From c25cb9aa4b668aed82ed056edbf85af16ae51f95 Mon Sep 17 00:00:00 2001
From: Rifat Azad <rifat.44.azad.rifs@gmail.com>
Date: Wed, 18 Dec 2024 21:34:04 +0600
Subject: [PATCH] kernel: auto backport path_umount to fs/namespace.c at build
 time

---
 kernel/Makefile | 43 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 42 insertions(+), 1 deletion(-)

diff --git a/kernel/Makefile b/kernel/Makefile
index bf9522b6..e8415786 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -71,8 +71,49 @@ ccflags-y += -DEXPECTED_HASH=\"$(KSU_EXPECTED_HASH)\"
 ccflags-y += -DEXPECTED_NEXT_SIZE=$(KSU_NEXT_EXPECTED_SIZE)
 ccflags-y += -DEXPECTED_NEXT_HASH=\"$(KSU_NEXT_EXPECTED_HASH)\"
 
-ifeq ($(shell grep -q "int path_umount" $(srctree)/fs/namespace.c; echo $$?),0)
 ccflags-y += -DKSU_UMOUNT
+
+ifneq ($(shell grep -Eq "^static int can_umount" $(srctree)/fs/namespace.c; echo $$?),0)
+$(info -- KSU_NEXT: adding function 'static int can_umount(const struct path *path, int flags);' to $(srctree)/fs/namespace.c)
+CAN_UMOUNT = static int can_umount(const struct path *path, int flags)\n\
+{\n\t\
+        struct mount *mnt = real_mount(path->mnt);\n\t\
+        if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))\n\t\t\
+                return -EINVAL;\n\t\
+        if (!may_mount())\n\t\t\
+                return -EPERM;\n\t\
+        if (path->dentry != path->mnt->mnt_root)\n\t\t\
+                return -EINVAL;\n\t\
+        if (!check_mnt(mnt))\n\t\t\
+                return -EINVAL;\n\t\
+        if (mnt->mnt.mnt_flags & MNT_LOCKED)\n\t\t\
+                return -EINVAL;\n\t\
+        if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN))\n\t\t\
+                return -EPERM;\n\t\
+        return 0;\n\
+}\n
+$(shell sed -i '/^static bool is_mnt_ns_file/i $(CAN_UMOUNT)' $(srctree)/fs/namespace.c;)
+endif
+
+ifneq ($(shell grep -Eq "^int path_umount" $(srctree)/fs/namespace.c; echo $$?),0)
+$(info -- KSU_NEXT: adding function 'int path_umount(struct path *path, int flags);' to $(srctree)/fs/namespace.c)
+PATH_UMOUNT = int path_umount(struct path *path, int flags)\n\
+{\n\t\
+        struct mount *mnt = real_mount(path->mnt);\n\t\
+        int ret;\n\t\
+        ret = can_umount(path, flags);\n\t\
+        if (!ret)\n\t\t\
+                ret = do_umount(mnt, flags);\n\t\
+        dput(path->dentry);\n\t\
+        mntput_no_expire(mnt);\n\t\
+        return ret;\n\
+}\n
+$(shell sed -i '/^static bool is_mnt_ns_file/i $(PATH_UMOUNT)' $(srctree)/fs/namespace.c;)
+endif
+
+ifneq ($(shell grep -Eq "^int path_umount" $(srctree)/fs/internal.h; echo $$?),0)
+$(shell sed -i '/^extern void __init mnt_init/a int path_umount(struct path *path, int flags);' $(srctree)/fs/internal.h;)
+$(info -- KSU_NEXT: adding 'int path_umount(struct path *path, int flags);' to $(srctree)/fs/internal.h)
 endif
 
 ccflags-y += -Wno-implicit-function-declaration -Wno-strict-prototypes -Wno-int-conversion -Wno-gcc-compat