All of
 help / color / mirror / Atom feed
From: "tip-bot2 for Michael Roth" <>
Cc: Jeremi Piotrowski <>,, Michael Roth <>,
	Borislav Petkov <>,,,
Subject: [tip: x86/urgent] x86/boot: Don't propagate uninitialized boot_params->cc_blob_address
Date: Wed, 24 Aug 2022 07:55:47 -0000	[thread overview]
Message-ID: <166132774791.401.13991431396549405975.tip-bot2@tip-bot2> (raw)
In-Reply-To: <>

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     4b1c742407571eff58b6de9881889f7ca7c4b4dc
Author:        Michael Roth <>
AuthorDate:    Tue, 23 Aug 2022 11:07:34 -05:00
Committer:     Borislav Petkov <>
CommitterDate: Wed, 24 Aug 2022 09:03:04 +02:00

x86/boot: Don't propagate uninitialized boot_params->cc_blob_address

In some cases, bootloaders will leave boot_params->cc_blob_address
uninitialized rather than zeroing it out. This field is only meant to be
set by the boot/compressed kernel in order to pass information to the
uncompressed kernel when SEV-SNP support is enabled.

Therefore, there are no cases where the bootloader-provided values
should be treated as anything other than garbage. Otherwise, the
uncompressed kernel may attempt to access this bogus address, leading to
a crash during early boot.

Normally, sanitize_boot_params() would be used to clear out such fields
but that happens too late: sev_enable() may have already initialized
it to a valid value that should not be zeroed out. Instead, have
sev_enable() zero it out unconditionally beforehand.

Also ensure this happens for !CONFIG_AMD_MEM_ENCRYPT as well by also
including this handling in the sev_enable() stub function.

  [ bp: Massage commit message and comments. ]

Fixes: b190a043c49a ("x86/sev: Add SEV-SNP feature detection/setup")
Reported-by: Jeremi Piotrowski <>
Signed-off-by: Michael Roth <>
Signed-off-by: Borislav Petkov <>
 arch/x86/boot/compressed/misc.h | 12 +++++++++++-
 arch/x86/boot/compressed/sev.c  |  8 ++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 4910bf2..62208ec 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -132,7 +132,17 @@ void snp_set_page_private(unsigned long paddr);
 void snp_set_page_shared(unsigned long paddr);
 void sev_prep_identity_maps(unsigned long top_level_pgt);
-static inline void sev_enable(struct boot_params *bp) { }
+static inline void sev_enable(struct boot_params *bp)
+	/*
+	 * bp->cc_blob_address should only be set by boot/compressed kernel.
+	 * Initialize it to 0 unconditionally (thus here in this stub too) to
+	 * ensure that uninitialized values from buggy bootloaders aren't
+	 * propagated.
+	 */
+	if (bp)
+		bp->cc_blob_address = 0;
 static inline void sev_es_shutdown_ghcb(void) { }
 static inline bool sev_es_check_ghcb_fault(unsigned long address)
diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index 52f989f..c93930d 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -277,6 +277,14 @@ void sev_enable(struct boot_params *bp)
 	bool snp;
+	 * bp->cc_blob_address should only be set by boot/compressed kernel.
+	 * Initialize it to 0 to ensure that uninitialized values from
+	 * buggy bootloaders aren't propagated.
+	 */
+	if (bp)
+		bp->cc_blob_address = 0;
+	/*
 	 * Setup/preliminary detection of SNP. This will be sanity-checked
 	 * against CPUID/MSR values later.

      parent reply	other threads:[~2022-08-24  7:56 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-23 16:07 [PATCH] x86/boot: Don't propagate uninitialized boot_params->cc_blob_address Michael Roth
2022-08-23 17:11 ` Borislav Petkov
2022-08-24  7:55 ` tip-bot2 for Michael Roth [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=166132774791.401.13991431396549405975.tip-bot2@tip-bot2 \ \ \ \ \ \ \ \ \ \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.