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core: move bpf devices implementation to bpf-devices.[ch] and rename

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The naming of the functions was a complete mess: the most specific functions
which don't know anything about cgroups had "cgroup_" prefix, while more
general functions which took a node path and a cgroup for reporting had no
prefix. Let's use "bpf_devices_" for the latter group, and "bpf_prog_*" for the
rest.

The main goal of this move is to split the implementation from the calling code
and add unit tests in a later patch.
This commit is contained in:
Zbigniew Jędrzejewski-Szmek
2019-11-10 23:22:15 +01:00
parent 084870f9c0
commit 124e05b3b6
3 changed files with 174 additions and 170 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/core/bpf-devices.c
+160 -5
View File
@@ -1,8 +1,16 @@
/* SPDX-License-Identifier: LGPL-2.1+ */
#include <fnmatch.h>
#include <linux/bpf_insn.h>
#include "bpf-devices.h"
#include "bpf-program.h"
#include "fd-util.h"
#include "fileio.h"
#include "parse-util.h"
#include "stat-util.h"
#include "stdio-util.h"
#include "string-util.h"
#define PASS_JUMP_OFF 4096
@@ -29,7 +37,7 @@ static int bpf_access_type(const char *acc) {
return r;
}
int cgroup_bpf_whitelist_device(BPFProgram *prog, int type, int major, int minor, const char *acc) {
static int bpf_prog_whitelist_device(BPFProgram *prog, int type, int major, int minor, const char *acc) {
int r, access;
assert(prog);
@@ -56,7 +64,7 @@ int cgroup_bpf_whitelist_device(BPFProgram *prog, int type, int major, int minor
return r;
}
int cgroup_bpf_whitelist_major(BPFProgram *prog, int type, int major, const char *acc) {
static int bpf_prog_whitelist_major(BPFProgram *prog, int type, int major, const char *acc) {
int r, access;
assert(prog);
@@ -82,7 +90,7 @@ int cgroup_bpf_whitelist_major(BPFProgram *prog, int type, int major, const char
return r;
}
int cgroup_bpf_whitelist_class(BPFProgram *prog, int type, const char *acc) {
static int bpf_prog_whitelist_class(BPFProgram *prog, int type, const char *acc) {
int r, access;
assert(prog);
@@ -107,7 +115,7 @@ int cgroup_bpf_whitelist_class(BPFProgram *prog, int type, const char *acc) {
return r;
}
int cgroup_init_device_bpf(BPFProgram **ret, CGroupDevicePolicy policy, bool whitelist) {
int bpf_devices_cgroup_init(BPFProgram **ret, CGroupDevicePolicy policy, bool whitelist) {
const struct bpf_insn pre_insn[] = {
/* load device type to r2 */
BPF_LDX_MEM(BPF_H, BPF_REG_2, BPF_REG_1,
@@ -150,7 +158,7 @@ int cgroup_init_device_bpf(BPFProgram **ret, CGroupDevicePolicy policy, bool whi
return 0;
}
int cgroup_apply_device_bpf(Unit *u, BPFProgram *prog, CGroupDevicePolicy policy, bool whitelist) {
int bpf_devices_apply_policy(Unit *u, BPFProgram *prog, CGroupDevicePolicy policy, bool whitelist) {
_cleanup_free_ char *path = NULL;
int r;
@@ -262,3 +270,150 @@ int bpf_devices_supported(void) {
return supported = 1;
}
static int whitelist_device_pattern(BPFProgram *prog, const char *path, char type, const unsigned *maj, const unsigned *min, const char *acc) {
assert(IN_SET(type, 'b', 'c'));
if (cg_all_unified() > 0) {
if (!prog)
return 0;
const int bpf_type = type == 'c' ? BPF_DEVCG_DEV_CHAR : BPF_DEVCG_DEV_BLOCK;
if (maj && min)
return bpf_prog_whitelist_device(prog, bpf_type, *maj, *min, acc);
else if (maj)
return bpf_prog_whitelist_major(prog, bpf_type, *maj, acc);
else
return bpf_prog_whitelist_class(prog, bpf_type, acc);
} else {
char buf[2+DECIMAL_STR_MAX(unsigned)*2+2+4];
int r;
if (maj && min)
xsprintf(buf, "%c %u:%u %s", type, *maj, *min, acc);
else if (maj)
xsprintf(buf, "%c %u:* %s", type, *maj, acc);
else
xsprintf(buf, "%c *:* %s", type, acc);
/* Changing the devices list of a populated cgroup might result in EINVAL, hence ignore
* EINVAL here. */
r = cg_set_attribute("devices", path, "devices.allow", buf);
if (r < 0)
log_full_errno(IN_SET(r, -ENOENT, -EROFS, -EINVAL, -EACCES, -EPERM) ? LOG_DEBUG : LOG_WARNING,
r, "Failed to set devices.allow on %s: %m", path);
return r;
}
}
int bpf_devices_whitelist_device(BPFProgram *prog, const char *path, const char *node, const char *acc) {
mode_t mode;
dev_t rdev;
int r;
assert(path);
assert(acc);
assert(strlen(acc) <= 3);
/* Some special handling for /dev/block/%u:%u, /dev/char/%u:%u, /run/systemd/inaccessible/chr and
* /run/systemd/inaccessible/blk paths. Instead of stat()ing these we parse out the major/minor directly. This
* means clients can use these path without the device node actually around */
r = device_path_parse_major_minor(node, &mode, &rdev);
if (r < 0) {
if (r != -ENODEV)
return log_warning_errno(r, "Couldn't parse major/minor from device path '%s': %m", node);
struct stat st;
if (stat(node, &st) < 0)
return log_warning_errno(errno, "Couldn't stat device %s: %m", node);
if (!S_ISCHR(st.st_mode) && !S_ISBLK(st.st_mode))
return log_warning_errno(SYNTHETIC_ERRNO(ENODEV), "%s is not a device.", node);
mode = st.st_mode;
rdev = (dev_t) st.st_rdev;
}
unsigned maj = major(rdev), min = minor(rdev);
return whitelist_device_pattern(prog, path, S_ISCHR(mode) ? 'c' : 'b', &maj, &min, acc);
}
int bpf_devices_whitelist_major(BPFProgram *prog, const char *path, const char *name, char type, const char *acc) {
unsigned maj;
int r;
assert(path);
assert(acc);
assert(IN_SET(type, 'b', 'c'));
if (streq(name, "*"))
/* If the name is a wildcard, then apply this list to all devices of this type */
return whitelist_device_pattern(prog, path, type, NULL, NULL, acc);
if (safe_atou(name, &maj) >= 0 && DEVICE_MAJOR_VALID(maj))
/* The name is numeric and suitable as major. In that case, let's take its major, and create
* the entry directly. */
return whitelist_device_pattern(prog, path, type, &maj, NULL, acc);
_cleanup_fclose_ FILE *f = NULL;
bool good = false;
f = fopen("/proc/devices", "re");
if (!f)
return log_warning_errno(errno, "Cannot open /proc/devices to resolve %s: %m", name);
for (;;) {
_cleanup_free_ char *line = NULL;
char *w, *p;
r = read_line(f, LONG_LINE_MAX, &line);
if (r < 0)
return log_warning_errno(r, "Failed to read /proc/devices: %m");
if (r == 0)
break;
if (type == 'c' && streq(line, "Character devices:")) {
good = true;
continue;
}
if (type == 'b' && streq(line, "Block devices:")) {
good = true;
continue;
}
if (isempty(line)) {
good = false;
continue;
}
if (!good)
continue;
p = strstrip(line);
w = strpbrk(p, WHITESPACE);
if (!w)
continue;
*w = 0;
r = safe_atou(p, &maj);
if (r < 0)
continue;
if (maj <= 0)
continue;
w++;
w += strspn(w, WHITESPACE);
if (fnmatch(name, w, 0) != 0)
continue;
(void) whitelist_device_pattern(prog, path, type, &maj, NULL, acc);
}
return 0;
}
src/core/bpf-devices.h
+5 -7
View File
@@ -7,11 +7,9 @@
struct BPFProgram;
int bpf_devices_cgroup_init(BPFProgram **ret, CGroupDevicePolicy policy, bool whitelist);
int bpf_devices_apply_policy(Unit *u, BPFProgram *prog, CGroupDevicePolicy policy, bool whitelist);
int bpf_devices_supported(void);
int cgroup_bpf_whitelist_device(BPFProgram *prog, int type, int major, int minor, const char *acc);
int cgroup_bpf_whitelist_major(BPFProgram *prog, int type, int major, const char *acc);
int cgroup_bpf_whitelist_class(BPFProgram *prog, int type, const char *acc);
int cgroup_init_device_bpf(BPFProgram **ret, CGroupDevicePolicy policy, bool whitelist);
int cgroup_apply_device_bpf(Unit *u, BPFProgram *prog, CGroupDevicePolicy policy, bool whitelist);
int bpf_devices_whitelist_device(BPFProgram *prog, const char *path, const char *node, const char *acc);
int bpf_devices_whitelist_major(BPFProgram *prog, const char *path, const char *name, char type, const char *acc);
src/core/cgroup.c
+9 -158
View File
@@ -1,7 +1,6 @@
/* SPDX-License-Identifier: LGPL-2.1+ */
#include <fcntl.h>
#include <fnmatch.h>
#include "sd-messages.h"
@@ -667,153 +666,6 @@ static int lookup_block_device(const char *p, dev_t *ret) {
return 0;
}
static int whitelist_device_pattern(BPFProgram *prog, const char *path, char type, const unsigned *maj, const unsigned *min, const char *acc) {
assert(IN_SET(type, 'b', 'c'));
if (cg_all_unified() > 0) {
if (!prog)
return 0;
const int bpf_type = type == 'c' ? BPF_DEVCG_DEV_CHAR : BPF_DEVCG_DEV_BLOCK;
if (maj && min)
return cgroup_bpf_whitelist_device(prog, bpf_type, *maj, *min, acc);
else if (maj)
return cgroup_bpf_whitelist_major(prog, bpf_type, *maj, acc);
else
return cgroup_bpf_whitelist_class(prog, bpf_type, acc);
} else {
char buf[2+DECIMAL_STR_MAX(unsigned)*2+2+4];
int r;
if (maj && min)
xsprintf(buf, "%c %u:%u %s", type, *maj, *min, acc);
else if (maj)
xsprintf(buf, "%c %u:* %s", type, *maj, acc);
else
xsprintf(buf, "%c *:* %s", type, acc);
/* Changing the devices list of a populated cgroup might result in EINVAL, hence ignore
* EINVAL here. */
r = cg_set_attribute("devices", path, "devices.allow", buf);
if (r < 0)
log_full_errno(IN_SET(r, -ENOENT, -EROFS, -EINVAL, -EACCES, -EPERM) ? LOG_DEBUG : LOG_WARNING,
r, "Failed to set devices.allow on %s: %m", path);
return r;
}
}
static int whitelist_device(BPFProgram *prog, const char *path, const char *node, const char *acc) {
mode_t mode;
dev_t rdev;
int r;
assert(path);
assert(acc);
assert(strlen(acc) <= 3);
/* Some special handling for /dev/block/%u:%u, /dev/char/%u:%u, /run/systemd/inaccessible/chr and
* /run/systemd/inaccessible/blk paths. Instead of stat()ing these we parse out the major/minor directly. This
* means clients can use these path without the device node actually around */
r = device_path_parse_major_minor(node, &mode, &rdev);
if (r < 0) {
if (r != -ENODEV)
return log_warning_errno(r, "Couldn't parse major/minor from device path '%s': %m", node);
struct stat st;
if (stat(node, &st) < 0)
return log_warning_errno(errno, "Couldn't stat device %s: %m", node);
if (!S_ISCHR(st.st_mode) && !S_ISBLK(st.st_mode))
return log_warning_errno(SYNTHETIC_ERRNO(ENODEV), "%s is not a device.", node);
mode = st.st_mode;
rdev = (dev_t) st.st_rdev;
}
unsigned maj = major(rdev), min = minor(rdev);
return whitelist_device_pattern(prog, path, S_ISCHR(mode) ? 'c' : 'b', &maj, &min, acc);
}
static int whitelist_major(BPFProgram *prog, const char *path, const char *name, char type, const char *acc) {
unsigned maj;
int r;
assert(path);
assert(acc);
assert(IN_SET(type, 'b', 'c'));
if (streq(name, "*"))
/* If the name is a wildcard, then apply this list to all devices of this type */
return whitelist_device_pattern(prog, path, type, NULL, NULL, acc);
if (safe_atou(name, &maj) >= 0 && DEVICE_MAJOR_VALID(maj))
/* The name is numeric and suitable as major. In that case, let's take its major, and create
* the entry directly. */
return whitelist_device_pattern(prog, path, type, &maj, NULL, acc);
_cleanup_fclose_ FILE *f = NULL;
bool good = false;
f = fopen("/proc/devices", "re");
if (!f)
return log_warning_errno(errno, "Cannot open /proc/devices to resolve %s: %m", name);
for (;;) {
_cleanup_free_ char *line = NULL;
char *w, *p;
r = read_line(f, LONG_LINE_MAX, &line);
if (r < 0)
return log_warning_errno(r, "Failed to read /proc/devices: %m");
if (r == 0)
break;
if (type == 'c' && streq(line, "Character devices:")) {
good = true;
continue;
}
if (type == 'b' && streq(line, "Block devices:")) {
good = true;
continue;
}
if (isempty(line)) {
good = false;
continue;
}
if (!good)
continue;
p = strstrip(line);
w = strpbrk(p, WHITESPACE);
if (!w)
continue;
*w = 0;
r = safe_atou(p, &maj);
if (r < 0)
continue;
if (maj <= 0)
continue;
w++;
w += strspn(w, WHITESPACE);
if (fnmatch(name, w, 0) != 0)
continue;
(void) whitelist_device_pattern(prog, path, type, &maj, NULL, acc);
}
return 0;
}
static bool cgroup_context_has_cpu_weight(CGroupContext *c) {
return c->cpu_weight != CGROUP_WEIGHT_INVALID ||
c->startup_cpu_weight != CGROUP_WEIGHT_INVALID;
@@ -1385,7 +1237,7 @@ static void cgroup_context_apply(
CGroupDeviceAllow *a;
if (cg_all_unified() > 0) {
r = cgroup_init_device_bpf(&prog, c->device_policy, c->device_allow);
r = bpf_devices_cgroup_init(&prog, c->device_policy, c->device_allow);
if (r < 0)
log_unit_warning_errno(u, r, "Failed to initialize device control bpf program: %m");
} else {
@@ -1415,13 +1267,12 @@ static void cgroup_context_apply(
"/run/systemd/inaccessible/chr\0" "rwm\0"
"/run/systemd/inaccessible/blk\0" "rwm\0";
const char *x, *y;
NULSTR_FOREACH_PAIR(x, y, auto_devices)
(void) whitelist_device(prog, path, x, y);
const char *node, *acc;
NULSTR_FOREACH_PAIR(node, acc, auto_devices)
(void) bpf_devices_whitelist_device(prog, path, node, acc);
/* PTS (/dev/pts) devices may not be duplicated, but accessed */
(void) whitelist_major(prog, path, "pts", 'c', "rw");
(void) bpf_devices_whitelist_major(prog, path, "pts", 'c', "rw");
}
LIST_FOREACH(device_allow, a, c->device_allow) {
@@ -1441,16 +1292,16 @@ static void cgroup_context_apply(
acc[k++] = 0;
if (path_startswith(a->path, "/dev/"))
(void) whitelist_device(prog, path, a->path, acc);
(void) bpf_devices_whitelist_device(prog, path, a->path, acc);
else if ((val = startswith(a->path, "block-")))
(void) whitelist_major(prog, path, val, 'b', acc);
(void) bpf_devices_whitelist_major(prog, path, val, 'b', acc);
else if ((val = startswith(a->path, "char-")))
(void) whitelist_major(prog, path, val, 'c', acc);
(void) bpf_devices_whitelist_major(prog, path, val, 'c', acc);
else
log_unit_debug(u, "Ignoring device '%s' while writing cgroup attribute.", a->path);
}
r = cgroup_apply_device_bpf(u, prog, c->device_policy, c->device_allow);
r = bpf_devices_apply_policy(u, prog, c->device_policy, c->device_allow);
if (r < 0) {
static bool warned = false;