From: Coiby Xu <coxu@redhat.com>
To: kexec@lists.infradead.org
Cc: Matthew Garrett <mjg59@srcf.ucam.org>,
Jiri Bohac <jbohac@suse.cz>, David Howells <dhowells@redhat.com>,
linux-integrity@vger.kernel.org,
Eric Biederman <ebiederm@xmission.com>,
James Morris <jmorris@namei.org>,
Matthew Garrett <mjg59@google.com>,
linux-kernel@vger.kernel.org (open list)
Subject: [PATCH] lockdown: kexec_file: prevent unsigned kernel image when KEXEC_SIG not enabled
Date: Mon, 21 Nov 2022 15:29:47 +0800 [thread overview]
Message-ID: <20221121072947.836672-1-coxu@redhat.com> (raw)
A kernel builder may not enable KEXEC_SIG and some architectures like
ppc64 simply don't have KEXEC_SIG. In these cases, unless both
IMA_ARCH_POLICY and secure boot also enabled, lockdown doesn't prevent
unsigned kernel image from being kexec'ed via the kexec_file_load
syscall whereas it could prevent one via the kexec_load syscall. Mandate
signature verification for those cases.
Fixes: 155bdd30af17 ("kexec_file: Restrict at runtime if the kernel is locked down")
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Jiri Bohac <jbohac@suse.cz>
Cc: David Howells <dhowells@redhat.com>
Cc: kexec@lists.infradead.org
Cc: linux-integrity@vger.kernel.org
Signed-off-by: Coiby Xu <coxu@redhat.com>
---
kernel/kexec_file.c | 31 +++++++++++++++++++++----------
1 file changed, 21 insertions(+), 10 deletions(-)
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 45637511e0de..04d56b6e6459 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -125,6 +125,20 @@ void kimage_file_post_load_cleanup(struct kimage *image)
image->image_loader_data = NULL;
}
+static int mandate_signatute_verification(void)
+{
+ /*
+ * If IMA is guaranteed to appraise a signature on the kexec
+ * image, permit it even if the kernel is otherwise locked
+ * down.
+ */
+ if (!ima_appraise_signature(READING_KEXEC_IMAGE) &&
+ security_locked_down(LOCKDOWN_KEXEC))
+ return -EPERM;
+
+ return 0;
+}
+
#ifdef CONFIG_KEXEC_SIG
#ifdef CONFIG_SIGNED_PE_FILE_VERIFICATION
int kexec_kernel_verify_pe_sig(const char *kernel, unsigned long kernel_len)
@@ -168,14 +182,9 @@ kimage_validate_signature(struct kimage *image)
return ret;
}
- /*
- * If IMA is guaranteed to appraise a signature on the kexec
- * image, permit it even if the kernel is otherwise locked
- * down.
- */
- if (!ima_appraise_signature(READING_KEXEC_IMAGE) &&
- security_locked_down(LOCKDOWN_KEXEC))
- return -EPERM;
+ ret = mandate_signatute_verification();
+ if (ret)
+ return ret;
pr_debug("kernel signature verification failed (%d).\n", ret);
}
@@ -211,10 +220,12 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
#ifdef CONFIG_KEXEC_SIG
ret = kimage_validate_signature(image);
-
+#else
+ ret = mandate_signatute_verification();
+#endif
if (ret)
goto out;
-#endif
+
/* It is possible that there no initramfs is being loaded */
if (!(flags & KEXEC_FILE_NO_INITRAMFS)) {
ret = kernel_read_file_from_fd(initrd_fd, 0, &image->initrd_buf,
--
2.38.1
next reply other threads:[~2022-11-21 7:31 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-21 7:29 Coiby Xu [this message]
2022-11-21 18:23 ` [PATCH] lockdown: kexec_file: prevent unsigned kernel image when KEXEC_SIG not enabled Mimi Zohar
2022-11-22 2:36 ` Coiby Xu
2022-11-28 17:16 ` Mimi Zohar
2022-12-30 7:00 ` Coiby Xu
2022-11-22 2:28 ` [PATCH v2] " Coiby Xu
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