Message-ID: <2025121632-CVE-2025-68183-f588@gregkh>
Date: Tue, 16 Dec 2025 14:43:44 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2025-68183: ima: don't clear IMA_DIGSIG flag when setting or removing non-IMA xattr

From: Greg Kroah-Hartman <gregkh@...nel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

ima: don't clear IMA_DIGSIG flag when setting or removing non-IMA xattr

Currently when both IMA and EVM are in fix mode, the IMA signature will
be reset to IMA hash if a program first stores IMA signature in
security.ima and then writes/removes some other security xattr for the
file.

For example, on Fedora, after booting the kernel with "ima_appraise=fix
evm=fix ima_policy=appraise_tcb" and installing rpm-plugin-ima,
installing/reinstalling a package will not make good reference IMA
signature generated. Instead IMA hash is generated,

    # getfattr -m - -d -e hex /usr/bin/bash
    # file: usr/bin/bash
    security.ima=0x0404...

This happens because when setting security.selinux, the IMA_DIGSIG flag
that had been set early was cleared. As a result, IMA hash is generated
when the file is closed.

Similarly, IMA signature can be cleared on file close after removing
security xattr like security.evm or setting/removing ACL.

Prevent replacing the IMA file signature with a file hash, by preventing
the IMA_DIGSIG flag from being reset.

Here's a minimal C reproducer which sets security.selinux as the last
step which can also replaced by removing security.evm or setting ACL,

    #include <stdio.h>
    #include <sys/xattr.h>
    #include <fcntl.h>
    #include <unistd.h>
    #include <string.h>
    #include <stdlib.h>

    int main() {
        const char* file_path = "/usr/sbin/test_binary";
        const char* hex_string = "030204d33204490066306402304";
        int length = strlen(hex_string);
        char* ima_attr_value;
        int fd;

        fd = open(file_path, O_WRONLY|O_CREAT|O_EXCL, 0644);
        if (fd == -1) {
            perror("Error opening file");
            return 1;
        }

        ima_attr_value = (char*)malloc(length / 2 );
        for (int i = 0, j = 0; i < length; i += 2, j++) {
            sscanf(hex_string + i, "%2hhx", &ima_attr_value[j]);
        }

        if (fsetxattr(fd, "security.ima", ima_attr_value, length/2, 0) == -1) {
            perror("Error setting extended attribute");
            close(fd);
            return 1;
        }

        const char* selinux_value= "system_u:object_r:bin_t:s0";
        if (fsetxattr(fd, "security.selinux", selinux_value, strlen(selinux_value), 0) == -1) {
            perror("Error setting extended attribute");
            close(fd);
            return 1;
        }

        close(fd);

        return 0;
    }

The Linux kernel CVE team has assigned CVE-2025-68183 to this issue.


Affected and fixed versions
===========================

	Fixed in 6.6.117 with commit d2993a7e98eb70c737c6f5365a190e79c72b8407
	Fixed in 6.12.58 with commit edd824eb45e4f7e05ad3ab090dab6dbdb79cd292
	Fixed in 6.17.8 with commit 02aa671c08a4834bef5166743a7b88686fbfa023
	Fixed in 6.18 with commit 88b4cbcf6b041ae0f2fc8a34554a5b6a83a2b7cd

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2025-68183
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	security/integrity/ima/ima_appraise.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/d2993a7e98eb70c737c6f5365a190e79c72b8407
	https://git.kernel.org/stable/c/edd824eb45e4f7e05ad3ab090dab6dbdb79cd292
	https://git.kernel.org/stable/c/02aa671c08a4834bef5166743a7b88686fbfa023
	https://git.kernel.org/stable/c/88b4cbcf6b041ae0f2fc8a34554a5b6a83a2b7cd

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