[src/netbsd-1-4]: src/sys/kern Pull-up patch requested by Luke Mewburn.

[perry <perry%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/2ed0be0ae780
branches:  netbsd-1-4
changeset: 471304:2ed0be0ae780
user:      perry <perry%NetBSD.org@localhost>
date:      Thu Jul 19 13:36:19 2001 +0000

description:
Pull-up patch requested by Luke Mewburn.

Original commit message:

        In check_exec(), don't bother checking P_TRACED along with
        MNT_NOSUID, just check MNT_NOSUID to clear the S{U,G}ID bits
        in the attributes for the vnode we're about to exec.

        We now check P_TRACED right before we would actually perform
        the s{u,g}id function in the exec code.

        This closes a race condition between exec of a setuid binary
        and ptrace(2).

diffstat:

 sys/kern/exec_script.c |  11 +++++++----
 sys/kern/kern_exec.c   |  20 ++++++++++++++------
 2 files changed, 21 insertions(+), 10 deletions(-)

diffs (81 lines):

diff -r b49bb0bcdfdd -r 2ed0be0ae780 sys/kern/exec_script.c
--- a/sys/kern/exec_script.c    Wed May 30 09:46:46 2001 +0000
+++ b/sys/kern/exec_script.c    Thu Jul 19 13:36:19 2001 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: exec_script.c,v 1.20.2.1 2000/02/01 23:11:20 he Exp $  */
+/*     $NetBSD: exec_script.c,v 1.20.2.2 2001/07/19 13:36:19 perry Exp $       */
 
 /*
  * Copyright (c) 1993, 1994, 1996 Christopher G. Demetriou
@@ -146,8 +146,9 @@
 check_shell:
 #ifdef SETUIDSCRIPTS
        /*
-        * MNT_NOSUID and STRC are already taken care of by check_exec,
-        * so we don't need to worry about them now or later.
+        * MNT_NOSUID has already taken care of by check_exec,
+        * so we don't need to worry about it now or later.  We
+        * will need to check P_TRACED later, however.
         */
        script_sbits = epp->ep_vap->va_mode & (S_ISUID | S_ISGID);
        if (script_sbits != 0) {
@@ -260,7 +261,9 @@
 #ifdef SETUIDSCRIPTS
                /*
                 * set thing up so that set-id scripts will be
-                * handled appropriately
+                * handled appropriately.  P_TRACED will be
+                * checked later when the shell is actually
+                * exec'd.
                 */
                epp->ep_vap->va_mode |= script_sbits;
                if (script_sbits & S_ISUID)
diff -r b49bb0bcdfdd -r 2ed0be0ae780 sys/kern/kern_exec.c
--- a/sys/kern/kern_exec.c      Wed May 30 09:46:46 2001 +0000
+++ b/sys/kern/kern_exec.c      Thu Jul 19 13:36:19 2001 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_exec.c,v 1.100.2.3 2000/02/01 22:55:07 he Exp $   */
+/*     $NetBSD: kern_exec.c,v 1.100.2.4 2001/07/19 13:36:19 perry Exp $        */
 
 /*-
  * Copyright (C) 1993, 1994, 1996 Christopher G. Demetriou
@@ -123,7 +123,7 @@
                error = EACCES;
                goto bad1;
        }
-       if ((vp->v_mount->mnt_flag & MNT_NOSUID) || (p->p_flag & P_TRACED))
+       if (vp->v_mount->mnt_flag & MNT_NOSUID)
                epp->ep_vap->va_mode &= ~(S_ISUID | S_ISGID);
 
        /* try to open it */
@@ -444,10 +444,19 @@
 
        /*
         * deal with set[ug]id.
-        * MNT_NOEXEC and P_TRACED have already been used to disable s[ug]id.
+        * MNT_NOSUID has already been used to disable s[ug]id.
         */
-       if (((attr.va_mode & S_ISUID) != 0 && p->p_ucred->cr_uid != attr.va_uid)
-        || ((attr.va_mode & S_ISGID) != 0 && p->p_ucred->cr_gid != attr.va_gid)){
+       if ((p->p_flag & P_TRACED) == 0 &&
+           (((attr.va_mode & S_ISUID) != 0 &&
+             p->p_ucred->cr_uid != attr.va_uid) ||
+            ((attr.va_mode & S_ISGID) != 0 &&
+             p->p_ucred->cr_gid != attr.va_gid))) {
+               /*
+                * Mark the process as SUGID before we do
+                * anything that might block.
+                */
+               p->p_flag |= P_SUGID;
+
                p->p_ucred = crcopy(cred);
 #ifdef KTRACE
                /*
@@ -461,7 +470,6 @@
                        p->p_ucred->cr_uid = attr.va_uid;
                if (attr.va_mode & S_ISGID)
                        p->p_ucred->cr_gid = attr.va_gid;
-               p->p_flag |= P_SUGID;
        } else
                p->p_flag &= ~P_SUGID;
        p->p_cred->p_svuid = p->p_ucred->cr_uid;