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tree-wide: add size limits for tmpfs mounts

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Limit size of various tmpfs mounts to 10% of RAM, except volatile root and /var
to 25%. Another exception is made for /dev (also /devs for PrivateDevices) and
/sys/fs/cgroup since no (or very few) regular files are expected to be used.

In addition, since directories, symbolic links, device specials and xattrs are
not counted towards the size= limit, number of inodes is also limited
correspondingly: 4MB size translates to 1k of inodes (assuming 4k each), 10% of
RAM (using 16GB of RAM as baseline) translates to 400k and 25% to 1M inodes.

Because nr_inodes option can't use ratios like size option, there's an
unfortunate side effect that with small memory systems the limit may be on the
too large side. Also, on an extremely small device with only 256MB of RAM, 10%
of RAM for /run may not be enough for re-exec of PID1 because 16MB of free
space is required.
This commit is contained in:
Topi Miettinen
2020-05-13 00:37:18 +02:00
committed by Lennart Poettering
parent 7cc8fb3ef0
commit 7d85383edb
8 changed files with 63 additions and 45 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/nspawn/nspawn-cgroup.c
+2 -2
View File
@@ -319,7 +319,7 @@ static int mount_legacy_cgns_supported(
* uid/gid as seen from e.g. /proc/1/mountinfo. So we simply
* pass uid 0 and not uid_shift to tmpfs_patch_options().
*/
r = tmpfs_patch_options("mode=755", 0, selinux_apifs_context, &options);
r = tmpfs_patch_options("mode=755" TMPFS_LIMITS_SYS_FS_CGROUP, 0, selinux_apifs_context, &options);
if (r < 0)
return log_oom();
@@ -421,7 +421,7 @@ static int mount_legacy_cgns_unsupported(
if (r == 0) {
_cleanup_free_ char *options = NULL;
r = tmpfs_patch_options("mode=755", uid_shift == 0 ? UID_INVALID : uid_shift, selinux_apifs_context, &options);
r = tmpfs_patch_options("mode=755" TMPFS_LIMITS_SYS_FS_CGROUP, uid_shift == 0 ? UID_INVALID : uid_shift, selinux_apifs_context, &options);
if (r < 0)
return log_oom();
src/nspawn/nspawn-mount.c
+12 -12
View File
@@ -602,25 +602,25 @@ int mount_all(const char *dest,
MOUNT_IN_USERNS|MOUNT_MKDIR },
/* Then we list outer child mounts (i.e. mounts applied *before* entering user namespacing) */
{ "tmpfs", "/tmp", "tmpfs", "mode=1777", MS_NOSUID|MS_NODEV|MS_STRICTATIME,
{ "tmpfs", "/tmp", "tmpfs", "mode=1777" TMPFS_LIMITS_TMP, MS_NOSUID|MS_NODEV|MS_STRICTATIME,
MOUNT_FATAL|MOUNT_APPLY_TMPFS_TMP|MOUNT_MKDIR },
{ "tmpfs", "/sys", "tmpfs", "mode=555", MS_NOSUID|MS_NOEXEC|MS_NODEV,
{ "tmpfs", "/sys", "tmpfs", "mode=555" TMPFS_LIMITS_SYS, MS_NOSUID|MS_NOEXEC|MS_NODEV,
MOUNT_FATAL|MOUNT_APPLY_APIVFS_NETNS|MOUNT_MKDIR },
{ "sysfs", "/sys", "sysfs", NULL, MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV,
{ "sysfs", "/sys", "sysfs", NULL, MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV,
MOUNT_FATAL|MOUNT_APPLY_APIVFS_RO|MOUNT_MKDIR }, /* skipped if above was mounted */
{ "sysfs", "/sys", "sysfs", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
{ "sysfs", "/sys", "sysfs", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV,
MOUNT_FATAL|MOUNT_MKDIR }, /* skipped if above was mounted */
{ "tmpfs", "/dev", "tmpfs", "mode=755", MS_NOSUID|MS_STRICTATIME,
{ "tmpfs", "/dev", "tmpfs", "mode=755" TMPFS_LIMITS_DEV, MS_NOSUID|MS_STRICTATIME,
MOUNT_FATAL|MOUNT_MKDIR },
{ "tmpfs", "/dev/shm", "tmpfs", "mode=1777", MS_NOSUID|MS_NODEV|MS_STRICTATIME,
{ "tmpfs", "/dev/shm", "tmpfs", "mode=1777" TMPFS_LIMITS_DEV_SHM, MS_NOSUID|MS_NODEV|MS_STRICTATIME,
MOUNT_FATAL|MOUNT_MKDIR },
{ "tmpfs", "/run", "tmpfs", "mode=755", MS_NOSUID|MS_NODEV|MS_STRICTATIME,
{ "tmpfs", "/run", "tmpfs", "mode=755" TMPFS_LIMITS_RUN, MS_NOSUID|MS_NODEV|MS_STRICTATIME,
MOUNT_FATAL|MOUNT_MKDIR },
#if HAVE_SELINUX
{ "/sys/fs/selinux", "/sys/fs/selinux", NULL, NULL, MS_BIND,
{ "/sys/fs/selinux", "/sys/fs/selinux", NULL, NULL, MS_BIND,
0 }, /* Bind mount first */
{ NULL, "/sys/fs/selinux", NULL, NULL, MS_BIND|MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_REMOUNT,
{ NULL, "/sys/fs/selinux", NULL, NULL, MS_BIND|MS_RDONLY|MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_REMOUNT,
0 }, /* Then, make it r/o */
#endif
};
@@ -1023,7 +1023,7 @@ static int setup_volatile_state(const char *directory, uid_t uid_shift, const ch
if (r < 0 && errno != EEXIST)
return log_error_errno(errno, "Failed to create %s: %m", directory);
options = "mode=755";
options = "mode=755" TMPFS_LIMITS_VOLATILE_STATE;
r = tmpfs_patch_options(options, uid_shift == 0 ? UID_INVALID : uid_shift, selinux_apifs_context, &buf);
if (r < 0)
return log_oom();
@@ -1068,7 +1068,7 @@ static int setup_volatile_yes(const char *directory, uid_t uid_shift, const char
if (!mkdtemp(template))
return log_error_errno(errno, "Failed to create temporary directory: %m");
options = "mode=755";
options = "mode=755" TMPFS_LIMITS_ROOTFS;
r = tmpfs_patch_options(options, uid_shift == 0 ? UID_INVALID : uid_shift, selinux_apifs_context, &buf);
if (r < 0)
goto fail;
@@ -1135,7 +1135,7 @@ static int setup_volatile_overlay(const char *directory, uid_t uid_shift, const
if (!mkdtemp(template))
return log_error_errno(errno, "Failed to create temporary directory: %m");
options = "mode=755";
options = "mode=755" TMPFS_LIMITS_ROOTFS;
r = tmpfs_patch_options(options, uid_shift == 0 ? UID_INVALID : uid_shift, selinux_apifs_context, &buf);
if (r < 0)
goto finish;