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core/namespace: introduce new mount mode READWRITE_IMPLICIT

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ProtectSystem=strict or ProtectKernelTunable=yes create implicit
read-write mounts, but they are not overridable by TemporaryFileSystem=.
This makes such implicit read-write mounts use the new mount mode.
So, they can be override by TemproraryFileSystem= now.
A typical usecase is that ProtectSystem=strict and ProtectHome=tmpfs.

Fixes #11276.
This commit is contained in:
Yu Watanabe 2018-12-28 16:11:52 +09:00
parent fbaefc3ff9
commit 1e05071d27
1 changed files with 32 additions and 30 deletions
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62
src/core/namespace.c
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@ -49,6 +49,7 @@ typedef enum MountMode {
READONLY,
READWRITE,
TMPFS,
READWRITE_IMPLICIT, /* Should have the lowest priority. */
} MountMode;
typedef struct MountEntry {
@ -77,26 +78,26 @@ static const MountEntry apivfs_table[] = {
/* ProtectKernelTunables= option and the related filesystem APIs */
static const MountEntry protect_kernel_tunables_table[] = {
{ "/proc/acpi", READONLY, true },
{ "/proc/apm", READONLY, true }, /* Obsolete API, there's no point in permitting access to this, ever */
{ "/proc/asound", READONLY, true },
{ "/proc/bus", READONLY, true },
{ "/proc/fs", READONLY, true },
{ "/proc/irq", READONLY, true },
{ "/proc/kallsyms", INACCESSIBLE, true },
{ "/proc/kcore", INACCESSIBLE, true },
{ "/proc/latency_stats", READONLY, true },
{ "/proc/mtrr", READONLY, true },
{ "/proc/scsi", READONLY, true },
{ "/proc/sys", READONLY, false },
{ "/proc/sysrq-trigger", READONLY, true },
{ "/proc/timer_stats", READONLY, true },
{ "/sys", READONLY, false },
{ "/sys/fs/bpf", READONLY, true },
{ "/sys/fs/cgroup", READWRITE, false }, /* READONLY is set by ProtectControlGroups= option */
{ "/sys/fs/selinux", READWRITE, true },
{ "/sys/kernel/debug", READONLY, true },
{ "/sys/kernel/tracing", READONLY, true },
{ "/proc/acpi", READONLY, true },
{ "/proc/apm", READONLY, true }, /* Obsolete API, there's no point in permitting access to this, ever */
{ "/proc/asound", READONLY, true },
{ "/proc/bus", READONLY, true },
{ "/proc/fs", READONLY, true },
{ "/proc/irq", READONLY, true },
{ "/proc/kallsyms", INACCESSIBLE, true },
{ "/proc/kcore", INACCESSIBLE, true },
{ "/proc/latency_stats", READONLY, true },
{ "/proc/mtrr", READONLY, true },
{ "/proc/scsi", READONLY, true },
{ "/proc/sys", READONLY, false },
{ "/proc/sysrq-trigger", READONLY, true },
{ "/proc/timer_stats", READONLY, true },
{ "/sys", READONLY, false },
{ "/sys/fs/bpf", READONLY, true },
{ "/sys/fs/cgroup", READWRITE_IMPLICIT, false }, /* READONLY is set by ProtectControlGroups= option */
{ "/sys/fs/selinux", READWRITE_IMPLICIT, true },
{ "/sys/kernel/debug", READONLY, true },
{ "/sys/kernel/tracing", READONLY, true },
};
/* ProtectKernelModules= option */
@ -171,13 +172,13 @@ static const MountEntry protect_system_full_table[] = {
* shall manage those, orthogonally).
*/
static const MountEntry protect_system_strict_table[] = {
{ "/", READONLY, false },
{ "/proc", READWRITE, false }, /* ProtectKernelTunables= */
{ "/sys", READWRITE, false }, /* ProtectKernelTunables= */
{ "/dev", READWRITE, false }, /* PrivateDevices= */
{ "/home", READWRITE, true }, /* ProtectHome= */
{ "/run/user", READWRITE, true }, /* ProtectHome= */
{ "/root", READWRITE, true }, /* ProtectHome= */
{ "/", READONLY, false },
{ "/proc", READWRITE_IMPLICIT, false }, /* ProtectKernelTunables= */
{ "/sys", READWRITE_IMPLICIT, false }, /* ProtectKernelTunables= */
{ "/dev", READWRITE_IMPLICIT, false }, /* PrivateDevices= */
{ "/home", READWRITE_IMPLICIT, true }, /* ProtectHome= */
{ "/run/user", READWRITE_IMPLICIT, true }, /* ProtectHome= */
{ "/root", READWRITE_IMPLICIT, true }, /* ProtectHome= */
};
static const char *mount_entry_path(const MountEntry *p) {
@ -220,7 +221,7 @@ static int append_access_mounts(MountEntry **p, char **strv, MountMode mode, boo
assert(p);
/* Adds a list of user-supplied READWRITE/READONLY/INACCESSIBLE entries */
/* Adds a list of user-supplied READWRITE/READWRITE_IMPLICIT/READONLY/INACCESSIBLE entries */
STRV_FOREACH(i, strv) {
bool ignore = false, needs_prefix = false;
@ -500,8 +501,8 @@ static void drop_nop(MountEntry *m, size_t *n) {
for (f = m, t = m; f < m + *n; f++) {
/* Only suppress such subtrees for READONLY and READWRITE entries */
if (IN_SET(f->mode, READONLY, READWRITE)) {
/* Only suppress such subtrees for READONLY, READWRITE and READWRITE_IMPLICIT entries */
if (IN_SET(f->mode, READONLY, READWRITE, READWRITE_IMPLICIT)) {
MountEntry *p;
bool found = false;
@ -908,6 +909,7 @@ static int apply_mount(
case READONLY:
case READWRITE:
case READWRITE_IMPLICIT:
r = path_is_mount_point(mount_entry_path(m), root_directory, 0);
if (r == -ENOENT && m->ignore)
return 0;