The following commit has been merged into the x86/urgent branch of tip:
Commit-ID: 4b1c742407571eff58b6de9881889f7ca7c4b4dc Gitweb: https://git.kernel.org/tip/4b1c742407571eff58b6de9881889f7ca7c4b4dc Author: Michael Roth michael.roth@amd.com AuthorDate: Tue, 23 Aug 2022 11:07:34 -05:00 Committer: Borislav Petkov bp@suse.de 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 jpiotrowski@linux.microsoft.com Reported-by: watnuss@gmx.de Signed-off-by: Michael Roth michael.roth@amd.com Signed-off-by: Borislav Petkov bp@suse.de Cc: stable@vger.kernel.org Link: https://bugzilla.kernel.org/show_bug.cgi?id=216387 Link: https://lore.kernel.org/r/20220823160734.89036-1-michael.roth@amd.com --- 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); #else -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. */