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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>
This commit is contained in:
Pavel Emelyanov 2008-04-29 01:02:44 -07:00 committed by Linus Torvalds
parent 2c4c7155f2
commit d7321cd624
3 changed files with 26 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
fs/proc/proc_sysctl.c
View File

@ -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;

7
include/linux/sysctl.h
View File

@ -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

25
kernel/sysctl.c
View File

@ -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)