ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 137 insertions, 0 deletions

diff --git a/drivers/pci/syscall.c b/drivers/pci/syscall.c
new file mode 100644
index 000000000..803acbf33
--- /dev/null
+++ b/drivers/pci/syscall.c
@@ -0,0 +1,137 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * For architectures where we want to allow direct access to the PCI config
+ * stuff - it would probably be preferable on PCs too, but there people
+ * just do it by hand with the magic northbridge registers.
+ */
+
+#include <linux/errno.h>
+#include <linux/pci.h>
+#include <linux/security.h>
+#include <linux/syscalls.h>
+#include <linux/uaccess.h>
+#include "pci.h"
+
+SYSCALL_DEFINE5(pciconfig_read, unsigned long, bus, unsigned long, dfn,
+		unsigned long, off, unsigned long, len, void __user *, buf)
+{
+	struct pci_dev *dev;
+	u8 byte;
+	u16 word;
+	u32 dword;
+	int err, cfg_ret;
+
+	err = -EPERM;
+	dev = NULL;
+	if (!capable(CAP_SYS_ADMIN))
+		goto error;
+
+	err = -ENODEV;
+	dev = pci_get_domain_bus_and_slot(0, bus, dfn);
+	if (!dev)
+		goto error;
+
+	switch (len) {
+	case 1:
+		cfg_ret = pci_user_read_config_byte(dev, off, &byte);
+		break;
+	case 2:
+		cfg_ret = pci_user_read_config_word(dev, off, &word);
+		break;
+	case 4:
+		cfg_ret = pci_user_read_config_dword(dev, off, &dword);
+		break;
+	default:
+		err = -EINVAL;
+		goto error;
+	}
+
+	err = -EIO;
+	if (cfg_ret)
+		goto error;
+
+	switch (len) {
+	case 1:
+		err = put_user(byte, (u8 __user *)buf);
+		break;
+	case 2:
+		err = put_user(word, (u16 __user *)buf);
+		break;
+	case 4:
+		err = put_user(dword, (u32 __user *)buf);
+		break;
+	}
+	pci_dev_put(dev);
+	return err;
+
+error:
+	/* ??? XFree86 doesn't even check the return value.  They
+	   just look for 0xffffffff in the output, since that's what
+	   they get instead of a machine check on x86.  */
+	switch (len) {
+	case 1:
+		put_user(-1, (u8 __user *)buf);
+		break;
+	case 2:
+		put_user(-1, (u16 __user *)buf);
+		break;
+	case 4:
+		put_user(-1, (u32 __user *)buf);
+		break;
+	}
+	pci_dev_put(dev);
+	return err;
+}
+
+SYSCALL_DEFINE5(pciconfig_write, unsigned long, bus, unsigned long, dfn,
+		unsigned long, off, unsigned long, len, void __user *, buf)
+{
+	struct pci_dev *dev;
+	u8 byte;
+	u16 word;
+	u32 dword;
+	int err = 0;
+
+	if (!capable(CAP_SYS_ADMIN) ||
+	    security_locked_down(LOCKDOWN_PCI_ACCESS))
+		return -EPERM;
+
+	dev = pci_get_domain_bus_and_slot(0, bus, dfn);
+	if (!dev)
+		return -ENODEV;
+
+	switch (len) {
+	case 1:
+		err = get_user(byte, (u8 __user *)buf);
+		if (err)
+			break;
+		err = pci_user_write_config_byte(dev, off, byte);
+		if (err)
+			err = -EIO;
+		break;
+
+	case 2:
+		err = get_user(word, (u16 __user *)buf);
+		if (err)
+			break;
+		err = pci_user_write_config_word(dev, off, word);
+		if (err)
+			err = -EIO;
+		break;
+
+	case 4:
+		err = get_user(dword, (u32 __user *)buf);
+		if (err)
+			break;
+		err = pci_user_write_config_dword(dev, off, dword);
+		if (err)
+			err = -EIO;
+		break;
+
+	default:
+		err = -EINVAL;
+		break;
+	}
+	pci_dev_put(dev);
+	return err;
+}