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kernel: Allow to re-enable sucompat
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@tiann
tiann committed Feb 16, 2025
1 parent 9bb39ff commit 4593ae8
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Showing 2 changed files with 45 additions and 39 deletions.
81 changes: 44 additions & 37 deletions kernel/sucompat.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -191,7 +191,7 @@ int ksu_handle_devpts(struct inode *inode)

#ifdef CONFIG_KPROBES

static int sys_faccessat_handler_pre(struct kprobe *p, struct pt_regs *regs)
static int faccessat_handler_pre(struct kprobe *p, struct pt_regs *regs)
{
struct pt_regs *real_regs = PT_REAL_REGS(regs);
int *dfd = (int *)&PT_REGS_PARM1(real_regs);
Expand All @@ -202,17 +202,18 @@ static int sys_faccessat_handler_pre(struct kprobe *p, struct pt_regs *regs)
return ksu_handle_faccessat(dfd, filename_user, mode, NULL);
}

static int sys_newfstatat_handler_pre(struct kprobe *p, struct pt_regs *regs)
static int newfstatat_handler_pre(struct kprobe *p, struct pt_regs *regs)
{
struct pt_regs *real_regs = PT_REAL_REGS(regs);
int *dfd = (int *)&PT_REGS_PARM1(real_regs);
const char __user **filename_user = (const char **)&PT_REGS_PARM2(real_regs);
const char __user **filename_user =
(const char **)&PT_REGS_PARM2(real_regs);
int *flags = (int *)&PT_REGS_SYSCALL_PARM4(real_regs);

return ksu_handle_stat(dfd, filename_user, flags);
}

static int sys_execve_handler_pre(struct kprobe *p, struct pt_regs *regs)
static int execve_handler_pre(struct kprobe *p, struct pt_regs *regs)
{
struct pt_regs *real_regs = PT_REAL_REGS(regs);
const char __user **filename_user =
Expand All @@ -222,21 +223,6 @@ static int sys_execve_handler_pre(struct kprobe *p, struct pt_regs *regs)
NULL);
}

static struct kprobe faccessat_kp = {
.symbol_name = SYS_FACCESSAT_SYMBOL,
.pre_handler = sys_faccessat_handler_pre,
};

static struct kprobe newfstatat_kp = {
.symbol_name = SYS_NEWFSTATAT_SYMBOL,
.pre_handler = sys_newfstatat_handler_pre,
};

static struct kprobe execve_kp = {
.symbol_name = SYS_EXECVE_SYMBOL,
.pre_handler = sys_execve_handler_pre,
};

static int pts_unix98_lookup_pre(struct kprobe *p, struct pt_regs *regs)
{
struct inode *inode;
Expand All @@ -246,35 +232,56 @@ static int pts_unix98_lookup_pre(struct kprobe *p, struct pt_regs *regs)
return ksu_handle_devpts(inode);
}

static struct kprobe pts_unix98_lookup_kp = { .symbol_name =
"pts_unix98_lookup",
.pre_handler =
pts_unix98_lookup_pre };

#endif

static struct kprobe *init_kprobe(const char *name,
kprobe_pre_handler_t handler)
{
struct kprobe *kp = kzalloc(sizeof(struct kprobe), GFP_KERNEL);
if (!kp)
return NULL;
kp->symbol_name = name;
kp->pre_handler = handler;

int ret = register_kprobe(kp);
pr_info("sucompat: register_%s kprobe: %d\n", name, ret);
if (ret) {
kfree(kp);
return NULL;
}

return kp;
}

static void destroy_kprobe(struct kprobe **kp_ptr)
{
struct kprobe *kp = *kp_ptr;
if (!kp)
return;
unregister_kprobe(kp);
synchronize_rcu();
kfree(kp);
*kp_ptr = NULL;
}

static struct kprobe *su_kps[4];

// sucompat: permited process can execute 'su' to gain root access.
void ksu_sucompat_init()
{
#ifdef CONFIG_KPROBES
int ret;
ret = register_kprobe(&execve_kp);
pr_info("sucompat: execve_kp: %d\n", ret);
ret = register_kprobe(&newfstatat_kp);
pr_info("sucompat: newfstatat_kp: %d\n", ret);
ret = register_kprobe(&faccessat_kp);
pr_info("sucompat: faccessat_kp: %d\n", ret);
ret = register_kprobe(&pts_unix98_lookup_kp);
pr_info("sucompat: devpts_kp: %d\n", ret);
su_kps[0] = init_kprobe(SYS_EXECVE_SYMBOL, execve_handler_pre);
su_kps[1] = init_kprobe(SYS_FACCESSAT_SYMBOL, faccessat_handler_pre);
su_kps[2] = init_kprobe(SYS_NEWFSTATAT_SYMBOL, newfstatat_handler_pre);
su_kps[3] = init_kprobe("pts_unix98_lookup", pts_unix98_lookup_pre);
#endif
}

void ksu_sucompat_exit()
{
#ifdef CONFIG_KPROBES
unregister_kprobe(&execve_kp);
unregister_kprobe(&newfstatat_kp);
unregister_kprobe(&faccessat_kp);
unregister_kprobe(&pts_unix98_lookup_kp);
for (int i = 0; i < ARRAY_SIZE(su_kps); i++) {
destroy_kprobe(&su_kps[i]);
}
#endif
}
3 changes: 1 addition & 2 deletions manager/app/src/main/java/me/weishu/kernelsu/ui/screen/Settings.kt
View file
Original file line number Diff line number Diff line change
Expand Up @@ -181,7 +181,6 @@ fun SettingScreen(navigator: DestinationsNavigator) {
title = stringResource(id = R.string.settings_disable_su),
summary = stringResource(id = R.string.settings_disable_su_summary),
checked = isSuDisabled,
enabled = !isSuDisabled // we can't re-enable su if it's disabled.

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@backslashxx

backslashxx Feb 17, 2025 •
edited
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Contributor

oh keks, it is here, it got lost.
) { checked ->
val shouldEnable = !checked
if (Natives.setSuEnabled(shouldEnable)) {
Expand Down Expand Up @@ -502,4 +501,4 @@ private fun TopBar(
@Composable
private fun SettingsPreview() {
SettingScreen(EmptyDestinationsNavigator)
}
}

3 comments on commit 4593ae8

@backslashxx
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@backslashxx backslashxx commented on 4593ae8 Feb 17, 2025 •
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This is a neat feature. Works great.

will this feature eventually be per-app?
might be neat to actually put on app profile.

say something like Termux needs sucompat, but not KernelFlasher.

@tiann
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@tiann tiann commented on 4593ae8 Feb 17, 2025

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Maybe not. This feature is used for resisting side channel attack.
Adding per-app feature can't achieve it.

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@backslashxx backslashxx commented on 4593ae8 Feb 19, 2025 •
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I tried adding sucompat init and exit on __ksu_is_allow_uid conditions, so what happens
is that when a non-allowed app runs in background, it just turns off sucompat

yeah its a no go. I only realized it now, that, that question was dumb.

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