linux-kernel - [PATCH for 2.6.22] [3/3] x86_64: Ignore compat mode SYSCALL when IA32

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: <20070623002925.EED7414B35@wotan.suse.de>
Date:	Sat, 23 Jun 2007 02:29:25 +0200 (CEST)
From:	Andi Kleen <ak@...e.de>
To:	jbeulich@...ell.com, patches@...-64.org, torvalds@...l.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH for 2.6.22] [3/3] x86_64: Ignore compat mode SYSCALL when IA32_EMULATION is not defined


Previously a program could switch to a compat mode segment and then
execute SYSCALL and it would jump to an uninitialized MSR and crash
the kernel.

Instead supply a dummy target for this case.

Pointed out by Jan Beulich

Cc: jbeulich@...ell.com
Signed-off-by: Andi Kleen <ak@...e.de>

---
 arch/x86_64/kernel/entry.S   |    7 +++++++
 arch/x86_64/kernel/setup64.c |    3 +++
 2 files changed, 10 insertions(+)

Index: linux/arch/x86_64/kernel/entry.S
===================================================================
--- linux.orig/arch/x86_64/kernel/entry.S
+++ linux/arch/x86_64/kernel/entry.S
@@ -1163,3 +1163,10 @@ ENTRY(call_softirq)
 	ret
 	CFI_ENDPROC
 ENDPROC(call_softirq)
+
+KPROBE_ENTRY(ignore_sysret)
+	CFI_STARTPROC
+	mov $-ENOSYS,%eax
+	sysret
+	CFI_ENDPROC
+ENDPROC(ignore_sysret)
Index: linux/arch/x86_64/kernel/setup64.c
===================================================================
--- linux.orig/arch/x86_64/kernel/setup64.c
+++ linux/arch/x86_64/kernel/setup64.c
@@ -150,6 +150,8 @@ void pda_init(int cpu)
 char boot_exception_stacks[(N_EXCEPTION_STACKS - 1) * EXCEPTION_STKSZ + DEBUG_STKSZ]
 __attribute__((section(".bss.page_aligned")));
 
+extern asmlinkage void ignore_sysret(void);
+
 /* May not be marked __init: used by software suspend */
 void syscall_init(void)
 {
@@ -160,6 +162,7 @@ void syscall_init(void)
 	 */ 
 	wrmsrl(MSR_STAR,  ((u64)__USER32_CS)<<48  | ((u64)__KERNEL_CS)<<32); 
 	wrmsrl(MSR_LSTAR, system_call); 
+	wrmsrl(MSR_CSTAR, ignore_sysret);
 
 #ifdef CONFIG_IA32_EMULATION   		
 	syscall32_cpu_init ();
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/