发布日期：2001-05-30
更新日期：2001-06-06

受影响系统：

NetBSD NetBSD 1.5 sh3
NetBSD NetBSD 1.4.1 sh3

描述：

---

BUGTRAQ  ID: 2810
CVE(CAN) ID: CAN-2001-0734

sh3平台上的NetBSD系统存在漏洞，它对用户提供的一个系统调用参数缺少适当的
检查，本地用户利用这个漏洞能以超级用户权限执行任意代码。

问题在于"sigreturn"系统调用和"process_write_regs"内核子程序对用户提供的
"Status Register"内容没做适当的检查造成的。

<*来源：Klaus Klein
       NetBSD Security Advisory 2001-008
*>

建议：

---

正在运行2001/5/16以前版本的NetBSD-current用户应该升级到这个日期以后的版本。

正在运行2001/5/27以前版本的NetBSD-release 1.5用户应该升级到这个日期以后的版本。

NetBSD也提供了补丁程序：

Index: include/psl.h
===================================================================
RCS file: /cvsroot/syssrc/sys/arch/sh3/include/psl.h,v
retrieving revision 1.1
retrieving revision 1.2
diff -u -r1.1 -r1.2
- --- include/psl.h    1999/09/13 10:31:21    1.1
+++ include/psl.h    2001/05/16 12:42:38    1.2
@@ -57,8 +57,8 @@
#define    PSL_MBO        0x00000000    /* must be one bits */
#define    PSL_MBZ        0x8ffffc0c    /* must be zero bits */

- -#define PSL_USERSET    0
- -#define PSL_USERSTATIC    (PSL_BL|PSL_RB|PSL_MD|PSL_IMASK)
+#define PSL_USERSET    0
+#define PSL_USERSTATIC    (PSL_BL|PSL_RB|PSL_MD|PSL_IMASK|PSL_MBO|PSL_MBZ)

#ifdef _KERNEL
#include <machine/intr.h>
Index: sh3/compat_13_machdep.c
===================================================================
RCS file: /cvsroot/syssrc/sys/arch/sh3/sh3/compat_13_machdep.c,v
retrieving revision 1.2
retrieving revision 1.3
diff -u -r1.2 -r1.3
- --- sh3/compat_13_machdep.c    2000/12/22 22:58:55    1.2
+++ sh3/compat_13_machdep.c    2001/05/16 12:42:38    1.3
@@ -71,16 +71,9 @@
     /* Restore register context. */
     tf = p->p_md.md_regs;

- -    /*
- -     * Check for security violations.  If we're returning to
- -     * protected mode, the CPU will validate the segment registers
- -     * automatically and generate a trap on violations.  We handle
- -     * the trap, rather than doing all of the checking here.
- -     */
- -#ifdef TODO
+    /* Check for security violations.  */
     if (((context.sc_ssr ^ tf->tf_ssr) & PSL_USERSTATIC) != 0)
         return (EINVAL);
- -#endif

     tf->tf_ssr = context.sc_ssr;

Index: sh3/sh3_machdep.c
===================================================================
RCS file: /cvsroot/syssrc/sys/arch/sh3/sh3/sh3_machdep.c,v
retrieving revision 1.12
retrieving revision 1.13
diff -u -r1.12 -r1.13
- --- sh3/sh3_machdep.c    2001/04/24 04:31:09    1.12
+++ sh3/sh3_machdep.c    2001/05/16 12:42:38    1.13
@@ -350,21 +350,13 @@

     /* Restore signal context. */
     tf = p->p_md.md_regs;
- -    {
- -        /*
- -         * Check for security violations.  If we're returning to
- -         * protected mode, the CPU will validate the segment registers
- -         * automatically and generate a trap on violations.  We handle
- -         * the trap, rather than doing all of the checking here.
- -         */
- -#ifdef TODO
- -      if (((context.sc_ssr ^ tf->tf_ssr) & PSL_USERSTATIC) != 0) {
- -        return (EINVAL);
- -      }
- -#endif

- -      tf->tf_ssr = context.sc_ssr;
- -    }
+    /* Check for security violations. */
+    if (((context.sc_ssr ^ tf->tf_ssr) & PSL_USERSTATIC) != 0)
+        return (EINVAL);
+
+    tf->tf_ssr = context.sc_ssr;
+
     tf->tf_r0 = context.sc_r0;
     tf->tf_r1 = context.sc_r1;
     tf->tf_r2 = context.sc_r2;



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