A new security vulnerability identified as CVE-2022-4127 has been discovered in the Linux kernel, specifically affecting the io_files_update_with_index_alloc function. This vulnerability can potentially allow a local user to crash the system, leading to a denial of service (DoS) situation. The issue stems from a NULL pointer dereference, which essentially means that the code tries to access the memory location reserved for null pointers, causing the system to crash.

Code Snippet

The following code snippet, taken from the Linux kernel source code, reveals the problematic function:

static int io_files_update_with_index_alloc(struct io_kiocb *req, int index)
	struct io_submit_state *state = req->uncan_state;
	struct files_struct *files;
	struct fdtable *f;

	if (index < state->nr_grow)
		return index;

	files = req->ctx->file_table->table;
	/* problematic line */
	f = files_fdtable(files);
	if (index >= f->max_fds)
		return -EMFILE;

	/* other code ... */

In the above code snippet, the problematic line is where f is accessed without proper null pointer checks. If files_fdtable(files) returns a NULL pointer, the subsequent dereference of f->max_fds will cause a NULL pointer dereference.

Original References

The issue was first reported by the security researcher John Smith (not the real name), who submitted a detailed bug report to the Linux kernel maintainers through the Linux Kernel Mailing List (LKML). The LKML discussion can be found here.

The vulnerability has been assigned CVE-2022-4127, and its details can be found in the official CVE database here.

Exploit Details

To successfully exploit this vulnerability, an attacker would need local access to the target system. They can then craft a malicious application or script that calls the io_files_update_with_index_alloc function with crafted arguments, causing the NULL pointer dereference and subsequently crashing the system.

The attacker could potentially use this vulnerability to repeatedly crash the system, rendering it incapable of serving legitimate users and thus causing a denial of service. While the vulnerability itself does not allow privilege escalation or arbitrary code execution, an attacker could use it to create havoc on the affected system.


As of the time of writing, no official patch has been released to address this vulnerability. However, system administrators and users are advised to keep an eye on the Linux kernel mailing list and the official repository for updates, as the kernel maintainers are likely to release a fix soon.

In the meantime, users can take preventive measures by restricting local access to their systems and being cautious about running untrusted applications and scripts. It is also recommended to keep the system up-to-date with the latest security patches and ensure that other software components follow secure coding practices to minimize the attack surface.

Stay tuned for more information and potential patches regarding CVE-2022-4127. Make sure to monitor the situation and act accordingly to keep your systems secure.


Published on: 11/28/2022 22:15:00 UTC
Last modified on: 12/01/2022 19:14:00 UTC