Don't register empty sysctl dirs in /proc/sys.

They would be removed after registering some other sysctl(s) in the
same directory (e.g. rtc in /proc/sys/dev) and unregistering all of
them (then initially empty e.g. /proc/sys/dev disappears).
After disappearing of directory topdir ->de (for "dev") points to
structure which has been freed.
It's harmless in vanilla 2.4, but with grsecurity causes an Oops
on numeric sysctls referring to removed directory (even with all
grsecurity features disabled, only patch applied).

The same issue seems to exist in 2.6, and _probably_ can cause similar
problems in selinux.

Changed files:
    linux-2.4-sysctl-empty.patch -> 1.1

diff --git a/linux-2.4-sysctl-empty.patch b/linux-2.4-sysctl-empty.patch
new file mode 100644 (file)
index 0000000..27c8b49
--- /dev/null
+++ b/linux-2.4-sysctl-empty.patch
@@ -0,0 +1,61 @@
+Don't register empty sysctl dirs in /proc/sys.
+They would be removed after registering some other sysctl(s) in the
+same directory (e.g. rtc in /proc/sys/dev) and unregistering all of
+them (then initially empty e.g. /proc/sys/dev disappears).
+After disappearing of directory topdir ->de (for "dev") points to
+structure which has been freed.
+It's harmless in vanilla 2.4, but with grsecurity causes an Oops
+on numeric sysctls referring to removed directory (even with all
+grsecurity features disabled, only patch applied).
+
+The same issue seems to exist in 2.6, and _probably_ can cause similar
+problems in selinux.
+
+       -- Jakub Bogusz <qboosh@pld-linux.org>
+
+--- linux-2.4.20/kernel/sysctl.c.orig  Mon Dec 15 11:05:08 2003
++++ linux-2.4.20/kernel/sysctl.c       Mon Dec 15 15:48:46 2003
+@@ -124,10 +124,8 @@
+ #ifdef CONFIG_NET
+ extern ctl_table net_table[];
+ #endif
+-static ctl_table proc_table[];
+ static ctl_table fs_table[];
+ static ctl_table debug_table[];
+-static ctl_table dev_table[];
+ extern ctl_table random_table[];
+ 
+ static ctl_table grsecurity_table[];
+@@ -163,10 +161,8 @@
+ #ifdef CONFIG_NET
+       {CTL_NET, "net", NULL, 0, 0555, net_table},
+ #endif
+-      {CTL_PROC, "proc", NULL, 0, 0555, proc_table},
+       {CTL_FS, "fs", NULL, 0, 0555, fs_table},
+       {CTL_DEBUG, "debug", NULL, 0, 0555, debug_table},
+-        {CTL_DEV, "dev", NULL, 0, 0555, dev_table},
+       {0}
+ };
+ 
+@@ -488,10 +484,6 @@
+       {0}
+ };
+ 
+-static ctl_table proc_table[] = {
+-      {0}
+-};
+-
+ static ctl_table fs_table[] = {
+       {FS_NRINODE, "inode-nr", &inodes_stat, 2*sizeof(int),
+        0444, NULL, &proc_dointvec},
+@@ -526,10 +518,6 @@
+       {0}
+ };
+ 
+-static ctl_table dev_table[] = {
+-      {0}
+-};  
+-
+ extern void init_irq_proc (void);
+ 
+ void __init sysctl_init(void)