forked from lix-project/lix
makeStoreWritable: Use statvfs instead of /proc/self/mountinfo to find out if /nix/store is a read-only bind mount
/nix/store could be a read-only bind mount even if it is / in its own filesystem, so checking the 4th field in mountinfo is insufficient. Signed-off-by: Shea Levy <shea@shealevy.com>
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@ -106,6 +106,7 @@ AC_LANG_POP(C++)
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# Check for chroot support (requires chroot() and bind mounts).
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AC_CHECK_FUNCS([chroot])
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AC_CHECK_FUNCS([unshare])
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AC_CHECK_FUNCS([statvfs])
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AC_CHECK_HEADERS([sched.h])
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AC_CHECK_HEADERS([sys/param.h])
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AC_CHECK_HEADERS([sys/mount.h], [], [],
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@ -19,8 +19,9 @@
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#include <stdio.h>
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#include <time.h>
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#if HAVE_UNSHARE
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#if HAVE_UNSHARE && HAVE_STATVFS && HAVE_SYS_MOUNT_H
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#include <sched.h>
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#include <sys/statvfs.h>
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#include <sys/mount.h>
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#endif
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@ -434,30 +435,20 @@ void LocalStore::openDB(bool create)
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bind mount. So make the Nix store writable for this process. */
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void LocalStore::makeStoreWritable()
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{
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#if HAVE_UNSHARE
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#if HAVE_UNSHARE && HAVE_STATVFS && HAVE_SYS_MOUNT_H && defined(MS_BIND) && defined(MS_REMOUNT)
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if (getuid() != 0) return;
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if (!pathExists("/proc/self/mountinfo")) return;
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/* Check if /nix/store is a read-only bind mount. */
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bool found = false;
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Strings mounts = tokenizeString<Strings>(readFile("/proc/self/mountinfo", true), "\n");
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foreach (Strings::iterator, i, mounts) {
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vector<string> fields = tokenizeString<vector<string> >(*i, " ");
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if (fields.at(3) == "/" || fields.at(4) != settings.nixStore) continue;
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Strings options = tokenizeString<Strings>(fields.at(5), ",");
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if (std::find(options.begin(), options.end(), "ro") == options.end()) continue;
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found = true;
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break;
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struct statvfs stat;
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if (statvfs(settings.nixStore.c_str(), &stat) !=0)
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throw SysError("Getting info of nix store mountpoint");
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if (stat.f_flag & (ST_RDONLY | MS_BIND)) {
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if (unshare(CLONE_NEWNS) == -1)
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throw SysError("setting up a private mount namespace");
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if (mount(0, settings.nixStore.c_str(), 0, MS_REMOUNT | MS_BIND, 0) == -1)
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throw SysError(format("remounting %1% writable") % settings.nixStore);
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}
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if (!found) return;
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if (unshare(CLONE_NEWNS) == -1)
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throw SysError("setting up a private mount namespace");
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if (mount(0, settings.nixStore.c_str(), 0, MS_REMOUNT | MS_BIND, 0) == -1)
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throw SysError(format("remounting %1% writable") % settings.nixStore);
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#endif
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}
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