From 7708bfb1c855f2a076ef71cc21647deea022ebe7 Mon Sep 17 00:00:00 2001 From: Pavel Emelyanov Date: Tue, 29 Apr 2008 01:02:40 -0700 Subject: [PATCH] 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 Acked-by: "David S. Miller" Cc: "Eric W. Biederman" Cc: Alexey Dobriyan Cc: Denis V. Lunev Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/proc_sysctl.c | 50 +++++++++++--------------------------------------- 1 file changed, 11 insertions(+), 39 deletions(-) diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c index 614c34b..5e31585 100644 --- a/fs/proc/proc_sysctl.c +++ b/fs/proc/proc_sysctl.c @@ -165,8 +165,8 @@ out: return err; } -static ssize_t proc_sys_read(struct file *filp, char __user *buf, - size_t count, loff_t *ppos) +static ssize_t proc_sys_call_handler(struct file *filp, void __user *buf, + size_t count, loff_t *ppos, int write) { struct dentry *dentry = filp->f_dentry; struct ctl_table_header *head; @@ -190,12 +190,12 @@ static ssize_t proc_sys_read(struct file *filp, char __user *buf, * and won't be until we finish. */ error = -EPERM; - if (sysctl_perm(table, MAY_READ)) + if (sysctl_perm(table, write ? MAY_WRITE : MAY_READ)) goto out; /* careful: calling conventions are nasty here */ res = count; - error = table->proc_handler(table, 0, filp, buf, &res, ppos); + error = table->proc_handler(table, write, filp, buf, &res, ppos); if (!error) error = res; out: @@ -204,44 +204,16 @@ out: return error; } -static ssize_t proc_sys_write(struct file *filp, const char __user *buf, +static ssize_t proc_sys_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos) { - struct dentry *dentry = filp->f_dentry; - struct ctl_table_header *head; - struct ctl_table *table; - ssize_t error; - size_t res; - - table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head); - /* Has the sysctl entry disappeared on us? */ - error = -ENOENT; - if (!table) - goto out; - - /* Has the sysctl entry been replaced by a directory? */ - error = -EISDIR; - if (!table->proc_handler) - goto out; - - /* - * At this point we know that the sysctl was not unregistered - * and won't be until we finish. - */ - error = -EPERM; - if (sysctl_perm(table, MAY_WRITE)) - goto out; - - /* careful: calling conventions are nasty here */ - res = count; - error = table->proc_handler(table, 1, filp, (char __user *)buf, - &res, ppos); - if (!error) - error = res; -out: - sysctl_head_finish(head); + return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 0); +} - return error; +static ssize_t proc_sys_write(struct file *filp, const char __user *buf, + size_t count, loff_t *ppos) +{ + return proc_sys_call_handler(filp, (void __user *)buf, count, ppos, 1); } -- 2.7.4