Add a patch for compat input in 64 bit apps

.github/workflows/build-aarch64.yml → .github/workflows/cross-build-aarch64.yml

@@ -1,10 +1,10 @@
-name: Build aarch64 kernel
+name: Cross-build aarch64 kernel
 on: [pull_request, create]
 
 jobs:
   build:
     if: github.event_name == 'pull_request'
-    name: Build aarch64 kernel
+    name: Cross-build aarch64 kernel
     runs-on: ubuntu-latest
     steps:
       - name: Code checkout

Makefile

@@ -6,8 +6,8 @@ KERNEL_PATCHES = $(shell find patches/ -name "0*.patch" | sort)
 KERNEL_C_BUNDLE = kernel.c
 
 ABI_VERSION = 4
-FULL_VERSION = 4.4.1
-TIMESTAMP = "Thu Sep 26 16:00:58 CEST 2024"
+FULL_VERSION = 4.4.2
+TIMESTAMP = "Tue Oct  8 13:02:33 CEST 2024"
 
 KERNEL_FLAGS = KBUILD_BUILD_TIMESTAMP=$(TIMESTAMP)
 KERNEL_FLAGS += KBUILD_BUILD_USER=root

patches/0018-Enable-64-bit-processes-to-use-compat-input-syscalls.patch

@@ -0,0 +1,124 @@
+From 897560fd00e1add63a9973c31fc437b006855680 Mon Sep 17 00:00:00 2001
+From: Sergio Lopez <[email protected]>
+Date: Tue, 8 Oct 2024 11:24:25 +0200
+Subject: [PATCH] Enable 64 bit processes to use compat input syscalls
+
+The compat variant of input syscalls is only enabled for 32 bit
+tasks, but in some cases, such as userspace emulation, it's useful to
+enable that variant for 64 bit processes.
+
+Here we introduce the PR_[GET|SET]_COMPAT_INPUT prctl to allow 64 bit
+tasks to opt-in for compat input syscalls.
+
+Signed-off-by: Sergio Lopez <[email protected]>
+---
+ drivers/input/input-compat.c |  6 +++---
+ drivers/input/input-compat.h |  2 +-
+ include/linux/sched.h        |  5 +++++
+ include/uapi/linux/prctl.h   |  5 +++++
+ kernel/sys.c                 | 15 +++++++++++++++
+ 5 files changed, 29 insertions(+), 4 deletions(-)
+
+diff --git a/drivers/input/input-compat.c b/drivers/input/input-compat.c
+index 2ccd3eedbd67..abb8cfb99d6c 100644
+--- a/drivers/input/input-compat.c
++++ b/drivers/input/input-compat.c
+@@ -14,7 +14,7 @@
+ int input_event_from_user(const char __user *buffer,
+ 			  struct input_event *event)
+ {
+-	if (in_compat_syscall() && !COMPAT_USE_64BIT_TIME) {
++	if (current->compat_input || (in_compat_syscall() && !COMPAT_USE_64BIT_TIME)) {
+ 		struct input_event_compat compat_event;
+
+ 		if (copy_from_user(&compat_event, buffer,
+@@ -38,7 +38,7 @@ int input_event_from_user(const char __user *buffer,
+ int input_event_to_user(char __user *buffer,
+ 			const struct input_event *event)
+ {
+-	if (in_compat_syscall() && !COMPAT_USE_64BIT_TIME) {
++	if (current->compat_input || (in_compat_syscall() && !COMPAT_USE_64BIT_TIME)) {
+ 		struct input_event_compat compat_event;
+
+ 		compat_event.sec = event->input_event_sec;
+@@ -62,7 +62,7 @@ int input_event_to_user(char __user *buffer,
+ int input_ff_effect_from_user(const char __user *buffer, size_t size,
+ 			      struct ff_effect *effect)
+ {
+-	if (in_compat_syscall()) {
++	if (current->compat_input || (in_compat_syscall() && !COMPAT_USE_64BIT_TIME)) {
+ 		struct ff_effect_compat *compat_effect;
+
+ 		if (size != sizeof(struct ff_effect_compat))
+diff --git a/drivers/input/input-compat.h b/drivers/input/input-compat.h
+index 3b7bb12b023b..e78c0492ce0d 100644
+--- a/drivers/input/input-compat.h
++++ b/drivers/input/input-compat.h
+@@ -53,7 +53,7 @@ struct ff_effect_compat {
+
+ static inline size_t input_event_size(void)
+ {
+-	return (in_compat_syscall() && !COMPAT_USE_64BIT_TIME) ?
++	return (current->compat_input || (in_compat_syscall() && !COMPAT_USE_64BIT_TIME)) ?
+ 		sizeof(struct input_event_compat) : sizeof(struct input_event);
+ }
+
+diff --git a/include/linux/sched.h b/include/linux/sched.h
+index 77f01ac385f7..01125573065e 100644
+--- a/include/linux/sched.h
++++ b/include/linux/sched.h
+@@ -1535,6 +1535,11 @@ struct task_struct {
+ #ifdef CONFIG_USER_EVENTS
+ 	struct user_event_mm		*user_event_mm;
+ #endif
++	/*
++	 * Whether the task wants to use compat input syscalls even if it's
++	 * a 64-bit process.
++	 */
++	bool compat_input;
+
+ 	/*
+ 	 * New fields for task_struct should be added above here, so that
+diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h
+index 961216093f11..86fca7d168cc 100644
+--- a/include/uapi/linux/prctl.h
++++ b/include/uapi/linux/prctl.h
+@@ -311,4 +311,9 @@ struct prctl_mm_map {
+ # define PR_SET_MEM_MODEL_DEFAULT	0
+ # define PR_SET_MEM_MODEL_TSO		1
+
++#define PR_GET_COMPAT_INPUT    0x63494e50
++#define PR_SET_COMPAT_INPUT    0x43494e50
++# define PR_SET_COMPAT_INPUT_DISABLE  0
++# define PR_SET_COMPAT_INPUT_ENABLE   1
++
+ #endif /* _LINUX_PRCTL_H */
+diff --git a/kernel/sys.c b/kernel/sys.c
+index 2db751ce25a2..1be74620b0b6 100644
+--- a/kernel/sys.c
++++ b/kernel/sys.c
+@@ -2768,6 +2768,21 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
+ 			return -EINVAL;
+ 		error = arch_prctl_mem_model_set(me, arg2);
+ 		break;
++	case PR_GET_COMPAT_INPUT:
++		if (arg2 || arg3 || arg4 || arg5)
++			return -EINVAL;
++		error = current->compat_input;
++		break;
++	case PR_SET_COMPAT_INPUT:
++		if (arg3 || arg4 || arg5)
++			return -EINVAL;
++		if (arg2 == PR_SET_COMPAT_INPUT_DISABLE)
++			current->compat_input = false;
++		else if (arg2 == PR_SET_COMPAT_INPUT_ENABLE)
++			current->compat_input = true;
++		else
++			return -EINVAL;
++		break;
+ 	default:
+ 		error = -EINVAL;
+ 		break;
+-- 
+2.46.0
+