* [PATCH] kern/efi: Log a console error during a stack check failure
@ 2022-03-21 15:14 Chris Coulson
2022-03-22 17:05 ` Daniel Kiper
0 siblings, 1 reply; 3+ messages in thread
From: Chris Coulson @ 2022-03-21 15:14 UTC (permalink / raw)
To: grub-devel; +Cc: Chris Coulson
The initial implementation of the stack protector just busy looped
in __stack_chk_fail in order to reduce the amount of code being
executed after the stack has been compromised because of a lack of
firmware memory protections. With future firmware implementations
incorporating memory protections such as W^X, call in to boot services
when an error occurs in order to log a message to the console before
automatically rebooting the machine.
Signed-off-by: Chris Coulson <chris.coulson@canonical.com>
---
grub-core/Makefile.core.def | 4 +++-
grub-core/kern/efi/init.c | 23 +++++++++++++++++++++--
2 files changed, 24 insertions(+), 3 deletions(-)
diff --git a/grub-core/Makefile.core.def b/grub-core/Makefile.core.def
index ac00cc8a2..7e831d124 100644
--- a/grub-core/Makefile.core.def
+++ b/grub-core/Makefile.core.def
@@ -50,12 +50,14 @@ kernel = {
nostrip = emu;
emu_ldflags = '-Wl,-r';
+ i386_efi_cflags = '-fshort-wchar';
i386_efi_ldflags = '-Wl,-r';
i386_efi_stripflags = '--strip-unneeded -K start -R .note -R .comment -R .note.gnu.gold-version';
+ x86_64_efi_cflags = '-fshort-wchar';
x86_64_efi_ldflags = '-Wl,-r';
x86_64_efi_stripflags = '--strip-unneeded -K start -R .note -R .comment -R .note.gnu.gold-version';
- ia64_efi_cflags = '-fno-builtin -fpic -minline-int-divide-max-throughput';
+ ia64_efi_cflags = '-fshort-wchar -fno-builtin -fpic -minline-int-divide-max-throughput';
ia64_efi_ldflags = '-Wl,-r';
ia64_efi_stripflags = '--strip-unneeded -K start -R .note -R .comment -R .note.gnu.gold-version';
diff --git a/grub-core/kern/efi/init.c b/grub-core/kern/efi/init.c
index 7facacf09..7cb3f77e0 100644
--- a/grub-core/kern/efi/init.c
+++ b/grub-core/kern/efi/init.c
@@ -31,6 +31,11 @@
#ifdef GRUB_STACK_PROTECTOR
+static const grub_efi_char16_t stack_chk_fail_msg[] =
+ L"* GRUB: STACK SMASHING DETECTED!!! *\r\n"
+ L"* GRUB: ABORTED!!! *\r\n"
+ L"* GRUB: REBOOTING IN 5 SECONDS... *\r\n";
+
static grub_efi_guid_t rng_protocol_guid = GRUB_EFI_RNG_PROTOCOL_GUID;
/*
@@ -44,9 +49,23 @@ grub_addr_t __stack_chk_guard;
void __attribute__ ((noreturn))
__stack_chk_fail (void)
{
+ grub_efi_simple_text_output_interface_t *o;
+
+ /*
+ * Use ConOut here rather than StdErr. StdErr only goes to
+ * the serial console, at least on EDK2.
+ */
+ o = grub_efi_system_table->con_out;
+ efi_call_2 (o->output_string, o, stack_chk_fail_msg);
+
+ efi_call_1 (grub_efi_system_table->boot_services->stall, 5000000);
+ efi_call_4 (grub_efi_system_table->runtime_services->reset_system,
+ GRUB_EFI_RESET_SHUTDOWN, GRUB_EFI_ABORTED, 0, NULL);
+
/*
- * Assume it's not safe to call into EFI Boot Services. Sorry, that
- * means no console message here.
+ * We shouldn't get here. It's unsafe to return because the stack
+ * is compromised and this function is noreturn, so just busy
+ * loop forever.
*/
do
{
--
2.35.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] kern/efi: Log a console error during a stack check failure
2022-03-21 15:14 [PATCH] kern/efi: Log a console error during a stack check failure Chris Coulson
@ 2022-03-22 17:05 ` Daniel Kiper
2022-07-11 5:59 ` Glenn Washburn
0 siblings, 1 reply; 3+ messages in thread
From: Daniel Kiper @ 2022-03-22 17:05 UTC (permalink / raw)
To: Chris Coulson; +Cc: grub-devel
On Mon, Mar 21, 2022 at 03:14:39PM +0000, Chris Coulson wrote:
> The initial implementation of the stack protector just busy looped
> in __stack_chk_fail in order to reduce the amount of code being
> executed after the stack has been compromised because of a lack of
> firmware memory protections. With future firmware implementations
> incorporating memory protections such as W^X, call in to boot services
> when an error occurs in order to log a message to the console before
> automatically rebooting the machine.
>
> Signed-off-by: Chris Coulson <chris.coulson@canonical.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Daniel
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] kern/efi: Log a console error during a stack check failure
2022-03-22 17:05 ` Daniel Kiper
@ 2022-07-11 5:59 ` Glenn Washburn
0 siblings, 0 replies; 3+ messages in thread
From: Glenn Washburn @ 2022-07-11 5:59 UTC (permalink / raw)
To: Daniel Kiper; +Cc: The development of GNU GRUB, Chris Coulson
On Tue, 22 Mar 2022 18:05:29 +0100
Daniel Kiper <dkiper@net-space.pl> wrote:
> On Mon, Mar 21, 2022 at 03:14:39PM +0000, Chris Coulson wrote:
> > The initial implementation of the stack protector just busy looped
> > in __stack_chk_fail in order to reduce the amount of code being
> > executed after the stack has been compromised because of a lack of
> > firmware memory protections. With future firmware implementations
> > incorporating memory protections such as W^X, call in to boot services
> > when an error occurs in order to log a message to the console before
> > automatically rebooting the machine.
> >
> > Signed-off-by: Chris Coulson <chris.coulson@canonical.com>
>
> Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
I believe this is causing a build failure for arm64-efi with gcc 10.3.0, and
suspect this failure should occur on any gcc.
/builds/grub/grub-core/kern/efi/init.c:35:3: error: cannot initialize array of ‘short unsigned int’ from a string literal with type array of ‘unsigned int’
35 | L"* GRUB: STACK SMASHING DETECTED!!! *\r\n"
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
make[3]: *** [Makefile:36566: kern/efi/kernel_exec-init.o] Error 1
Glenn
^ permalink raw reply [flat|nested] 3+ messages in thread
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2022-03-21 15:14 [PATCH] kern/efi: Log a console error during a stack check failure Chris Coulson
2022-03-22 17:05 ` Daniel Kiper
2022-07-11 5:59 ` Glenn Washburn
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