Hi,
Following Manolo's review, here is the gnumach half of a v2 for the port-entry
limit. To be clear up front: this is public analysis, not a submission. As I
told Michael, I cannot sign FSF papers, so I am not asking anyone to merge it.
If a contributor who has signed wants to carry it, it is theirs, and I will
answer design questions.
What it does:
- ipc/ipc_space.h: replaces the single cap with is_cur_limit / is_max_limit,
defaulting to 65536 entries. Same shape as vm_map's size_cur_limit /
size_max_limit.
- ipc/ipc_entry.c: both growth paths (ipc_entry_alloc, ipc_entry_alloc_name)
return KERN_NO_SPACE once is_size reaches is_cur_limit. Free-entry reuse stays
uncapped, so only growth is bounded.
- kern/ipc_tt.c: a child task inherits its parent's limits, the way
task_create_kernel inherits the VM map's limits. This is the kernel half of
Manolo's inheritance point; the glibc half is separate.
- include/mach/task_info.h + kern/task.c: new TASK_PORT_ENTRY_LIMIT_INFO flavor
reads cur/max.
- include/mach/gnumach.defs + kern/task.c: task_set_port_entry_limit(host_port,
target_task, cur, max), mirroring vm_set_size_limit. Raising max needs the
privileged host port (IKOT_HOST_PRIV), otherwise KERN_NO_ACCESS; lowering is
unprivileged. cur > max is KERN_INVALID_ARGUMENT.
Diffstat: 7 files changed, 140 insertions. Applies clean at HEAD 0fa7374.
Not done yet, and not pretending otherwise: glibc (RLIMIT + init_rlimit + fork
inheritance), the resource utilities, and the ext2fs auto-raise. Those wait on
Manolo's answer to the interface question I asked (Hurd RLIMIT vs a Mach-native
flavor; I lean RLIMIT).
Two things I am unsure of and would rather flag than paper over: reading
target_task->itk_space in the setter without itk_lock (vm_set_size_limit does
the same with map, but task teardown is a different race), and whether flavor 4
is the right number for a new task_info flavor.
Sylvia
--- 8< --- gnumach port-entry limits, v2 (applies at 0fa7374) --- 8< ---
diff --git a/include/mach/gnumach.defs b/include/mach/gnumach.defs
index f5b2f7f..d5312a4 100644
--- a/include/mach/gnumach.defs
+++ b/include/mach/gnumach.defs
@@ -257,3 +257,27 @@ routine vm_get_size_limit(
map : vm_task_t;
out current_limit : vm_size_t;
out max_limit : vm_size_t);
+
+/*
+ * Set the current/maximum port-entry limits of TARGET_TASK's IPC
+ * space.
+ *
+ * HOST_PORT must be the privileged host control port to increase
+ * the max limit; the unprivileged host control port (as returned
+ * by mach_host_self()) is enough to decrease it.
+ *
+ * Returns:
+ * - KERN_SUCCESS
+ * - KERN_INVALID_TASK
+ * - KERN_INVALID_HOST
+ * - KERN_INVALID_ARGUMENT
+ * * when cur_limit > max_limit
+ * - KERN_NO_ACCESS
+ * * attempt to increase max_limit without providing the
+ * privileged host control port.
+ */
+routine task_set_port_entry_limit(
+ host_port : mach_port_t;
+ target_task : task_t;
+ cur_limit : long_natural_t;
+ max_limit : long_natural_t);
diff --git a/include/mach/task_info.h b/include/mach/task_info.h
index 0e048c5..fec4f3c 100644
--- a/include/mach/task_info.h
+++ b/include/mach/task_info.h
@@ -114,6 +114,18 @@ typedef struct task_thread_times_info
*task_thread_times_info_t;
#define TASK_THREAD_TIMES_INFO_COUNT \
(sizeof(task_thread_times_info_data_t) / sizeof(integer_t))
+#define TASK_PORT_ENTRY_LIMIT_INFO 4 /* port entry limits */
+
+struct task_port_entry_limit_info {
+ rpc_long_natural_t cur_limit; /* current limit on the number
+ of port entries */
+ rpc_long_natural_t max_limit; /* maximum limit a task may set
*/
+};
+typedef struct task_port_entry_limit_info
task_port_entry_limit_info_data_t;
+typedef struct task_port_entry_limit_info *task_port_entry_limit_info_t;
+#define TASK_PORT_ENTRY_LIMIT_INFO_COUNT \
+ (sizeof(task_port_entry_limit_info_data_t) / sizeof(integer_t))
+
/*
* Flavor definitions for task_ras_control
*/
diff --git a/ipc/ipc_entry.c b/ipc/ipc_entry.c
index f13c442..f19f775 100644
--- a/ipc/ipc_entry.c
+++ b/ipc/ipc_entry.c
@@ -82,6 +82,12 @@ ipc_entry_alloc(
if (kr == KERN_SUCCESS)
return kr;
+ /* Reusing a free entry above does not grow the space; only
+ growth is capped. A task leaking ports now fails its own
+ allocation instead of starving every other space. */
+ if (space->is_size >= space->is_cur_limit)
+ return KERN_NO_SPACE;
+
entry = ie_alloc();
if (entry == IE_NULL) {
return KERN_RESOURCE_SHORTAGE;
@@ -138,6 +144,9 @@ ipc_entry_alloc_name(
entry = *(ipc_entry_t *) slot;
if (slot == NULL || entry == IE_NULL) {
+ if (space->is_size >= space->is_cur_limit)
+ return KERN_NO_SPACE;
+
entry = ie_alloc();
if (entry == IE_NULL) {
return KERN_RESOURCE_SHORTAGE;
diff --git a/ipc/ipc_space.c b/ipc/ipc_space.c
index 77040d1..2d95665 100644
--- a/ipc/ipc_space.c
+++ b/ipc/ipc_space.c
@@ -118,6 +118,8 @@ ipc_space_create(
/* The zeroth entry is reserved. */
rdxtree_insert(&space->is_map, 0, &zero_entry);
space->is_size = 1;
+ space->is_cur_limit = IS_ENTRY_LIMIT_DEFAULT;
+ space->is_max_limit = IS_ENTRY_LIMIT_DEFAULT;
space->is_free_list = NULL;
space->is_free_list_size = 0;
@@ -125,6 +127,25 @@ ipc_space_create(
return KERN_SUCCESS;
}
+/*
+ * Routine: ipc_space_copy_limits
+ * Purpose:
+ * Copies the port-entry limits from SRC to DST.
+ * Conditions:
+ * DST is not yet shared; SRC is locked for reading here.
+ */
+
+void
+ipc_space_copy_limits(
+ struct ipc_space *dst,
+ struct ipc_space *src)
+{
+ is_read_lock(src);
+ dst->is_cur_limit = src->is_cur_limit;
+ dst->is_max_limit = src->is_max_limit;
+ is_read_unlock(src);
+}
+
/*
* Routine: ipc_space_create_special
* Purpose:
diff --git a/ipc/ipc_space.h b/ipc/ipc_space.h
index 9adbd3f..a1e6993 100644
--- a/ipc/ipc_space.h
+++ b/ipc/ipc_space.h
@@ -68,6 +68,9 @@ struct ipc_space {
boolean_t is_active; /* is the space alive? */
struct rdxtree is_map; /* a map of entries */
size_t is_size; /* number of entries */
+ size_t is_cur_limit; /* current limit on entries */
+ size_t is_max_limit; /* maximum limit an unprivileged
+ user is allowed to set */
struct rdxtree is_reverse_map; /* maps objects to entries */
ipc_entry_t is_free_list; /* a linked list of free entries */
size_t is_free_list_size; /* number of free entries */
@@ -75,6 +78,12 @@ struct ipc_space {
in the free list */
};
+/* Per-space port-name limits, mirroring vm_map's size_cur_limit and
+ size_max_limit. High enough that no legitimate client or server
+ hits it; low enough that a task leaking ports exhausts its own IPC
+ space instead of the machine's memory. */
+#define IS_ENTRY_LIMIT_DEFAULT (1u << 16)
+
#define IS_NULL ((ipc_space_t) 0)
@@ -122,6 +131,8 @@ MACRO_END
extern void ipc_space_reference(struct ipc_space *space);
extern void ipc_space_release(struct ipc_space *space);
+extern void ipc_space_copy_limits(struct ipc_space *dst,
+ struct ipc_space *src);
#define is_reference(is) ipc_space_reference_macro(is)
#define is_release(is) ipc_space_release_macro(is)
diff --git a/kern/ipc_tt.c b/kern/ipc_tt.c
index 7c9a0b8..39a807d 100644
--- a/kern/ipc_tt.c
+++ b/kern/ipc_tt.c
@@ -78,6 +78,11 @@ ipc_task_init(
if (kr != KERN_SUCCESS)
panic("ipc_task_init");
+ /* A child task inherits its parent's port-entry limits, the same
+ way task_create_kernel inherits the VM map's size limits. */
+ if (parent != TASK_NULL)
+ ipc_space_copy_limits(space, parent->itk_space);
+
kport = ipc_port_alloc_kernel();
if (kport == IP_NULL)
diff --git a/kern/task.c b/kern/task.c
index 07d2a02..4aa8176 100644
--- a/kern/task.c
+++ b/kern/task.c
@@ -925,6 +925,27 @@ kern_return_t task_info(
break;
}
+ case TASK_PORT_ENTRY_LIMIT_INFO:
+ {
+ task_port_entry_limit_info_t limit_info;
+ ipc_space_t space;
+
+ if (*task_info_count < TASK_PORT_ENTRY_LIMIT_INFO_COUNT) {
+ return KERN_INVALID_ARGUMENT;
+ }
+
+ limit_info = (task_port_entry_limit_info_t) task_info_out;
+ space = task->itk_space;
+
+ is_read_lock(space);
+ limit_info->cur_limit = space->is_cur_limit;
+ limit_info->max_limit = space->is_max_limit;
+ is_read_unlock(space);
+
+ *task_info_count = TASK_PORT_ENTRY_LIMIT_INFO_COUNT;
+ break;
+ }
+
default:
return KERN_INVALID_ARGUMENT;
}
@@ -1488,3 +1509,40 @@ task_max_priority(
task_unlock(task);
return ret;
}
+
+/*
+ * task_set_port_entry_limit:
+ *
+ * Set the current/max port-entry limits of TARGET_TASK's IPC space.
+ * Raising the max limit requires the privileged host port, exactly
+ * like vm_set_size_limit does for the address space.
+ */
+kern_return_t
+task_set_port_entry_limit(
+ const ipc_port_t host_port,
+ task_t target_task,
+ long_natural_t cur_limit,
+ long_natural_t max_limit)
+{
+ ipc_kobject_type_t ikot_host = extract_host_type(host_port);
+ ipc_space_t space;
+
+ if (ikot_host == IKOT_NONE)
+ return KERN_INVALID_HOST;
+ if (target_task == TASK_NULL)
+ return KERN_INVALID_TASK;
+ if (cur_limit > max_limit)
+ return KERN_INVALID_ARGUMENT;
+
+ space = target_task->itk_space;
+ is_write_lock(space);
+ if ((max_limit > space->is_max_limit) && (ikot_host != IKOT_HOST_PRIV))
{
+ is_write_unlock(space);
+ return KERN_NO_ACCESS;
+ }
+ space->is_cur_limit = cur_limit;
+ space->is_max_limit = max_limit;
+ is_write_unlock(space);
+
+ return KERN_SUCCESS;
+}
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