[PATCH net-next v8 0/2] binder: report txn errors via generic netlink

[PATCH net-next v8 0/2] binder: report txn errors via generic netlink

[Li Li]

From: Li Li <dualli@google.com>

It's a known issue that neither the frozen processes nor the system
administration process of the OS can correctly deal with failed binder
transactions. The reason is that there's no reliable way for the user
space administration process to fetch the binder errors from the kernel
binder driver.

Android is such an OS suffering from this issue. Since cgroup freezer
was used to freeze user applications to save battery, innocent frozen
apps have to be killed when they receive sync binder transactions or
when their async binder buffer is running out.

This patch introduces the Linux generic netlink messages into the binder
driver so that the Linux/Android system administration process can
listen to important events and take corresponding actions, like stopping
a broken app from attacking the OS by sending huge amount of spamming
binder transactiions.

The 1st version uses a global generic netlink for all binder contexts,
raising potential security concerns. There were a few other feedbacks
like request to kernel docs and test code. The thread can be found at
https://lore.kernel.org/lkml/20240812211844.4107494-1-dualli@chromium.org/

The 2nd version fixes those issues and has been tested on the latest
version of AOSP. See https://r.android.com/3305462 for how userspace is
going to use this feature and the test code. It can be found at
https://lore.kernel.org/lkml/20241011064427.1565287-1-dualli@chromium.org/

The 3rd version replaces the handcrafted netlink source code with the
netlink protocal specs in YAML. It also fixes the documentation issues.
https://lore.kernel.org/lkml/20241021182821.1259487-1-dualli@chromium.org/

The 4th version just containsi trivial fixes, making the subject of the
patch aligned with the subject of the cover letter.
https://lore.kernel.org/lkml/20241021191233.1334897-1-dualli@chromium.org/

The 5th version incorporates the suggested fixes to the kernel doc and
the init function. It also removes the unsupported uapi-header in YAML
that contains "/" for subdirectory.
https://lore.kernel.org/lkml/20241025075102.1785960-1-dualli@chromium.org/

The 6th version has some trivial kernel doc fixes, without modifying
any other source code.
https://lore.kernel.org/lkml/20241028101952.775731-1-dualli@chromium.org/

The 7th version breaks the binary struct netlink message into individual
attributes to better support automatic error checking. Thanks Jakub for
improving ynl-gen.
https://lore.kernel.org/all/20241031092504.840708-1-dualli@chromium.org/

The 8th version solves the multi-genl-family issue by demuxing the
messages based on a new context attribute. It also improves the YAML
spec to be consistent with netlink tradition. A Huge 'Thank You' to
Jakub who taught me a lot about the netlink protocol!

v1: add a global binder genl socket for all contexts
v2: change to per-context binder genl for security reason
    replace the new ioctl with a netlink command
    add corresponding doc Documentation/admin-guide/binder_genl.rst
    add user space test code in AOSP
v3: use YNL spec (./tools/net/ynl/ynl-regen.sh)
    fix documentation index
v4: change the subject of the patch and remove unsed #if 0
v5: improve the kernel doc and the init function
    remove unsupported uapi-header in YAML
v6: fix some trivial kernel doc issues
v7: break the binary struct binder_report into individual attributes
v8: use multiplex netlink message in a unified netlink family
    improve the YAML spec to be consistent with netlink tradition

Jakub Kicinski (1):
  tools: ynl-gen: allow uapi headers in sub-dirs

Li Li (1):
  binder: report txn errors via generic netlink

 Documentation/admin-guide/binder_genl.rst    |  96 +++++++
 Documentation/admin-guide/index.rst          |   1 +
 Documentation/netlink/specs/binder_genl.yaml | 108 +++++++
 drivers/android/Kconfig                      |   1 +
 drivers/android/Makefile                     |   2 +-
 drivers/android/binder.c                     | 287 ++++++++++++++++++-
 drivers/android/binder_genl.c                |  39 +++
 drivers/android/binder_genl.h                |  18 ++
 drivers/android/binder_internal.h            |  27 +-
 drivers/android/binder_trace.h               |  35 +++
 drivers/android/binderfs.c                   |   2 +
 include/uapi/linux/android/binder_genl.h     |  55 ++++
 tools/net/ynl/ynl-gen-c.py                   |   1 +
 13 files changed, 666 insertions(+), 6 deletions(-)
 create mode 100644 Documentation/admin-guide/binder_genl.rst
 create mode 100644 Documentation/netlink/specs/binder_genl.yaml
 create mode 100644 drivers/android/binder_genl.c
 create mode 100644 drivers/android/binder_genl.h
 create mode 100644 include/uapi/linux/android/binder_genl.h


base-commit: 31a1f8752f7df7e3d8122054fbef02a9a8bff38f
-- 
2.47.0.277.g8800431eea-goog

[PATCH net-next v8 1/2] tools: ynl-gen: allow uapi headers in sub-dirs

[Li Li]

From: Jakub Kicinski <kuba@kernel.org>

Binder places its headers under include/uapi/linux/android/
Make sure replace / with _ in the uAPI header guard, the c_upper()
is more strict and only converts - to _. This is likely a good
constraint to have, to enforce sane naming in enums etc.
But paths may include /.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Li Li <dualli@google.com>
---
 tools/net/ynl/ynl-gen-c.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/net/ynl/ynl-gen-c.py b/tools/net/ynl/ynl-gen-c.py
index c48b69071111..e548afa685fa 100755
--- a/tools/net/ynl/ynl-gen-c.py
+++ b/tools/net/ynl/ynl-gen-c.py
@@ -2416,6 +2416,7 @@ def uapi_enum_start(family, cw, obj, ckey='', enum_name='enum-name'):
 
 def render_uapi(family, cw):
     hdr_prot = f"_UAPI_LINUX_{c_upper(family.uapi_header_name)}_H"
+    hdr_prot = hdr_prot.replace('/', '_')
     cw.p('#ifndef ' + hdr_prot)
     cw.p('#define ' + hdr_prot)
     cw.nl()
-- 
2.47.0.277.g8800431eea-goog

[PATCH net-next v8 2/2] binder: report txn errors via generic netlink

[Li Li]

From: Li Li <dualli@google.com>

Frozen tasks can't process binder transactions, so sync binder
transactions will fail with BR_FROZEN_REPLY and async binder
transactions will be queued in the kernel async binder buffer.
As these queued async transactions accumulates over time, the async
buffer will eventually be running out, denying all new transactions
after that with BR_FAILED_REPLY.

In addition to the above cases, different kinds of binder error codes
might be returned to the sender. However, the core Linux, or Android,
system administration process never knows what's actually happening.

Introduce generic netlink messages into the binder driver so that the
Linux/Android system administration process can listen to important
events and take corresponding actions, like stopping a broken app from
attacking the OS by sending huge amount of spamming binder transactions.

The new binder genl sources and headers are automatically generated from
the corresponding binder_genl YAML spec. Don't modify them directly.

Signed-off-by: Li Li <dualli@google.com>
---
 Documentation/admin-guide/binder_genl.rst    |  96 +++++++
 Documentation/admin-guide/index.rst          |   1 +
 Documentation/netlink/specs/binder_genl.yaml | 108 +++++++
 drivers/android/Kconfig                      |   1 +
 drivers/android/Makefile                     |   2 +-
 drivers/android/binder.c                     | 287 ++++++++++++++++++-
 drivers/android/binder_genl.c                |  39 +++
 drivers/android/binder_genl.h                |  18 ++
 drivers/android/binder_internal.h            |  27 +-
 drivers/android/binder_trace.h               |  35 +++
 drivers/android/binderfs.c                   |   2 +
 include/uapi/linux/android/binder_genl.h     |  55 ++++
 12 files changed, 665 insertions(+), 6 deletions(-)
 create mode 100644 Documentation/admin-guide/binder_genl.rst
 create mode 100644 Documentation/netlink/specs/binder_genl.yaml
 create mode 100644 drivers/android/binder_genl.c
 create mode 100644 drivers/android/binder_genl.h
 create mode 100644 include/uapi/linux/android/binder_genl.h

diff --git a/Documentation/admin-guide/binder_genl.rst b/Documentation/admin-guide/binder_genl.rst
new file mode 100644
index 000000000000..b395d7a9849b
--- /dev/null
+++ b/Documentation/admin-guide/binder_genl.rst
@@ -0,0 +1,96 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===========================================================
+Generic Netlink for the Android Binder Driver (Binder Genl)
+===========================================================
+
+The Generic Netlink subsystem in the Linux kernel provides a generic way for
+the Linux kernel to communicate to the user space applications via binder
+driver. It is used to report various kinds of binder transactions to user
+space administration process. The driver allows multiple binder devices and
+their corresponding binder contexts. Each context has an independent Generic
+Netlink for security reason. To prevent untrusted user applications from
+accessing the netlink data, the kernel driver uses unicast mode instead of
+multicast.
+
+Basically, the user space code uses the "set" command to request what kind
+of binder transactions should be reported by the kernel binder driver. The
+driver then echoes the attributes in a reply message to acknowledge the
+request. The "set" command also registers the current user space process to
+receive the reports. When the user space process exits, the previous request
+will be reset to prevent any potential leaks.
+
+Currently the driver can report binder transactions that "failed" to reach
+the target process, or that are "delayed" due to the target process being
+frozen by cgroup freezer, or that are considered "spam" according to existing
+logic in binder_alloc.c.
+
+When the specified binder transactions happen, the driver uses the "report"
+command to send a generic netlink message to the registered process,
+containing the payload struct binder_report.
+
+More details about the flags, attributes and operations can be found at the
+the doc sections in Documentations/netlink/specs/binder_genl.yaml and the
+kernel-doc comments of the new source code in binder.{h|c}.
+
+Using Binder Genl
+-----------------
+
+The Binder Genl can be used in the same way as any other generic netlink
+drivers. Userspace application uses a raw netlink socket to send commands
+to and receive packets from the kernel driver.
+
+.. note::
+    If the userspace application that talks to the driver exits, the kernel
+    driver will automatically reset the configuration to the default and
+    stop sending more reports to prevent leaking memory.
+
+Usage example (user space pseudo code):
+
+::
+
+    // open netlink socket
+    int fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_GENERIC);
+
+    // bind netlink socket
+    bind(fd, struct socketaddr);
+
+    // get the family id of the binder genl
+    send(fd, CTRL_CMD_GETFAMILY, CTRL_ATTR_FAMILY_NAME,
+            BINDER_GENL_FAMILY_NAME);
+    void *data = recv(CTRL_CMD_NEWFAMILY);
+    __u16 id = nla(data)[CTRL_ATTR_FAMILY_ID];
+
+    // enable per-context binder report
+    send(fd, id, BINDER_GENL_CMD_SET, "binder", 0, BINDER_GENL_FLAG_FAILED |
+            BINDER_GENL_FLAG_DELAYED);
+
+    // confirm the per-context configuration
+    data = recv(fd, BINDER_GENL_CMD_REPLY);
+    char *context = nla(data)[BINDER_GENL_A_CMD_CONTEXT];
+    __u32 pid =  nla(data)[BINDER_GENL_A_CMD_PID];
+    __u32 flags = nla(data)[BINDER_GENL_A_CMD_FLAGS];
+
+    // set optional per-process report, overriding the per-context one
+    send(fd, id, BINDER_GENL_CMD_SET, "binder", getpid(),
+            BINDER_GENL_FLAG_SPAM | BINDER_REPORT_OVERRIDE);
+
+    // confirm the optional per-process configuration
+    data = recv(fd, BINDER_GENL_CMD_REPLY);
+    context = nla(data)[BINDER_GENL_A_CMD_CONTEXT];
+    pid =  nla(data)[BINDER_GENL_A_CMD_PID];
+    flags = nla(data)[BINDER_GENL_A_CMD_FLAGS];
+
+    // wait and read all binder reports
+    while (running) {
+            data = recv(fd, BINDER_GENL_CMD_REPORT);
+            auto *attr = nla(data)[BINDER_GENL_A_REPORT_XXX];
+
+            // process binder report
+            do_something(*attr);
+    }
+
+    // clean up
+    send(fd, id, BINDER_GENL_CMD_SET, 0, 0);
+    send(fd, id, BINDER_GENL_CMD_SET, getpid(), 0);
+    close(fd);
diff --git a/Documentation/admin-guide/index.rst b/Documentation/admin-guide/index.rst
index e85b1adf5908..b3b5cfadffe5 100644
--- a/Documentation/admin-guide/index.rst
+++ b/Documentation/admin-guide/index.rst
@@ -79,6 +79,7 @@ configure specific aspects of kernel behavior to your liking.
    aoe/index
    auxdisplay/index
    bcache
+   binder_genl
    binderfs
    binfmt-misc
    blockdev/index
diff --git a/Documentation/netlink/specs/binder_genl.yaml b/Documentation/netlink/specs/binder_genl.yaml
new file mode 100644
index 000000000000..3c6024b9a689
--- /dev/null
+++ b/Documentation/netlink/specs/binder_genl.yaml
@@ -0,0 +1,108 @@
+# SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)
+
+name: binder_genl
+protocol: genetlink
+uapi-header: linux/android/binder_genl.h
+doc: Netlink protocol to report binder transaction errors and warnings.
+
+definitions:
+  -
+    type: flags
+    name: flag
+    doc: Define what kind of binder transactions should be reported.
+    entries: [ failed, delayed, spam, override ]
+
+attribute-sets:
+  -
+    name: cmd
+    doc: The supported attributes of "set" and "reply" commands
+    attributes:
+      -
+        name: context
+        type: string
+        doc: The binder context to enable binder genl report.
+      -
+        name: pid
+        type: u32
+        doc: The binder proc to enable binder genl report.
+      -
+        name: flags
+        type: u32
+        enum: flag
+        doc: What kind of binder transactions should be reported.
+  -
+    name: report
+    doc: The supported attributes of "report" command
+    attributes:
+      -
+        name: context
+        type: string
+        doc: The binder context where the binder genl report happens.
+      -
+        name: err
+        type: u32
+        doc: Copy of binder_driver_return_protocol returned to the sender.
+      -
+        name: from_pid
+        type: u32
+        doc: Sender pid of the corresponding binder transaction.
+      -
+        name: from_tid
+        type: u32
+        doc: Sender tid of the corresponding binder transaction.
+      -
+        name: to_pid
+        type: u32
+        doc: Target pid of the corresponding binder transaction.
+      -
+        name: to_tid
+        type: u32
+        doc: Target tid of the corresponding binder transaction.
+      -
+        name: reply
+        type: u32
+        doc: 1 means the transaction is a reply, 0 otherwise.
+      -
+        name: flags
+        type: u32
+        doc: Copy of binder_transaction_data->flags.
+      -
+        name: code
+        type: u32
+        doc: Copy of binder_transaction_data->code.
+      -
+        name: data_size
+        type: u32
+        doc: Copy of binder_transaction_data->data_size.
+
+operations:
+  list:
+    -
+      name: set
+      doc: Set flags from user space.
+      attribute-set: cmd
+
+      do:
+        request: &params
+          attributes:
+            - context
+            - pid
+            - flags
+        reply: *params
+    -
+      name: report
+      doc: Send the requested reports to user space.
+      attribute-set: report
+
+      event:
+        attributes:
+          - context
+          - err
+          - from_pid
+          - from_tid
+          - to_pid
+          - to_tid
+          - reply
+          - flags
+          - code
+          - data_size
diff --git a/drivers/android/Kconfig b/drivers/android/Kconfig
index 07aa8ae0a058..e2fa620934e2 100644
--- a/drivers/android/Kconfig
+++ b/drivers/android/Kconfig
@@ -4,6 +4,7 @@ menu "Android"
 config ANDROID_BINDER_IPC
 	bool "Android Binder IPC Driver"
 	depends on MMU
+	depends on NET
 	default n
 	help
 	  Binder is used in Android for both communication between processes,
diff --git a/drivers/android/Makefile b/drivers/android/Makefile
index c9d3d0c99c25..d818447fbc4c 100644
--- a/drivers/android/Makefile
+++ b/drivers/android/Makefile
@@ -2,5 +2,5 @@
 ccflags-y += -I$(src)			# needed for trace events
 
 obj-$(CONFIG_ANDROID_BINDERFS)		+= binderfs.o
-obj-$(CONFIG_ANDROID_BINDER_IPC)	+= binder.o binder_alloc.o
+obj-$(CONFIG_ANDROID_BINDER_IPC)	+= binder.o binder_alloc.o binder_genl.o
 obj-$(CONFIG_ANDROID_BINDER_IPC_SELFTEST) += binder_alloc_selftest.o
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 978740537a1a..916803d56d86 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -72,6 +72,7 @@
 
 #include <linux/cacheflush.h>
 
+#include "binder_genl.h"
 #include "binder_internal.h"
 #include "binder_trace.h"
 
@@ -2984,6 +2985,153 @@ static void binder_set_txn_from_error(struct binder_transaction *t, int id,
 	binder_thread_dec_tmpref(from);
 }
 
+/**
+ * binder_find_proc() - set binder report flags
+ * @pid:	the target process
+ */
+static struct binder_proc *binder_find_proc(int pid)
+{
+	struct binder_proc *proc;
+
+	mutex_lock(&binder_procs_lock);
+	hlist_for_each_entry(proc, &binder_procs, proc_node) {
+		if (proc->pid == pid) {
+			mutex_unlock(&binder_procs_lock);
+			return proc;
+		}
+	}
+	mutex_unlock(&binder_procs_lock);
+
+	return NULL;
+}
+
+/**
+ * binder_genl_set_report() - set binder report flags
+ * @context:	the binder context to set the flags
+ * @pid:	the target process
+ * @flags:	the flags to set
+ *
+ * If pid is 0, the flags are applied to the whole binder context.
+ * Otherwise, the flags are applied to the specific process only.
+ */
+static int binder_genl_set_report(struct binder_context *context, u32 pid,
+				  u32 flags)
+{
+	struct binder_proc *proc;
+
+	if (flags != (flags & (BINDER_GENL_FLAG_OVERRIDE
+			| BINDER_GENL_FLAG_FAILED
+			| BINDER_GENL_FLAG_DELAYED
+			| BINDER_GENL_FLAG_SPAM))) {
+		pr_err("Invalid binder report flags: %u\n", flags);
+		return -EINVAL;
+	}
+
+	if (!pid) {
+		/* Set the global flags for the whole binder context */
+		context->report_flags = flags;
+	} else {
+		/* Set the per-process flags */
+		proc = binder_find_proc(pid);
+		if (!proc) {
+			pr_err("Invalid binder report pid %u\n", pid);
+			return -EINVAL;
+		}
+
+		proc->report_flags = flags;
+	}
+
+	return 0;
+}
+
+/**
+ * binder_genl_report_enabled() - check if binder genl reports are enabled
+ * @proc:	the binder_proc to check
+ * @mask:	the categories of binder genl reports
+ *
+ * Returns true if certain binder genl reports are enabled for this binder
+ * proc (when per-process overriding takes effect) or context.
+ */
+static bool binder_genl_report_enabled(struct binder_proc *proc, u32 mask)
+{
+	struct binder_context *context = proc->context;
+
+	if (!context->report_portid)
+		return false;
+
+	if (proc->report_flags & BINDER_GENL_FLAG_OVERRIDE)
+		return (proc->report_flags & mask) != 0;
+	else
+		return (context->report_flags & mask) != 0;
+}
+
+/**
+ * binder_genl_send_report() - send one binder genl report
+ * @context:	the binder context
+ * @err:	copy of binder_driver_return_protocol returned to the sender
+ * @pid:	sender process
+ * @tid:	sender thread
+ * @to_pid:	target process
+ * @to_tid:	target thread
+ * @reply:	whether the binder transaction is a reply
+ * @tr:		the binder transaction data
+ *
+ * Packs the report data into a "report" binder genl message and send it.
+ */
+static void binder_genl_send_report(struct binder_context *context, u32 err,
+				    u32 pid, u32 tid, u32 to_pid, u32 to_tid,
+				    u32 reply,
+				    struct binder_transaction_data *tr)
+{
+	int payload;
+	int ret;
+	struct sk_buff *skb;
+	void *hdr;
+
+	trace_binder_send_report(context->name, err, pid, tid, to_pid, to_tid,
+				 reply, tr);
+
+	payload = nla_total_size(strlen(context->name) + 1) +
+		  nla_total_size(sizeof(u32)) * (BINDER_GENL_A_REPORT_MAX - 1);
+	skb = genlmsg_new(payload + GENL_HDRLEN, GFP_KERNEL);
+	if (!skb) {
+		pr_err("Failed to alloc binder genl message\n");
+		return;
+	}
+
+	hdr = genlmsg_put(skb, 0, atomic_inc_return(&context->report_seq),
+			  &binder_genl_nl_family, 0, BINDER_GENL_CMD_REPORT);
+	if (!hdr)
+		goto free_skb;
+
+	if (nla_put_string(skb, BINDER_GENL_A_REPORT_CONTEXT, context->name) ||
+	    nla_put_u32(skb, BINDER_GENL_A_REPORT_ERR, err) ||
+	    nla_put_u32(skb, BINDER_GENL_A_REPORT_FROM_PID, pid) ||
+	    nla_put_u32(skb, BINDER_GENL_A_REPORT_FROM_TID, tid) ||
+	    nla_put_u32(skb, BINDER_GENL_A_REPORT_TO_PID, to_pid) ||
+	    nla_put_u32(skb, BINDER_GENL_A_REPORT_TO_TID, to_tid) ||
+	    nla_put_u32(skb, BINDER_GENL_A_REPORT_REPLY, reply) ||
+	    nla_put_u32(skb, BINDER_GENL_A_REPORT_FLAGS, tr->flags) ||
+	    nla_put_u32(skb, BINDER_GENL_A_REPORT_CODE, tr->code) ||
+	    nla_put_u32(skb, BINDER_GENL_A_REPORT_DATA_SIZE, tr->data_size))
+		goto cancel_skb;
+
+	genlmsg_end(skb, hdr);
+
+	ret = genlmsg_unicast(&init_net, skb, context->report_portid);
+	if (ret < 0)
+		pr_err("Failed to send binder genl message to %d: %d\n",
+		       context->report_portid, ret);
+	return;
+
+cancel_skb:
+	pr_err("Failed to add report attributes to binder genl message\n");
+	genlmsg_cancel(skb, hdr);
+free_skb:
+	pr_err("Free binder genl report message on error\n");
+	nlmsg_free(skb);
+}
+
 static void binder_transaction(struct binder_proc *proc,
 			       struct binder_thread *thread,
 			       struct binder_transaction_data *tr, int reply,
@@ -3678,10 +3826,18 @@ static void binder_transaction(struct binder_proc *proc,
 		return_error_line = __LINE__;
 		goto err_copy_data_failed;
 	}
-	if (t->buffer->oneway_spam_suspect)
+	if (t->buffer->oneway_spam_suspect) {
 		tcomplete->type = BINDER_WORK_TRANSACTION_ONEWAY_SPAM_SUSPECT;
-	else
+		if (binder_genl_report_enabled(proc, BINDER_GENL_FLAG_SPAM))
+			binder_genl_send_report(context,
+						BR_ONEWAY_SPAM_SUSPECT,
+						proc->pid, thread->pid,
+						target_proc ? target_proc->pid : 0,
+						target_thread ? target_thread->pid : 0,
+						reply, tr);
+	} else {
 		tcomplete->type = BINDER_WORK_TRANSACTION_COMPLETE;
+	}
 	t->work.type = BINDER_WORK_TRANSACTION;
 
 	if (reply) {
@@ -3731,8 +3887,15 @@ static void binder_transaction(struct binder_proc *proc,
 		 * process and is put in a pending queue, waiting for the target
 		 * process to be unfrozen.
 		 */
-		if (return_error == BR_TRANSACTION_PENDING_FROZEN)
+		if (return_error == BR_TRANSACTION_PENDING_FROZEN) {
 			tcomplete->type = BINDER_WORK_TRANSACTION_PENDING;
+			if (binder_genl_report_enabled(proc, BINDER_GENL_FLAG_DELAYED))
+				binder_genl_send_report(context, return_error,
+							proc->pid, thread->pid,
+							target_proc ? target_proc->pid : 0,
+							target_thread ? target_thread->pid : 0,
+							reply, tr);
+		}
 		binder_enqueue_thread_work(thread, tcomplete);
 		if (return_error &&
 		    return_error != BR_TRANSACTION_PENDING_FROZEN)
@@ -3794,6 +3957,13 @@ static void binder_transaction(struct binder_proc *proc,
 		binder_dec_node_tmpref(target_node);
 	}
 
+	if (binder_genl_report_enabled(proc, BINDER_GENL_FLAG_FAILED))
+		binder_genl_send_report(context, return_error,
+					proc->pid, thread->pid,
+					target_proc ? target_proc->pid : 0,
+					target_thread ? target_thread->pid : 0,
+					reply, tr);
+
 	binder_debug(BINDER_DEBUG_FAILED_TRANSACTION,
 		     "%d:%d transaction %s to %d:%d failed %d/%d/%d, size %lld-%lld line %d\n",
 		     proc->pid, thread->pid, reply ? "reply" :
@@ -6114,6 +6284,11 @@ static int binder_release(struct inode *nodp, struct file *filp)
 
 	binder_defer_work(proc, BINDER_DEFERRED_RELEASE);
 
+	if (proc->pid == proc->context->report_portid) {
+		proc->context->report_portid = 0;
+		proc->context->report_flags = 0;
+	}
+
 	return 0;
 }
 
@@ -6311,6 +6486,94 @@ binder_defer_work(struct binder_proc *proc, enum binder_deferred_state defer)
 	mutex_unlock(&binder_deferred_lock);
 }
 
+/**
+ * binder_genl_nl_set_doit() - .doit handler for BINDER_GENL_CMD_SET
+ * @skb:	the metadata struct passed from netlink driver
+ * @info:	the generic netlink struct passed from netlink driver
+ *
+ * Implements the .doit function to process binder genl commands.
+ */
+int binder_genl_nl_set_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	int payload;
+	int portid;
+	u32 pid;
+	u32 flags;
+	void *hdr;
+	struct binder_device *device;
+	struct binder_context *context = NULL;
+
+	if (GENL_REQ_ATTR_CHECK(info, BINDER_GENL_A_CMD_CONTEXT) ||
+	    GENL_REQ_ATTR_CHECK(info, BINDER_GENL_A_CMD_PID) ||
+	    GENL_REQ_ATTR_CHECK(info, BINDER_GENL_A_CMD_FLAGS))
+		return -EINVAL;
+
+	hlist_for_each_entry(device, &binder_devices, hlist) {
+		if (!nla_strcmp(info->attrs[BINDER_GENL_A_CMD_CONTEXT],
+				device->context.name)) {
+			context = &device->context;
+			break;
+		}
+	}
+
+	if (!context) {
+		NL_SET_ERR_MSG(info->extack, "Unknown binder context\n");
+		return -EINVAL;
+	}
+
+	portid = nlmsg_hdr(skb)->nlmsg_pid;
+	pid = nla_get_u32(info->attrs[BINDER_GENL_A_CMD_PID]);
+	flags = nla_get_u32(info->attrs[BINDER_GENL_A_CMD_FLAGS]);
+
+	if (context->report_portid && context->report_portid != portid) {
+		NL_SET_ERR_MSG_FMT(info->extack,
+				   "No permission to set flags from %d\n",
+				   portid);
+		return -EPERM;
+	}
+
+	if (binder_genl_set_report(context, pid, flags) < 0) {
+		pr_err("Failed to set report flags %u for %u\n", flags, pid);
+		return -EINVAL;
+	}
+
+	payload = nla_total_size(sizeof(pid)) + nla_total_size(sizeof(flags));
+	skb = genlmsg_new(payload + GENL_HDRLEN, GFP_KERNEL);
+	if (!skb) {
+		pr_err("Failed to alloc binder genl reply message\n");
+		return -ENOMEM;
+	}
+
+	hdr = genlmsg_iput(skb, info);
+	if (!hdr)
+		goto free_skb;
+
+	if (nla_put_string(skb, BINDER_GENL_A_CMD_CONTEXT, context->name) ||
+	    nla_put_u32(skb, BINDER_GENL_A_CMD_PID, pid) ||
+	    nla_put_u32(skb, BINDER_GENL_A_CMD_FLAGS, flags))
+		goto cancel_skb;
+
+	genlmsg_end(skb, hdr);
+
+	if (genlmsg_reply(skb, info)) {
+		pr_err("Failed to send binder genl reply message\n");
+		return -EFAULT;
+	}
+
+	if (!context->report_portid)
+		context->report_portid = portid;
+
+	return 0;
+
+cancel_skb:
+	pr_err("Failed to add reply attributes to binder genl message\n");
+	genlmsg_cancel(skb, hdr);
+free_skb:
+	pr_err("Free binder genl reply message on error\n");
+	nlmsg_free(skb);
+	return -EMSGSIZE;
+}
+
 static void print_binder_transaction_ilocked(struct seq_file *m,
 					     struct binder_proc *proc,
 					     const char *prefix,
@@ -6894,6 +7157,17 @@ const struct binder_debugfs_entry binder_debugfs_entries[] = {
 	{} /* terminator */
 };
 
+/**
+ * Add a binder device to binder_devices
+ * @device: the new binder device to add to the global list
+ *
+ * Not reentrant as the list is not protected by any locks
+ */
+void binder_add_device(struct binder_device *device)
+{
+	hlist_add_head(&device->hlist, &binder_devices);
+}
+
 static int __init init_binder_device(const char *name)
 {
 	int ret;
@@ -6919,6 +7193,7 @@ static int __init init_binder_device(const char *name)
 	}
 
 	hlist_add_head(&binder_device->hlist, &binder_devices);
+	binder_device->context.report_seq = (atomic_t)ATOMIC_INIT(0);
 
 	return ret;
 }
@@ -6975,6 +7250,12 @@ static int __init binder_init(void)
 	if (ret)
 		goto err_init_binder_device_failed;
 
+	ret = genl_register_family(&binder_genl_nl_family);
+	if (ret) {
+		pr_err("Failed to register binder genl family\n");
+		goto err_init_binder_device_failed;
+	}
+
 	return ret;
 
 err_init_binder_device_failed:
diff --git a/drivers/android/binder_genl.c b/drivers/android/binder_genl.c
new file mode 100644
index 000000000000..29d79bdd9649
--- /dev/null
+++ b/drivers/android/binder_genl.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)
+/* Do not edit directly, auto-generated from: */
+/*	Documentation/netlink/specs/binder_genl.yaml */
+/* YNL-GEN kernel source */
+
+#include <net/netlink.h>
+#include <net/genetlink.h>
+
+#include "binder_genl.h"
+
+#include <uapi/linux/android/binder_genl.h>
+
+/* BINDER_GENL_CMD_SET - do */
+static const struct nla_policy binder_genl_set_nl_policy[BINDER_GENL_A_CMD_FLAGS + 1] = {
+	[BINDER_GENL_A_CMD_CONTEXT] = { .type = NLA_NUL_STRING, },
+	[BINDER_GENL_A_CMD_PID] = { .type = NLA_U32, },
+	[BINDER_GENL_A_CMD_FLAGS] = NLA_POLICY_MASK(NLA_U32, 0xf),
+};
+
+/* Ops table for binder_genl */
+static const struct genl_split_ops binder_genl_nl_ops[] = {
+	{
+		.cmd		= BINDER_GENL_CMD_SET,
+		.doit		= binder_genl_nl_set_doit,
+		.policy		= binder_genl_set_nl_policy,
+		.maxattr	= BINDER_GENL_A_CMD_FLAGS,
+		.flags		= GENL_CMD_CAP_DO,
+	},
+};
+
+struct genl_family binder_genl_nl_family __ro_after_init = {
+	.name		= BINDER_GENL_FAMILY_NAME,
+	.version	= BINDER_GENL_FAMILY_VERSION,
+	.netnsok	= true,
+	.parallel_ops	= true,
+	.module		= THIS_MODULE,
+	.split_ops	= binder_genl_nl_ops,
+	.n_split_ops	= ARRAY_SIZE(binder_genl_nl_ops),
+};
diff --git a/drivers/android/binder_genl.h b/drivers/android/binder_genl.h
new file mode 100644
index 000000000000..9d68c155b7c4
--- /dev/null
+++ b/drivers/android/binder_genl.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) */
+/* Do not edit directly, auto-generated from: */
+/*	Documentation/netlink/specs/binder_genl.yaml */
+/* YNL-GEN kernel header */
+
+#ifndef _LINUX_BINDER_GENL_GEN_H
+#define _LINUX_BINDER_GENL_GEN_H
+
+#include <net/netlink.h>
+#include <net/genetlink.h>
+
+#include <uapi/linux/android/binder_genl.h>
+
+int binder_genl_nl_set_doit(struct sk_buff *skb, struct genl_info *info);
+
+extern struct genl_family binder_genl_nl_family;
+
+#endif /* _LINUX_BINDER_GENL_GEN_H */
diff --git a/drivers/android/binder_internal.h b/drivers/android/binder_internal.h
index f8d6be682f23..cc745367a519 100644
--- a/drivers/android/binder_internal.h
+++ b/drivers/android/binder_internal.h
@@ -12,21 +12,35 @@
 #include <linux/stddef.h>
 #include <linux/types.h>
 #include <linux/uidgid.h>
+#include <net/genetlink.h>
 #include <uapi/linux/android/binderfs.h>
 #include "binder_alloc.h"
 #include "dbitmap.h"
 
+/**
+ * struct binder_context - information about a binder domain
+ * @binder_context_mgr_node: the context manager
+ * @context_mgr_node_lock:   the lock protecting the above context manager node
+ * @binder_context_mgr_uid:  the uid of the above context manager
+ * @name:                    the name of the binder device
+ * @report_portid:           the netlink socket to receive binder reports
+ * @report_flags:            the categories of binder transactions that would
+ *                           be reported (see enum binder_report_flag).
+ * @report_seq:              the seq number of the generic netlink report
+ */
 struct binder_context {
 	struct binder_node *binder_context_mgr_node;
 	struct mutex context_mgr_node_lock;
 	kuid_t binder_context_mgr_uid;
 	const char *name;
+	u32 report_portid;
+	u32 report_flags;
+	atomic_t report_seq;
 };
 
 /**
  * struct binder_device - information about a binder device node
- * @hlist:          list of binder devices (only used for devices requested via
- *                  CONFIG_ANDROID_BINDER_DEVICES)
+ * @hlist:          list of binder devices
  * @miscdev:        information about a binder character device node
  * @context:        binder context information
  * @binderfs_inode: This is the inode of the root dentry of the super block
@@ -415,6 +429,8 @@ struct binder_ref {
  * @binderfs_entry:       process-specific binderfs log file
  * @oneway_spam_detection_enabled: process enabled oneway spam detection
  *                        or not
+ * @report_flags:         the categories of binder transactions that would
+ *                        be reported (see enum binder_genl_flag).
  *
  * Bookkeeping structure for binder processes
  */
@@ -453,6 +469,7 @@ struct binder_proc {
 	spinlock_t outer_lock;
 	struct dentry *binderfs_entry;
 	bool oneway_spam_detection_enabled;
+	u32 report_flags;
 };
 
 /**
@@ -582,4 +599,10 @@ struct binder_object {
 	};
 };
 
+/**
+ * Add a binder device to binder_devices
+ * @device: the new binder device to add to the global list
+ */
+void binder_add_device(struct binder_device *device);
+
 #endif /* _LINUX_BINDER_INTERNAL_H */
diff --git a/drivers/android/binder_trace.h b/drivers/android/binder_trace.h
index fe38c6fc65d0..551b6c9d9f73 100644
--- a/drivers/android/binder_trace.h
+++ b/drivers/android/binder_trace.h
@@ -423,6 +423,41 @@ TRACE_EVENT(binder_return,
 			  "unknown")
 );
 
+TRACE_EVENT(binder_send_report,
+	TP_PROTO(const char *name, u32 err, u32 pid, u32 tid, u32 to_pid,
+		 u32 to_tid, u32 reply, struct binder_transaction_data *tr),
+	TP_ARGS(name, err, pid, tid, to_pid, to_tid, reply, tr),
+	TP_STRUCT__entry(
+		__field(const char *, name)
+		__field(u32, err)
+		__field(u32, pid)
+		__field(u32, tid)
+		__field(u32, to_pid)
+		__field(u32, to_tid)
+		__field(u32, reply)
+		__field(u32, flags)
+		__field(u32, code)
+		__field(binder_size_t, data_size)
+	),
+	TP_fast_assign(
+		__entry->name = name;
+		__entry->err = err;
+		__entry->pid = pid;
+		__entry->tid = tid;
+		__entry->to_pid = to_pid;
+		__entry->to_tid = to_tid;
+		__entry->reply = reply;
+		__entry->flags = tr->flags;
+		__entry->code = tr->code;
+		__entry->data_size = tr->data_size;
+	),
+	TP_printk("%s: %d %d:%d -> %d:%d %s flags=0x08%x code=%d %llu",
+		  __entry->name, __entry->err, __entry->pid, __entry->tid,
+		  __entry->to_pid, __entry->to_tid,
+		  __entry->reply ? "reply" : "",
+		  __entry->flags, __entry->code, __entry->data_size)
+);
+
 #endif /* _BINDER_TRACE_H */
 
 #undef TRACE_INCLUDE_PATH
diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c
index ad1fa7abc323..bc6bae76ccaf 100644
--- a/drivers/android/binderfs.c
+++ b/drivers/android/binderfs.c
@@ -207,6 +207,8 @@ static int binderfs_binder_device_create(struct inode *ref_inode,
 	fsnotify_create(root->d_inode, dentry);
 	inode_unlock(d_inode(root));
 
+	binder_add_device(device);
+
 	return 0;
 
 err:
diff --git a/include/uapi/linux/android/binder_genl.h b/include/uapi/linux/android/binder_genl.h
new file mode 100644
index 000000000000..f39b5c81e477
--- /dev/null
+++ b/include/uapi/linux/android/binder_genl.h
@@ -0,0 +1,55 @@
+/* SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) */
+/* Do not edit directly, auto-generated from: */
+/*	Documentation/netlink/specs/binder_genl.yaml */
+/* YNL-GEN uapi header */
+
+#ifndef _UAPI_LINUX_ANDROID_BINDER_GENL_H
+#define _UAPI_LINUX_ANDROID_BINDER_GENL_H
+
+#define BINDER_GENL_FAMILY_NAME		"binder_genl"
+#define BINDER_GENL_FAMILY_VERSION	1
+
+/*
+ * Define what kind of binder transactions should be reported.
+ */
+enum binder_genl_flag {
+	BINDER_GENL_FLAG_FAILED = 1,
+	BINDER_GENL_FLAG_DELAYED = 2,
+	BINDER_GENL_FLAG_SPAM = 4,
+	BINDER_GENL_FLAG_OVERRIDE = 8,
+};
+
+enum {
+	BINDER_GENL_A_CMD_CONTEXT = 1,
+	BINDER_GENL_A_CMD_PID,
+	BINDER_GENL_A_CMD_FLAGS,
+
+	__BINDER_GENL_A_CMD_MAX,
+	BINDER_GENL_A_CMD_MAX = (__BINDER_GENL_A_CMD_MAX - 1)
+};
+
+enum {
+	BINDER_GENL_A_REPORT_CONTEXT = 1,
+	BINDER_GENL_A_REPORT_ERR,
+	BINDER_GENL_A_REPORT_FROM_PID,
+	BINDER_GENL_A_REPORT_FROM_TID,
+	BINDER_GENL_A_REPORT_TO_PID,
+	BINDER_GENL_A_REPORT_TO_TID,
+	BINDER_GENL_A_REPORT_REPLY,
+	BINDER_GENL_A_REPORT_FLAGS,
+	BINDER_GENL_A_REPORT_CODE,
+	BINDER_GENL_A_REPORT_DATA_SIZE,
+
+	__BINDER_GENL_A_REPORT_MAX,
+	BINDER_GENL_A_REPORT_MAX = (__BINDER_GENL_A_REPORT_MAX - 1)
+};
+
+enum {
+	BINDER_GENL_CMD_SET = 1,
+	BINDER_GENL_CMD_REPORT,
+
+	__BINDER_GENL_CMD_MAX,
+	BINDER_GENL_CMD_MAX = (__BINDER_GENL_CMD_MAX - 1)
+};
+
+#endif /* _UAPI_LINUX_ANDROID_BINDER_GENL_H */
-- 
2.47.0.277.g8800431eea-goog

Re: [PATCH net-next v8 2/2] binder: report txn errors via generic netlink

[kernel test robot]

Hi Li,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 31a1f8752f7df7e3d8122054fbef02a9a8bff38f]

url:    https://github.com/intel-lab-lkp/linux/commits/Li-Li/tools-ynl-gen-allow-uapi-headers-in-sub-dirs/20241114-033521
base:   31a1f8752f7df7e3d8122054fbef02a9a8bff38f
patch link:    https://lore.kernel.org/r/20241113193239.2113577-3-dualli%40chromium.org
patch subject: [PATCH net-next v8 2/2] binder: report txn errors via generic netlink
config: arc-randconfig-001-20241117 (https://download.01.org/0day-ci/archive/20241117/202411171514.Vfp0RaLK-lkp@intel.com/config)
compiler: arceb-elf-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241117/202411171514.Vfp0RaLK-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202411171514.Vfp0RaLK-lkp@intel.com/

All warnings (new ones prefixed by >>):

   drivers/android/binder.c:1977: warning: Function parameter or struct member 'file' not described in 'binder_task_work_cb'
   drivers/android/binder.c:1977: warning: Excess struct member 'fd' description in 'binder_task_work_cb'
   drivers/android/binder.c:2428: warning: Function parameter or struct member 'offset' not described in 'binder_ptr_fixup'
   drivers/android/binder.c:2428: warning: Function parameter or struct member 'skip_size' not described in 'binder_ptr_fixup'
   drivers/android/binder.c:2428: warning: Function parameter or struct member 'fixup_data' not described in 'binder_ptr_fixup'
   drivers/android/binder.c:2428: warning: Function parameter or struct member 'node' not described in 'binder_ptr_fixup'
   drivers/android/binder.c:2448: warning: Function parameter or struct member 'offset' not described in 'binder_sg_copy'
   drivers/android/binder.c:2448: warning: Function parameter or struct member 'sender_uaddr' not described in 'binder_sg_copy'
   drivers/android/binder.c:2448: warning: Function parameter or struct member 'length' not described in 'binder_sg_copy'
   drivers/android/binder.c:2448: warning: Function parameter or struct member 'node' not described in 'binder_sg_copy'
   drivers/android/binder.c:4180: warning: Function parameter or struct member 'thread' not described in 'binder_free_buf'
>> drivers/android/binder.c:7161: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
    * Add a binder device to binder_devices


vim +7161 drivers/android/binder.c

  7159	
  7160	/**
> 7161	 * Add a binder device to binder_devices
  7162	 * @device: the new binder device to add to the global list
  7163	 *
  7164	 * Not reentrant as the list is not protected by any locks
  7165	 */
  7166	void binder_add_device(struct binder_device *device)
  7167	{
  7168		hlist_add_head(&device->hlist, &binder_devices);
  7169	}
  7170	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH net-next v8 0/2] binder: report txn errors via generic netlink

[Jakub Kicinski]

On Wed, 13 Nov 2024 11:32:37 -0800 Li Li wrote:
> Jakub Kicinski (1):
>   tools: ynl-gen: allow uapi headers in sub-dirs

I'll take a look at your code later in the week (the merge window 
has started), but I'll apply patch 1 (AKA my own patch) already.
Fewer potential cross-tree conflicts.

Re: [PATCH net-next v8 0/2] binder: report txn errors via generic netlink

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Wed, 13 Nov 2024 11:32:37 -0800 you wrote:
> From: Li Li <dualli@google.com>
> 
> It's a known issue that neither the frozen processes nor the system
> administration process of the OS can correctly deal with failed binder
> transactions. The reason is that there's no reliable way for the user
> space administration process to fetch the binder errors from the kernel
> binder driver.
> 
> [...]

Here is the summary with links:
  - [net-next,v8,1/2] tools: ynl-gen: allow uapi headers in sub-dirs
    https://git.kernel.org/netdev/net-next/c/6204656478be
  - [net-next,v8,2/2] binder: report txn errors via generic netlink
    (no matching commit)

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Re: [PATCH net-next v8 2/2] binder: report txn errors via generic netlink

[Jakub Kicinski]

On Wed, 13 Nov 2024 11:32:39 -0800 Li Li wrote:
> +/**
> + * binder_find_proc() - set binder report flags
> + * @pid:	the target process
> + */
> +static struct binder_proc *binder_find_proc(int pid)
> +{
> +	struct binder_proc *proc;
> +
> +	mutex_lock(&binder_procs_lock);
> +	hlist_for_each_entry(proc, &binder_procs, proc_node) {
> +		if (proc->pid == pid) {
> +			mutex_unlock(&binder_procs_lock);
> +			return proc;
> +		}
> +	}
> +	mutex_unlock(&binder_procs_lock);
> +
> +	return NULL;
> +}
> +
> +/**
> + * binder_genl_set_report() - set binder report flags
> + * @context:	the binder context to set the flags
> + * @pid:	the target process
> + * @flags:	the flags to set
> + *
> + * If pid is 0, the flags are applied to the whole binder context.
> + * Otherwise, the flags are applied to the specific process only.
> + */
> +static int binder_genl_set_report(struct binder_context *context, u32 pid,
> +				  u32 flags)
> +{
> +	struct binder_proc *proc;
> +
> +	if (flags != (flags & (BINDER_GENL_FLAG_OVERRIDE
> +			| BINDER_GENL_FLAG_FAILED
> +			| BINDER_GENL_FLAG_DELAYED
> +			| BINDER_GENL_FLAG_SPAM))) {
> +		pr_err("Invalid binder report flags: %u\n", flags);
> +		return -EINVAL;

no need, netlink already checks that only bits from the flags are used:

                                    vvvvvvvvvvvvvvvvvvvvvvvvvvvvv
+	[BINDER_GENL_A_CMD_FLAGS] = NLA_POLICY_MASK(NLA_U32, 0xf),

> +	}
> +
> +	if (!pid) {
> +		/* Set the global flags for the whole binder context */
> +		context->report_flags = flags;
> +	} else {
> +		/* Set the per-process flags */
> +		proc = binder_find_proc(pid);
> +		if (!proc) {
> +			pr_err("Invalid binder report pid %u\n", pid);
> +			return -EINVAL;
> +		}
> +
> +		proc->report_flags = flags;
> +	}
> +
> +	return 0;
> +}

> +static void binder_genl_send_report(struct binder_context *context, u32 err,
> +				    u32 pid, u32 tid, u32 to_pid, u32 to_tid,
> +				    u32 reply,
> +				    struct binder_transaction_data *tr)
> +{
> +	int payload;
> +	int ret;
> +	struct sk_buff *skb;
> +	void *hdr;
> +
> +	trace_binder_send_report(context->name, err, pid, tid, to_pid, to_tid,
> +				 reply, tr);
> +
> +	payload = nla_total_size(strlen(context->name) + 1) +
> +		  nla_total_size(sizeof(u32)) * (BINDER_GENL_A_REPORT_MAX - 1);
> +	skb = genlmsg_new(payload + GENL_HDRLEN, GFP_KERNEL);

 genlmsg_new() adds the GENL_HDRLEN already

> +	if (!skb) {
> +		pr_err("Failed to alloc binder genl message\n");
> +		return;
> +	}
> +
> +	hdr = genlmsg_put(skb, 0, atomic_inc_return(&context->report_seq),
> +			  &binder_genl_nl_family, 0, BINDER_GENL_CMD_REPORT);
> +	if (!hdr)
> +		goto free_skb;
> +
> +	if (nla_put_string(skb, BINDER_GENL_A_REPORT_CONTEXT, context->name) ||
> +	    nla_put_u32(skb, BINDER_GENL_A_REPORT_ERR, err) ||
> +	    nla_put_u32(skb, BINDER_GENL_A_REPORT_FROM_PID, pid) ||
> +	    nla_put_u32(skb, BINDER_GENL_A_REPORT_FROM_TID, tid) ||
> +	    nla_put_u32(skb, BINDER_GENL_A_REPORT_TO_PID, to_pid) ||
> +	    nla_put_u32(skb, BINDER_GENL_A_REPORT_TO_TID, to_tid) ||
> +	    nla_put_u32(skb, BINDER_GENL_A_REPORT_REPLY, reply) ||
> +	    nla_put_u32(skb, BINDER_GENL_A_REPORT_FLAGS, tr->flags) ||
> +	    nla_put_u32(skb, BINDER_GENL_A_REPORT_CODE, tr->code) ||
> +	    nla_put_u32(skb, BINDER_GENL_A_REPORT_DATA_SIZE, tr->data_size))
> +		goto cancel_skb;
> +
> +	genlmsg_end(skb, hdr);
> +
> +	ret = genlmsg_unicast(&init_net, skb, context->report_portid);
> +	if (ret < 0)
> +		pr_err("Failed to send binder genl message to %d: %d\n",
> +		       context->report_portid, ret);
> +	return;
> +
> +cancel_skb:
> +	pr_err("Failed to add report attributes to binder genl message\n");
> +	genlmsg_cancel(skb, hdr);
> +free_skb:
> +	pr_err("Free binder genl report message on error\n");
> +	nlmsg_free(skb);
> +}

> +/**
> + * binder_genl_nl_set_doit() - .doit handler for BINDER_GENL_CMD_SET
> + * @skb:	the metadata struct passed from netlink driver
> + * @info:	the generic netlink struct passed from netlink driver
> + *
> + * Implements the .doit function to process binder genl commands.
> + */
> +int binder_genl_nl_set_doit(struct sk_buff *skb, struct genl_info *info)
> +{
> +	int payload;
> +	int portid;
> +	u32 pid;
> +	u32 flags;
> +	void *hdr;
> +	struct binder_device *device;
> +	struct binder_context *context = NULL;
> +
> +	if (GENL_REQ_ATTR_CHECK(info, BINDER_GENL_A_CMD_CONTEXT) ||
> +	    GENL_REQ_ATTR_CHECK(info, BINDER_GENL_A_CMD_PID) ||
> +	    GENL_REQ_ATTR_CHECK(info, BINDER_GENL_A_CMD_FLAGS))
> +		return -EINVAL;
> +
> +	hlist_for_each_entry(device, &binder_devices, hlist) {
> +		if (!nla_strcmp(info->attrs[BINDER_GENL_A_CMD_CONTEXT],
> +				device->context.name)) {
> +			context = &device->context;
> +			break;
> +		}
> +	}
> +
> +	if (!context) {
> +		NL_SET_ERR_MSG(info->extack, "Unknown binder context\n");
> +		return -EINVAL;
> +	}
> +
> +	portid = nlmsg_hdr(skb)->nlmsg_pid;
> +	pid = nla_get_u32(info->attrs[BINDER_GENL_A_CMD_PID]);
> +	flags = nla_get_u32(info->attrs[BINDER_GENL_A_CMD_FLAGS]);
> +
> +	if (context->report_portid && context->report_portid != portid) {
> +		NL_SET_ERR_MSG_FMT(info->extack,
> +				   "No permission to set flags from %d\n",
> +				   portid);
> +		return -EPERM;
> +	}
> +
> +	if (binder_genl_set_report(context, pid, flags) < 0) {
> +		pr_err("Failed to set report flags %u for %u\n", flags, pid);
> +		return -EINVAL;
> +	}
> +
> +	payload = nla_total_size(sizeof(pid)) + nla_total_size(sizeof(flags));
> +	skb = genlmsg_new(payload + GENL_HDRLEN, GFP_KERNEL);
> +	if (!skb) {
> +		pr_err("Failed to alloc binder genl reply message\n");
> +		return -ENOMEM;

no need for error messages on allocation failures, kernel will print an
OOM report

> +	}
> +
> +	hdr = genlmsg_iput(skb, info);
> +	if (!hdr)
> +		goto free_skb;
> +
> +	if (nla_put_string(skb, BINDER_GENL_A_CMD_CONTEXT, context->name) ||

Have you counted strlen(context->name) to payload?
TBH for small messages counting payload size is probably an overkill,
you can use NLMSG_GOODSIZE as the size of the skb.

> +	    nla_put_u32(skb, BINDER_GENL_A_CMD_PID, pid) ||
> +	    nla_put_u32(skb, BINDER_GENL_A_CMD_FLAGS, flags))
> +		goto cancel_skb;
> +
> +	genlmsg_end(skb, hdr);
> +
> +	if (genlmsg_reply(skb, info)) {
> +		pr_err("Failed to send binder genl reply message\n");
> +		return -EFAULT;
> +	}
> +
> +	if (!context->report_portid)
> +		context->report_portid = portid;

Is there any locking required?

> +	return 0;
> +
> +cancel_skb:
> +	pr_err("Failed to add reply attributes to binder genl message\n");
> +	genlmsg_cancel(skb, hdr);
> +free_skb:
> +	pr_err("Free binder genl reply message on error\n");
> +	nlmsg_free(skb);
> +	return -EMSGSIZE;
> +}

Re: [PATCH net-next v8 2/2] binder: report txn errors via generic netlink

[Li Li]

On Wed, Dec 4, 2024 at 6:35 PM Jakub Kicinski <kuba@kernel.org> wrote:
>
> On Wed, 13 Nov 2024 11:32:39 -0800 Li Li wrote:
> > +     struct binder_proc *proc;
> > +
> > +     if (flags != (flags & (BINDER_GENL_FLAG_OVERRIDE
> > +                     | BINDER_GENL_FLAG_FAILED
> > +                     | BINDER_GENL_FLAG_DELAYED
> > +                     | BINDER_GENL_FLAG_SPAM))) {
> > +             pr_err("Invalid binder report flags: %u\n", flags);
> > +             return -EINVAL;
>
> no need, netlink already checks that only bits from the flags are used:

Ah, yes, let me remove this redundant check.

>
>                                     vvvvvvvvvvvvvvvvvvvvvvvvvvvvv
> +       [BINDER_GENL_A_CMD_FLAGS] = NLA_POLICY_MASK(NLA_U32, 0xf),
>

> > +     payload = nla_total_size(strlen(context->name) + 1) +
> > +               nla_total_size(sizeof(u32)) * (BINDER_GENL_A_REPORT_MAX - 1);
> > +     skb = genlmsg_new(payload + GENL_HDRLEN, GFP_KERNEL);
>
>  genlmsg_new() adds the GENL_HDRLEN already
>

Yes, genlmsg_new calls genlmsg_msg_size to include GENL_HDRLEN already.
I'll just use NLMSG_DEFAULT_SIZE as suggested below.

> > +     payload = nla_total_size(sizeof(pid)) + nla_total_size(sizeof(flags));
> > +     skb = genlmsg_new(payload + GENL_HDRLEN, GFP_KERNEL);
> > +     if (!skb) {
> > +             pr_err("Failed to alloc binder genl reply message\n");
> > +             return -ENOMEM;
>
> no need for error messages on allocation failures, kernel will print an
> OOM report
>

Will remove this unnecessary pr_err.

> > +     }
> > +
> > +     hdr = genlmsg_iput(skb, info);
> > +     if (!hdr)
> > +             goto free_skb;
> > +
> > +     if (nla_put_string(skb, BINDER_GENL_A_CMD_CONTEXT, context->name) ||
>
> Have you counted strlen(context->name) to payload?
> TBH for small messages counting payload size is probably an overkill,
> you can use NLMSG_GOODSIZE as the size of the skb.
>

Yes, the message is known to be small. I'll use GENLMSG_DEFAULT_SIZE instead.

> > +         nla_put_u32(skb, BINDER_GENL_A_CMD_PID, pid) ||
> > +         nla_put_u32(skb, BINDER_GENL_A_CMD_FLAGS, flags))
> > +             goto cancel_skb;
> > +
> > +     genlmsg_end(skb, hdr);
> > +
> > +     if (genlmsg_reply(skb, info)) {
> > +             pr_err("Failed to send binder genl reply message\n");
> > +             return -EFAULT;
> > +     }
> > +
> > +     if (!context->report_portid)
> > +             context->report_portid = portid;
>
> Is there any locking required?

A lock isn't necessary here. The system administration process always runs
before any other user apps. Even though this is not true, the design is to
allow the first process to claim this netlink. Having a lock doesn't help
in any case.

>
> > +     return 0;
> > +
> > +cancel_skb:
> > +     pr_err("Failed to add reply attributes to binder genl message\n");
> > +     genlmsg_cancel(skb, hdr);
> > +free_skb:
> > +     pr_err("Free binder genl reply message on error\n");
> > +     nlmsg_free(skb);
> > +     return -EMSGSIZE;
> > +}
>

Re: [PATCH net-next v8 2/2] binder: report txn errors via generic netlink

[Jakub Kicinski]

On Thu, 5 Dec 2024 04:01:01 -0800 Li Li wrote:
> The system administration process always runs before any other user apps.

I don't wanna comment on that, since I don't know binder.
Perhaps you could add a comment to flag this to binder reviewers?
I want it to be clear that netlink provides no concurrency protection.