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authorPavel Emelyanov <xemul@openvz.org>2008-04-29 04:02:40 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2008-04-29 11:06:23 -0400
commit7708bfb1c855f2a076ef71cc21647deea022ebe7 (patch)
tree9e4ba2b0074217b30a684eb9e77f6619434f4577 /fs/proc
parent1a46674b996bf9a15f0333178f5829ca2d7c32e2 (diff)
sysctl: merge equal proc_sys_read and proc_sys_write
Many (most of) sysctls do not have a per-container sense. E.g. kernel.print_fatal_signals, vm.panic_on_oom, net.core.netdev_budget and so on and so forth. Besides, tuning then from inside a container is not even secure. On the other hand, hiding them completely from the container's tasks sometimes causes user-space to stop working. When developing net sysctl, the common practice was to duplicate a table and drop the write bits in table->mode, but this approach was not very elegant, lead to excessive memory consumption and was not suitable in general. Here's the alternative solution. To facilitate the per-container sysctls ctl_table_root-s were introduced. Each root contains a list of ctl_table_header-s that are visible to different namespaces. The idea of this set is to add the permissions() callback on the ctl_table_root to allow ctl root limit permissions to the same ctl_table-s. The main user of this functionality is the net-namespaces code, but later this will (should) be used by more and more namespaces, containers and control groups. Actually, this idea's core is in a single hunk in the third patch. First two patches are cleanups for sysctl code, while the third one mostly extends the arguments set of some sysctl functions. This patch: These ->read and ->write callbacks act in a very similar way, so merge these paths to reduce the number of places to patch later and shrink the .text size (a bit). 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>
Diffstat (limited to 'fs/proc')
-rw-r--r--fs/proc/proc_sysctl.c50
1 files changed, 11 insertions, 39 deletions
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 614c34b6d1c2..5e31585292a0 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -165,8 +165,8 @@ out:
165 return err; 165 return err;
166} 166}
167 167
168static ssize_t proc_sys_read(struct file *filp, char __user *buf, 168static ssize_t proc_sys_call_handler(struct file *filp, void __user *buf,
169 size_t count, loff_t *ppos) 169 size_t count, loff_t *ppos, int write)
170{ 170{
171 struct dentry *dentry = filp->f_dentry; 171 struct dentry *dentry = filp->f_dentry;
172 struct ctl_table_header *head; 172 struct ctl_table_header *head;
@@ -190,12 +190,12 @@ static ssize_t proc_sys_read(struct file *filp, char __user *buf,
190 * and won't be until we finish. 190 * and won't be until we finish.
191 */ 191 */
192 error = -EPERM; 192 error = -EPERM;
193 if (sysctl_perm(table, MAY_READ)) 193 if (sysctl_perm(table, write ? MAY_WRITE : MAY_READ))
194 goto out; 194 goto out;
195 195
196 /* careful: calling conventions are nasty here */ 196 /* careful: calling conventions are nasty here */
197 res = count; 197 res = count;
198 error = table->proc_handler(table, 0, filp, buf, &res, ppos); 198 error = table->proc_handler(table, write, filp, buf, &res, ppos);
199 if (!error) 199 if (!error)
200 error = res; 200 error = res;
201out: 201out:
@@ -204,44 +204,16 @@ out:
204 return error; 204 return error;
205} 205}
206 206
207static ssize_t proc_sys_write(struct file *filp, const char __user *buf, 207static ssize_t proc_sys_read(struct file *filp, char __user *buf,
208 size_t count, loff_t *ppos) 208 size_t count, loff_t *ppos)
209{ 209{
210 struct dentry *dentry = filp->f_dentry; 210 return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 0);
211 struct ctl_table_header *head; 211}
212 struct ctl_table *table;
213 ssize_t error;
214 size_t res;
215
216 table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
217 /* Has the sysctl entry disappeared on us? */
218 error = -ENOENT;
219 if (!table)
220 goto out;
221
222 /* Has the sysctl entry been replaced by a directory? */
223 error = -EISDIR;
224 if (!table->proc_handler)
225 goto out;
226
227 /*
228 * At this point we know that the sysctl was not unregistered
229 * and won't be until we finish.
230 */
231 error = -EPERM;
232 if (sysctl_perm(table, MAY_WRITE))
233 goto out;
234
235 /* careful: calling conventions are nasty here */
236 res = count;
237 error = table->proc_handler(table, 1, filp, (char __user *)buf,
238 &res, ppos);
239 if (!error)
240 error = res;
241out:
242 sysctl_head_finish(head);
243 212
244 return error; 213static ssize_t proc_sys_write(struct file *filp, const char __user *buf,
214 size_t count, loff_t *ppos)
215{
216 return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 1);
245} 217}
246 218
247 219