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From 08c48bbe717a0be0f8c41a4652473d8483e0fbde Mon Sep 17 00:00:00 2001
From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Tue, 23 May 2023 17:49:16 +0900
Subject: [PATCH] core/unit: update bidirectional dependency simultaneously
Previously, if unit_add_dependency_hashmap() failed, then a
one-directional unit dependency reference might be created, and
triggeres use-after-free. See issue #27742 for more details.
This makes unit dependency always bidirectional, and cleanly revert
partial update on failure.
Fixes #27742.
(cherry picked from commit 831108245eb757f41fe0ebbccf1b42c9dd0ce297)
Resolves: #2213521
---
src/core/unit.c | 164 ++++++++++++++++++++++++++++++------------------
1 file changed, 103 insertions(+), 61 deletions(-)
diff --git a/src/core/unit.c b/src/core/unit.c
index 6acc63e091..438213a47a 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -990,46 +990,6 @@ static int unit_per_dependency_type_hashmap_update(
return 1;
}
-static int unit_add_dependency_hashmap(
- Hashmap **dependencies,
- UnitDependency d,
- Unit *other,
- UnitDependencyMask origin_mask,
- UnitDependencyMask destination_mask) {
-
- Hashmap *per_type;
- int r;
-
- assert(dependencies);
- assert(other);
- assert(origin_mask < _UNIT_DEPENDENCY_MASK_FULL);
- assert(destination_mask < _UNIT_DEPENDENCY_MASK_FULL);
- assert(origin_mask > 0 || destination_mask > 0);
-
- /* Ensure the top-level dependency hashmap exists that maps UnitDependency → Hashmap(Unit* →
- * UnitDependencyInfo) */
- r = hashmap_ensure_allocated(dependencies, NULL);
- if (r < 0)
- return r;
-
- /* Acquire the inner hashmap, that maps Unit* → UnitDependencyInfo, for the specified dependency
- * type, and if it's missing allocate it and insert it. */
- per_type = hashmap_get(*dependencies, UNIT_DEPENDENCY_TO_PTR(d));
- if (!per_type) {
- per_type = hashmap_new(NULL);
- if (!per_type)
- return -ENOMEM;
-
- r = hashmap_put(*dependencies, UNIT_DEPENDENCY_TO_PTR(d), per_type);
- if (r < 0) {
- hashmap_free(per_type);
- return r;
- }
- }
-
- return unit_per_dependency_type_hashmap_update(per_type, other, origin_mask, destination_mask);
-}
-
static void unit_merge_dependencies(Unit *u, Unit *other) {
Hashmap *deps;
void *dt; /* Actually of type UnitDependency, except that we don't bother casting it here,
@@ -3002,11 +2962,38 @@ bool unit_job_is_applicable(Unit *u, JobType j) {
}
}
-int unit_add_dependency(
+static Hashmap *unit_get_dependency_hashmap_per_type(Unit *u, UnitDependency d) {
+ Hashmap *deps;
+
+ assert(u);
+ assert(d >= 0 && d < _UNIT_DEPENDENCY_MAX);
+
+ deps = hashmap_get(u->dependencies, UNIT_DEPENDENCY_TO_PTR(d));
+ if (!deps) {
+ _cleanup_hashmap_free_ Hashmap *h = NULL;
+
+ h = hashmap_new(NULL);
+ if (!h)
+ return NULL;
+
+ if (hashmap_ensure_put(&u->dependencies, NULL, UNIT_DEPENDENCY_TO_PTR(d), h) < 0)
+ return NULL;
+
+ deps = TAKE_PTR(h);
+ }
+
+ return deps;
+}
+
+typedef enum NotifyDependencyFlags {
+ NOTIFY_DEPENDENCY_UPDATE_FROM = 1 << 0,
+ NOTIFY_DEPENDENCY_UPDATE_TO = 1 << 1,
+} NotifyDependencyFlags;
+
+static int unit_add_dependency_impl(
Unit *u,
UnitDependency d,
Unit *other,
- bool add_reference,
UnitDependencyMask mask) {
static const UnitDependency inverse_table[_UNIT_DEPENDENCY_MAX] = {
@@ -3042,12 +3029,78 @@ int unit_add_dependency(
[UNIT_IN_SLICE] = UNIT_SLICE_OF,
[UNIT_SLICE_OF] = UNIT_IN_SLICE,
};
+
+ Hashmap *u_deps, *other_deps;
+ UnitDependencyInfo u_info, u_info_old, other_info, other_info_old;
+ NotifyDependencyFlags flags = 0;
+ int r;
+
+ assert(u);
+ assert(other);
+ assert(d >= 0 && d < _UNIT_DEPENDENCY_MAX);
+ assert(inverse_table[d] >= 0 && inverse_table[d] < _UNIT_DEPENDENCY_MAX);
+ assert(mask > 0 && mask < _UNIT_DEPENDENCY_MASK_FULL);
+
+ /* Ensure the following two hashmaps for each unit exist:
+ * - the top-level dependency hashmap that maps UnitDependency → Hashmap(Unit* → UnitDependencyInfo),
+ * - the inner hashmap, that maps Unit* → UnitDependencyInfo, for the specified dependency type. */
+ u_deps = unit_get_dependency_hashmap_per_type(u, d);
+ if (!u_deps)
+ return -ENOMEM;
+
+ other_deps = unit_get_dependency_hashmap_per_type(other, inverse_table[d]);
+ if (!other_deps)
+ return -ENOMEM;
+
+ /* Save the original dependency info. */
+ u_info.data = u_info_old.data = hashmap_get(u_deps, other);
+ other_info.data = other_info_old.data = hashmap_get(other_deps, u);
+
+ /* Update dependency info. */
+ u_info.origin_mask |= mask;
+ other_info.destination_mask |= mask;
+
+ /* Save updated dependency info. */
+ if (u_info.data != u_info_old.data) {
+ r = hashmap_replace(u_deps, other, u_info.data);
+ if (r < 0)
+ return r;
+
+ flags = NOTIFY_DEPENDENCY_UPDATE_FROM;
+ }
+
+ if (other_info.data != other_info_old.data) {
+ r = hashmap_replace(other_deps, u, other_info.data);
+ if (r < 0) {
+ if (u_info.data != u_info_old.data) {
+ /* Restore the old dependency. */
+ if (u_info_old.data)
+ (void) hashmap_update(u_deps, other, u_info_old.data);
+ else
+ hashmap_remove(u_deps, other);
+ }
+ return r;
+ }
+
+ flags |= NOTIFY_DEPENDENCY_UPDATE_TO;
+ }
+
+ return flags;
+}
+
+int unit_add_dependency(
+ Unit *u,
+ UnitDependency d,
+ Unit *other,
+ bool add_reference,
+ UnitDependencyMask mask) {
+
UnitDependencyAtom a;
int r;
/* Helper to know whether sending a notification is necessary or not: if the dependency is already
* there, no need to notify! */
- bool notify, notify_other = false;
+ NotifyDependencyFlags notify_flags;
assert(u);
assert(d >= 0 && d < _UNIT_DEPENDENCY_MAX);
@@ -3103,35 +3156,24 @@ int unit_add_dependency(
return log_unit_error_errno(u, SYNTHETIC_ERRNO(EINVAL),
"Requested dependency SliceOf=%s refused (%s is not a cgroup unit).", other->id, other->id);
- r = unit_add_dependency_hashmap(&u->dependencies, d, other, mask, 0);
- if (r < 0)
- return r;
- notify = r > 0;
-
- assert(inverse_table[d] >= 0 && inverse_table[d] < _UNIT_DEPENDENCY_MAX);
- r = unit_add_dependency_hashmap(&other->dependencies, inverse_table[d], u, 0, mask);
+ r = unit_add_dependency_impl(u, d, other, mask);
if (r < 0)
return r;
- notify_other = r > 0;
+ notify_flags = r;
if (add_reference) {
- r = unit_add_dependency_hashmap(&u->dependencies, UNIT_REFERENCES, other, mask, 0);
- if (r < 0)
- return r;
- notify = notify || r > 0;
-
- r = unit_add_dependency_hashmap(&other->dependencies, UNIT_REFERENCED_BY, u, 0, mask);
+ r = unit_add_dependency_impl(u, UNIT_REFERENCES, other, mask);
if (r < 0)
return r;
- notify_other = notify_other || r > 0;
+ notify_flags |= r;
}
- if (notify)
+ if (FLAGS_SET(notify_flags, NOTIFY_DEPENDENCY_UPDATE_FROM))
unit_add_to_dbus_queue(u);
- if (notify_other)
+ if (FLAGS_SET(notify_flags, NOTIFY_DEPENDENCY_UPDATE_TO))
unit_add_to_dbus_queue(other);
- return notify || notify_other;
+ return notify_flags != 0;
}
int unit_add_two_dependencies(Unit *u, UnitDependency d, UnitDependency e, Unit *other, bool add_reference, UnitDependencyMask mask) {
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