sysctl: add the ->permissions callback on the ctl_table_root

When reading from/writing to some table, a root, which this table came from,
may affect this table's permissions, depending on who is working with the
table.

The core hunk is at the bottom of this patch.  All the rest is just pushing
the ctl_table_root argument up to the sysctl_perm() function.

This will be mostly (only?) used in the net sysctls.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Acked-by: David S. Miller <davem@davemloft.net>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Alexey Dobriyan <adobriyan@sw.ru>
Cc: Denis V. Lunev <den@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 5e31585292a0e3f9be9a6f1b4703ef66fb6c9062..5acc001d49f6c72db83216173136701c2169f950 100644 (file)
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -190,7 +190,7 @@ static ssize_t proc_sys_call_handler(struct file *filp, void __user *buf,
         * and won't be until we finish.
         */
        error = -EPERM;
-       if (sysctl_perm(table, write ? MAY_WRITE : MAY_READ))
+       if (sysctl_perm(head->root, table, write ? MAY_WRITE : MAY_READ))
                goto out;
 
        /* careful: calling conventions are nasty here */
@@ -388,7 +388,7 @@ static int proc_sys_permission(struct inode *inode, int mask, struct nameidata *
                goto out;
 
        /* Use the permissions on the sysctl table entry */
-       error = sysctl_perm(table, mask);
+       error = sysctl_perm(head->root, table, mask);
 out:
        sysctl_head_finish(head);
        return error;

diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 39eafd8f97a3f54936a3b856006633f2dd340053..24141b4d1a116a4523ab9085e8f830cdd26cb471 100644 (file)
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -945,11 +945,14 @@ enum
 /* For the /proc/sys support */
 struct ctl_table;
 struct nsproxy;
+struct ctl_table_root;
+
 extern struct ctl_table_header *sysctl_head_next(struct ctl_table_header *prev);
 extern struct ctl_table_header *__sysctl_head_next(struct nsproxy *namespaces,
                                                struct ctl_table_header *prev);
 extern void sysctl_head_finish(struct ctl_table_header *prev);
-extern int sysctl_perm(struct ctl_table *table, int op);
+extern int sysctl_perm(struct ctl_table_root *root,
+               struct ctl_table *table, int op);
 
 typedef struct ctl_table ctl_table;
 
@@ -1049,6 +1052,8 @@ struct ctl_table_root {
        struct list_head header_list;
        struct list_head *(*lookup)(struct ctl_table_root *root,
                                           struct nsproxy *namespaces);
+       int (*permissions)(struct ctl_table_root *root,
+                       struct nsproxy *namespaces, struct ctl_table *table);
 };
 
 /* struct ctl_table_header is used to maintain dynamic lists of

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 874e813e40c8d33345d4bc8215a9da327294adec..d7ffdc59816ad3f822389d508f3c5ff1b030578d 100644 (file)
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1434,7 +1434,8 @@ void register_sysctl_root(struct ctl_table_root *root)
 
 #ifdef CONFIG_SYSCTL_SYSCALL
 /* Perform the actual read/write of a sysctl table entry. */
-static int do_sysctl_strategy(struct ctl_table *table,
+static int do_sysctl_strategy(struct ctl_table_root *root,
+                       struct ctl_table *table,
                        int __user *name, int nlen,
                        void __user *oldval, size_t __user *oldlenp,
                        void __user *newval, size_t newlen)
@@ -1445,7 +1446,7 @@ static int do_sysctl_strategy(struct ctl_table *table,
                op |= 004;
        if (newval)
                op |= 002;
-       if (sysctl_perm(table, op))
+       if (sysctl_perm(root, table, op))
                return -EPERM;
 
        if (table->strategy) {
@@ -1471,6 +1472,7 @@ static int do_sysctl_strategy(struct ctl_table *table,
 static int parse_table(int __user *name, int nlen,
                       void __user *oldval, size_t __user *oldlenp,
                       void __user *newval, size_t newlen,
+                      struct ctl_table_root *root,
                       struct ctl_table *table)
 {
        int n;
@@ -1485,14 +1487,14 @@ repeat:
                if (n == table->ctl_name) {
                        int error;
                        if (table->child) {
-                               if (sysctl_perm(table, 001))
+                               if (sysctl_perm(root, table, 001))
                                        return -EPERM;
                                name++;
                                nlen--;
                                table = table->child;
                                goto repeat;
                        }
-                       error = do_sysctl_strategy(table, name, nlen,
+                       error = do_sysctl_strategy(root, table, name, nlen,
                                                   oldval, oldlenp,
                                                   newval, newlen);
                        return error;
@@ -1518,7 +1520,8 @@ int do_sysctl(int __user *name, int nlen, void __user *oldval, size_t __user *ol
        for (head = sysctl_head_next(NULL); head;
                        head = sysctl_head_next(head)) {
                error = parse_table(name, nlen, oldval, oldlenp, 
-                                       newval, newlen, head->ctl_table);
+                                       newval, newlen,
+                                       head->root, head->ctl_table);
                if (error != -ENOTDIR) {
                        sysctl_head_finish(head);
                        break;
@@ -1564,13 +1567,21 @@ static int test_perm(int mode, int op)
        return -EACCES;
 }
 
-int sysctl_perm(struct ctl_table *table, int op)
+int sysctl_perm(struct ctl_table_root *root, struct ctl_table *table, int op)
 {
        int error;
+       int mode;
+
        error = security_sysctl(table, op);
        if (error)
                return error;
-       return test_perm(table->mode, op);
+
+       if (root->permissions)
+               mode = root->permissions(root, current->nsproxy, table);
+       else
+               mode = table->mode;
+
+       return test_perm(mode, op);
 }
 
 static void sysctl_set_parent(struct ctl_table *parent, struct ctl_table *table)