lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20230912065500.886599632@linutronix.de>
Date:   Tue, 12 Sep 2023 09:57:46 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, Borislav Petkov <bp@...en8.de>,
        "Chang S. Bae" <chang.seok.bae@...el.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Nikolay Borisov <nik.borisov@...e.com>
Subject: [patch V3 02/30] x86/boot/32: Disable stackprotector and tracing for
 mk_early_pgtbl_32()

Stackprotector cannot work before paging is enabled. The read from the per
CPU variable __stack_chk_guard is always accessing the virtual address
either directly on UP or via FS on SMP. In physical address mode this
results in an access to memory above 3GB.

So this works by chance as the hardware returns the same value when there
is no RAM at this physical address. When there is RAM populated above 3G
then the read is by chance the same as nothing changes that memory during
the very early boot stage.

Stop relying on pure luck and disable the stack protector for the only C
function which is called during early boot before paging is enabled.

Remove function tracing from the whole source file as there is no way to
trace this at all, but in case of CONFIG_DYNAMIC_FTRACE=n
mk_early_pgtbl_32() would access global function tracer variables in
physcial address mode which again might work by chance.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/kernel/Makefile |    1 +
 arch/x86/kernel/head32.c |    3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -16,6 +16,7 @@ CFLAGS_REMOVE_kvmclock.o = -pg
 CFLAGS_REMOVE_ftrace.o = -pg
 CFLAGS_REMOVE_early_printk.o = -pg
 CFLAGS_REMOVE_head64.o = -pg
+CFLAGS_REMOVE_head32.o = -pg
 CFLAGS_REMOVE_sev.o = -pg
 CFLAGS_REMOVE_rethook.o = -pg
 endif
--- a/arch/x86/kernel/head32.c
+++ b/arch/x86/kernel/head32.c
@@ -73,7 +73,8 @@ asmlinkage __visible void __init __noret
  * always zero at this stage.
  */
 void __init mk_early_pgtbl_32(void);
-void __init mk_early_pgtbl_32(void)
+
+void __init __no_stack_protector mk_early_pgtbl_32(void)
 {
 #ifdef __pa
 #undef __pa

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ