pipe, sysctl: remove pipe_proc_fn()

pipe_proc_fn() is no longer needed, as it only calls through to
proc_dopipe_max_size().  Just put proc_dopipe_max_size() in the ctl_table
entry directly, and remove the unneeded EXPORT_SYMBOL() and the ENOSYS
stub for it.

(The reason the ENOSYS stub isn't needed is that the pipe-max-size
ctl_table entry is located directly in 'kern_table' rather than being
registered separately.  Therefore, the entry is already only defined when
the kernel is built with sysctl support.)

Link: http://lkml.kernel.org/r/20180111052902.14409-3-ebiggers3@gmail.com
Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "Luis R . Rodriguez" <mcgrof@kernel.org>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Willy Tarreau <w@1wt.eu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/pipe.c

@@ -1120,16 +1120,6 @@ out_revert_acct:
 	return ret;
 }
 
-/*
- * This should work even if CONFIG_PROC_FS isn't set, as proc_dopipe_max_size
- * will return an error.
- */
-int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
-		 size_t *lenp, loff_t *ppos)
-{
-	return proc_dopipe_max_size(table, write, buf, lenp, ppos);
-}
-
 /*
  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
  * location, so checking ->i_pipe is not enough to verify that this is a

include/linux/pipe_fs_i.h

@@ -170,7 +170,6 @@ void pipe_double_lock(struct pipe_inode_info *, struct pipe_inode_info *);
 extern unsigned int pipe_max_size;
 extern unsigned long pipe_user_pages_hard;
 extern unsigned long pipe_user_pages_soft;
-int pipe_proc_fn(struct ctl_table *, int, void __user *, size_t *, loff_t *);
 
 /* Drop the inode semaphore and wait for a pipe event, atomically */
 void pipe_wait(struct pipe_inode_info *pipe);

include/linux/sysctl.h

@@ -51,9 +51,6 @@ extern int proc_dointvec_minmax(struct ctl_table *, int,
 extern int proc_douintvec_minmax(struct ctl_table *table, int write,
 				 void __user *buffer, size_t *lenp,
 				 loff_t *ppos);
-extern int proc_dopipe_max_size(struct ctl_table *table, int write,
-				void __user *buffer, size_t *lenp,
-				loff_t *ppos);
 extern int proc_dointvec_jiffies(struct ctl_table *, int,
 				 void __user *, size_t *, loff_t *);
 extern int proc_dointvec_userhz_jiffies(struct ctl_table *, int,

kernel/sysctl.c

@@ -218,6 +218,8 @@ static int proc_dointvec_minmax_coredump(struct ctl_table *table, int write,
 static int proc_dostring_coredump(struct ctl_table *table, int write,
 		void __user *buffer, size_t *lenp, loff_t *ppos);
 #endif
+static int proc_dopipe_max_size(struct ctl_table *table, int write,
+		void __user *buffer, size_t *lenp, loff_t *ppos);
 
 #ifdef CONFIG_MAGIC_SYSRQ
 /* Note: sysrq code uses it's own private copy */
@@ -1812,7 +1814,7 @@ static struct ctl_table fs_table[] = {
 		.data		= &pipe_max_size,
 		.maxlen		= sizeof(pipe_max_size),
 		.mode		= 0644,
-		.proc_handler	= &pipe_proc_fn,
+		.proc_handler	= proc_dopipe_max_size,
 	},
 	{
 		.procname	= "pipe-user-pages-hard",
@@ -2637,8 +2639,8 @@ static int do_proc_dopipe_max_size_conv(unsigned long *lvalp,
 	return 0;
 }
 
-int proc_dopipe_max_size(struct ctl_table *table, int write,
-			 void __user *buffer, size_t *lenp, loff_t *ppos)
+static int proc_dopipe_max_size(struct ctl_table *table, int write,
+				void __user *buffer, size_t *lenp, loff_t *ppos)
 {
 	return do_proc_douintvec(table, write, buffer, lenp, ppos,
 				 do_proc_dopipe_max_size_conv, NULL);
@@ -3147,12 +3149,6 @@ int proc_douintvec_minmax(struct ctl_table *table, int write,
 	return -ENOSYS;
 }
 
-int proc_dopipe_max_size(struct ctl_table *table, int write,
-			 void __user *buffer, size_t *lenp, loff_t *ppos)
-{
-	return -ENOSYS;
-}
-
 int proc_dointvec_jiffies(struct ctl_table *table, int write,
 		    void __user *buffer, size_t *lenp, loff_t *ppos)
 {
@@ -3196,7 +3192,6 @@ EXPORT_SYMBOL(proc_douintvec);
 EXPORT_SYMBOL(proc_dointvec_jiffies);
 EXPORT_SYMBOL(proc_dointvec_minmax);
 EXPORT_SYMBOL_GPL(proc_douintvec_minmax);
-EXPORT_SYMBOL_GPL(proc_dopipe_max_size);
 EXPORT_SYMBOL(proc_dointvec_userhz_jiffies);
 EXPORT_SYMBOL(proc_dointvec_ms_jiffies);
 EXPORT_SYMBOL(proc_dostring);