink(gcRoot) || !isInStore(readLink(gcRoot))))
throw Error(format("cannot create symlink `%1%'; already exists") % gcRoot);
createSymlink(gcRoot, storePath);
makeSymlink(gcRoot, storePath);
store.addIndirectRoot(gcRoot);
}
@ -119,7 +117,7 @@ Path addPermRoot(StoreAPI & store, const Path & _storePath,
% gcRoot % rootsDir);
}
createSymlink(gcRoot, storePath);
makeSymlink(gcRoot, storePath);
}
/* Check that the root can be found by the garbage collector.

1
src/libstore/globals.cc
View file

@ -42,7 +42,6 @@ Settings::Settings()
useSubstitutes = true;
useChroot = false;
useSshSubstituter = false;
dirsInChroot.insert("/dev");
dirsInChroot.insert("/dev/pts");
impersonateLinux26 = false;
keepLog = true;

3
src/libstore/local-store.cc
View file

@ -243,8 +243,7 @@ LocalStore::LocalStore(bool reserveSpace)
Path gcRootsDir = settings.nixStateDir + "/gcroots";
if (!pathExists(gcRootsDir)) {
createDirs(gcRootsDir);
if (symlink(profilesDir.c_str(), (gcRootsDir + "/profiles").c_str()) == -1)
throw SysError(format("creating symlink to `%1%'") % profilesDir);
createSymlink(profilesDir, gcRootsDir + "/profiles");
}
checkStoreNotSymlink();

3
src/libutil/archive.cc
View file

@ -319,8 +319,7 @@ struct RestoreSink : ParseSink
void createSymlink(const Path & path, const string & target)
{
Path p = dstPath + path;
if (symlink(target.c_str(), p.c_str()) == -1)
throw SysError(format("creating symlink `%1%'") % p);
nix::createSymlink(target, p);
}
};

7
src/libutil/util.cc
View file

@ -386,6 +386,13 @@ Paths createDirs(const Path & path)
}
void createSymlink(const Path & target, const Path & link)
{
if (symlink(target.c_str(), link.c_str()))
throw SysError(format("creating symlink from `%1%' to `%2%'") % link % target);
}
LogType logType = ltPretty;
Verbosity verbosity = lvlInfo;

3
src/libutil/util.hh
View file

@ -93,6 +93,9 @@ Path createTempDir(const Path & tmpRoot = "", const Path & prefix = "nix",
list of created directories, in order of creation. */
Paths createDirs(const Path & path);
/* Create a symlink. */
void createSymlink(const Path & target, const Path & link);
template<class T, class A>
T singleton(const A & a)

3
src/nix-env/profiles.cc
View file

@ -118,8 +118,7 @@ void switchLink(Path link, Path target)
if (dirOf(target) == dirOf(link)) target = baseNameOf(target);
Path tmp = canonPath(dirOf(link) + "/.new_" + baseNameOf(link));
if (symlink(target.c_str(), tmp.c_str()) != 0)
throw SysError(format("creating symlink `%1%'") % tmp);
createSymlink(target, tmp);
/* The rename() system call is supposed to be essentially atomic
on Unix. That is, if we have links `current -> X' and
`new_current -> Y', and we rename new_current to current, a