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kernel: Use task work to install fd

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There are many fd related functions that can sleep, so we have no choice
but move operations to task work. Also close fd when copy_to_user fails.

Co-authored-by: Wang Han <416810799@qq.com>
This commit is contained in:
ShirkNeko
2025-11-11 01:10:36 +08:00
parent fd3a22360a
commit 8f49898155
1 changed files with 39 additions and 7 deletions
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46
kernel/supercalls.c
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@@ -4,12 +4,15 @@
#include <linux/capability.h>
#include <linux/cred.h>
#include <linux/err.h>
#include <linux/fdtable.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/kprobes.h>
#include <linux/syscalls.h>
#include <linux/task_work.h>
#include <linux/uaccess.h>
#include <linux/version.h>
#include <linux/kprobes.h>
#include "arch.h"
#include "allowlist.h"
@@ -739,9 +742,35 @@ static const struct ksu_ioctl_cmd_map ksu_ioctl_handlers[] = {
{ .cmd = 0, .name = NULL, .handler = NULL, .perm_check = NULL} // Sentine
};
#ifdef KSU_KPROBES_HOOK
struct ksu_install_fd_tw {
struct callback_head cb;
int __user *outp;
};
static void ksu_install_fd_tw_func(struct callback_head *cb)
{
struct ksu_install_fd_tw *tw = container_of(cb, struct ksu_install_fd_tw, cb);
int fd = ksu_install_fd();
pr_info("[%d] install ksu fd: %d\n", current->pid, fd);
if (copy_to_user(tw->outp, &fd, sizeof(fd))) {
pr_err("install ksu fd reply err\n");
#if LINUX_VERSION_CODE >= KERNEL_VERSION(5, 11, 0)
close_fd(fd);
#else
ksys_close(fd);
#endif
}
kfree(tw);
}
// downstream: make sure to pass arg as reference, this can allow us to extend things.
int ksu_handle_sys_reboot(int magic1, int magic2, unsigned int cmd, void __user **arg)
{
struct ksu_install_fd_tw *tw;
if (magic1 != KSU_INSTALL_MAGIC1)
return 0;
@@ -752,12 +781,16 @@ int ksu_handle_sys_reboot(int magic1, int magic2, unsigned int cmd, void __user
// Check if this is a request to install KSU fd
if (magic2 == KSU_INSTALL_MAGIC2) {
int fd = ksu_install_fd();
pr_info("[%d] install ksu fd: %d\n", current->pid, fd);
tw = kzalloc(sizeof(*tw), GFP_ATOMIC);
if (!tw)
return 0;
// downstream: dereference all arg usage!
if (copy_to_user((void __user *)*arg, &fd, sizeof(fd))) {
pr_err("install ksu fd reply err\n");
tw->outp = (int __user *)*arg;
tw->cb.func = ksu_install_fd_tw_func;
if (task_work_add(current, &tw->cb, TWA_RESUME)) {
kfree(tw);
pr_warn("install fd add task_work failed\n");
}
return 0;
@@ -768,7 +801,6 @@ int ksu_handle_sys_reboot(int magic1, int magic2, unsigned int cmd, void __user
return 0;
}
#ifdef KSU_KPROBES_HOOK
// Reboot hook for installing fd
static int reboot_handler_pre(struct kprobe *p, struct pt_regs *regs)
{