| Message ID | 20190622000358.19895-7-matthewgarrett@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Lockdown as an LSM | expand |
On Fri, Jun 21, 2019 at 05:03:35PM -0700, Matthew Garrett wrote: > From: Matthew Garrett <mjg59@srcf.ucam.org> > > 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> Reviewed-by: Kees Cook <keescook@chromium.org> -Kees > Signed-off-by: Matthew Garrett <mjg59@google.com> > Acked-by: Dave Young <dyoung@redhat.com> > cc: kexec@lists.infradead.org > --- > include/linux/security.h | 1 + > kernel/kexec.c | 8 ++++++++ > security/lockdown/lockdown.c | 1 + > 3 files changed, 10 insertions(+) > > diff --git a/include/linux/security.h b/include/linux/security.h > index 200175c8605a..00a31ab2e5ba 100644 > --- a/include/linux/security.h > +++ b/include/linux/security.h > @@ -84,6 +84,7 @@ enum lockdown_reason { > LOCKDOWN_NONE, > LOCKDOWN_MODULE_SIGNATURE, > LOCKDOWN_DEV_MEM, > + LOCKDOWN_KEXEC, > LOCKDOWN_INTEGRITY_MAX, > LOCKDOWN_CONFIDENTIALITY_MAX, > }; > diff --git a/kernel/kexec.c b/kernel/kexec.c > index 68559808fdfa..ec3f07a4b1c0 100644 > --- a/kernel/kexec.c > +++ b/kernel/kexec.c > @@ -207,6 +207,14 @@ static inline int kexec_load_check(unsigned long nr_segments, > if (result < 0) > 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 > * This leaves us room for future extensions. > diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c > index 565c87451f0f..08fcd8116db3 100644 > --- a/security/lockdown/lockdown.c > +++ b/security/lockdown/lockdown.c > @@ -20,6 +20,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = { > [LOCKDOWN_NONE] = "none", > [LOCKDOWN_MODULE_SIGNATURE] = "unsigned module loading", > [LOCKDOWN_DEV_MEM] = "/dev/mem,kmem,port", > + [LOCKDOWN_KEXEC] = "kexec of unsigned images", > [LOCKDOWN_INTEGRITY_MAX] = "integrity", > [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", > }; > -- > 2.22.0.410.gd8fdbe21b5-goog >
diff --git a/include/linux/security.h b/include/linux/security.h index 200175c8605a..00a31ab2e5ba 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -84,6 +84,7 @@ enum lockdown_reason { LOCKDOWN_NONE, LOCKDOWN_MODULE_SIGNATURE, LOCKDOWN_DEV_MEM, + LOCKDOWN_KEXEC, LOCKDOWN_INTEGRITY_MAX, LOCKDOWN_CONFIDENTIALITY_MAX, }; diff --git a/kernel/kexec.c b/kernel/kexec.c index 68559808fdfa..ec3f07a4b1c0 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -207,6 +207,14 @@ static inline int kexec_load_check(unsigned long nr_segments, if (result < 0) 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 * This leaves us room for future extensions. diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c index 565c87451f0f..08fcd8116db3 100644 --- a/security/lockdown/lockdown.c +++ b/security/lockdown/lockdown.c @@ -20,6 +20,7 @@ static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = { [LOCKDOWN_NONE] = "none", [LOCKDOWN_MODULE_SIGNATURE] = "unsigned module loading", [LOCKDOWN_DEV_MEM] = "/dev/mem,kmem,port", + [LOCKDOWN_KEXEC] = "kexec of unsigned images", [LOCKDOWN_INTEGRITY_MAX] = "integrity", [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", };