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kernel: Use task work to install fd #2905

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Merged
aviraxp merged 1 commit into from
Nov 10, 2025
Merged

kernel: Use task work to install fd #2905

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41 changes: 37 additions & 4 deletions kernel/supercalls.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4,10 +4,13 @@
#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>

Expand Down Expand Up @@ -464,6 +467,28 @@ static const struct ksu_ioctl_cmd_map ksu_ioctl_handlers[] = {
{ .cmd = 0, .name = NULL, .handler = NULL, .perm_check = NULL } // Sentinel
};

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);
}

static int reboot_handler_pre(struct kprobe *p, struct pt_regs *regs)
{
Expand All @@ -474,12 +499,20 @@ static int reboot_handler_pre(struct kprobe *p, struct pt_regs *regs)

// Check if this is a request to install KSU fd
if (magic1 == KSU_INSTALL_MAGIC1 && magic2 == KSU_INSTALL_MAGIC2) {
int fd = ksu_install_fd();
pr_info("[%d] install ksu fd: %d\n", current->pid, fd);
struct ksu_install_fd_tw *tw;

arg4 = (unsigned long)PT_REGS_SYSCALL_PARM4(real_regs);
if (copy_to_user((int *)arg4, &fd, sizeof(fd))) {
pr_err("install ksu fd reply err\n");

tw = kzalloc(sizeof(*tw), GFP_ATOMIC);
if (!tw)
return 0;

tw->outp = (int __user *)arg4;
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");
}
}

Expand Down