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kexec_load: Disable at runtime if the kernel is locked down

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The kexec_load() syscall permits the loading and execution of arbitrary
code in ring 0, which is something that lock-down is meant to prevent. It
makes sense to disable kexec_load() in this situation.

This does not affect kexec_file_load() syscall which can check for a
signature on the image to be booted.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Matthew Garrett <mjg59@google.com>
Acked-by: Dave Young <dyoung@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
cc: kexec@lists.infradead.org
Signed-off-by: James Morris <jmorris@namei.org>
This commit is contained in:
Matthew Garrett 2019-08-19 17:17:42 -07:00 committed by James Morris
parent 9b9d8dda1e
commit 7d31f4602f
3 changed files with 10 additions and 0 deletions
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1
include/linux/security.h
View File

@ -105,6 +105,7 @@ enum lockdown_reason {
LOCKDOWN_NONE, LOCKDOWN_NONE,
LOCKDOWN_MODULE_SIGNATURE, LOCKDOWN_MODULE_SIGNATURE,
LOCKDOWN_DEV_MEM, LOCKDOWN_DEV_MEM,
LOCKDOWN_KEXEC,
LOCKDOWN_INTEGRITY_MAX, LOCKDOWN_INTEGRITY_MAX,
LOCKDOWN_CONFIDENTIALITY_MAX, LOCKDOWN_CONFIDENTIALITY_MAX,
}; };

8
kernel/kexec.c
View File

@ -205,6 +205,14 @@ static inline int kexec_load_check(unsigned long nr_segments,
if (result < 0) if (result < 0)
return result; return result;
/*
* kexec can be used to circumvent module loading restrictions, so
* prevent loading in that case
*/
result = security_locked_down(LOCKDOWN_KEXEC);
if (result)
return result;
/* /*
* Verify we have a legal set of flags * Verify we have a legal set of flags
* This leaves us room for future extensions. * This leaves us room for future extensions.

1
security/lockdown/lockdown.c
View File

@ -20,6 +20,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = {
[LOCKDOWN_NONE] = "none", [LOCKDOWN_NONE] = "none",
[LOCKDOWN_MODULE_SIGNATURE] = "unsigned module loading", [LOCKDOWN_MODULE_SIGNATURE] = "unsigned module loading",
[LOCKDOWN_DEV_MEM] = "/dev/mem,kmem,port", [LOCKDOWN_DEV_MEM] = "/dev/mem,kmem,port",
[LOCKDOWN_KEXEC] = "kexec of unsigned images",
[LOCKDOWN_INTEGRITY_MAX] = "integrity", [LOCKDOWN_INTEGRITY_MAX] = "integrity",
[LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality",
}; };