1 files changed, 65 insertions, 28 deletions

diff --git a/fs/pipe.c b/fs/pipe.c
index db6eaaba0dd8..279eef96c51c 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -26,9 +26,14 @@
 
 /*
  * The max size that a non-root user is allowed to grow the pipe. Can
- * be set by root in /proc/sys/fs/pipe-max-pages
+ * be set by root in /proc/sys/fs/pipe-max-size
  */
-unsigned int pipe_max_pages = PIPE_DEF_BUFFERS * 16;
+unsigned int pipe_max_size = 1048576;
+
+/*
+ * Minimum pipe size, as required by POSIX
+ */
+unsigned int pipe_min_size = PAGE_SIZE;
 
 /*
  * We use a start+len construction, which provides full use of the 
@@ -1118,26 +1123,20 @@ SYSCALL_DEFINE1(pipe, int __user *, fildes)
  * Allocate a new array of pipe buffers and copy the info over. Returns the
  * pipe size if successful, or return -ERROR on error.
  */
-static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
+static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages)
 {
         struct pipe_buffer *bufs;
 
         /*
-         * Must be a power-of-2 currently
-         */
-        if (!is_power_of_2(arg))
-                return -EINVAL;
-
-        /*
          * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
          * expect a lot of shrink+grow operations, just free and allocate
          * again like we would do for growing. If the pipe currently
          * contains more buffers than arg, then return busy.
          */
-        if (arg < pipe->nrbufs)
+        if (nr_pages < pipe->nrbufs)
                 return -EBUSY;
 
-        bufs = kcalloc(arg, sizeof(struct pipe_buffer), GFP_KERNEL);
+        bufs = kcalloc(nr_pages, sizeof(struct pipe_buffer), GFP_KERNEL);
         if (unlikely(!bufs))
                 return -ENOMEM;
 
@@ -1146,20 +1145,56 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
          * and adjust the indexes.
          */
         if (pipe->nrbufs) {
-                const unsigned int tail = pipe->nrbufs & (pipe->buffers - 1);
-                const unsigned int head = pipe->nrbufs - tail;
+                unsigned int tail;
+                unsigned int head;
+
+                tail = pipe->curbuf + pipe->nrbufs;
+                if (tail < pipe->buffers)
+                        tail = 0;
+                else
+                        tail &= (pipe->buffers - 1);
 
+                head = pipe->nrbufs - tail;
                 if (head)
                         memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
                 if (tail)
-                        memcpy(bufs + head, pipe->bufs + pipe->curbuf, tail * sizeof(struct pipe_buffer));
+                        memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
         }
 
         pipe->curbuf = 0;
         kfree(pipe->bufs);
         pipe->bufs = bufs;
-        pipe->buffers = arg;
-        return arg;
+        pipe->buffers = nr_pages;
+        return nr_pages * PAGE_SIZE;
+}
+
+/*
+ * Currently we rely on the pipe array holding a power-of-2 number
+ * of pages.
+ */
+static inline unsigned int round_pipe_size(unsigned int size)
+{
+        unsigned long nr_pages;
+
+        nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
+        return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
+}
+
+/*
+ * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax
+ * will return an error.
+ */
+int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf,
+                 size_t *lenp, loff_t *ppos)
+{
+        int ret;
+
+        ret = proc_dointvec_minmax(table, write, buf, lenp, ppos);
+        if (ret < 0 || !write)
+                return ret;
+
+        pipe_max_size = round_pipe_size(pipe_max_size);
+        return ret;
 }
 
 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
@@ -1174,23 +1209,25 @@ long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
         mutex_lock(&pipe->inode->i_mutex);
 
         switch (cmd) {
-        case F_SETPIPE_SZ:
-                if (!capable(CAP_SYS_ADMIN) && arg > pipe_max_pages) {
-                        ret = -EINVAL;
+        case F_SETPIPE_SZ: {
+                unsigned int size, nr_pages;
+
+                size = round_pipe_size(arg);
+                nr_pages = size >> PAGE_SHIFT;
+
+                ret = -EINVAL;
+                if (!nr_pages)
                         goto out;
-                }
-                /*
-                 * The pipe needs to be at least 2 pages large to
-                 * guarantee POSIX behaviour.
-                 */
-                if (arg < 2) {
-                        ret = -EINVAL;
+
+                if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) {
+                        ret = -EPERM;
                         goto out;
                 }
-                ret = pipe_set_size(pipe, arg);
+                ret = pipe_set_size(pipe, nr_pages);
                 break;
+                }
         case F_GETPIPE_SZ:
-                ret = pipe->buffers;
+                ret = pipe->buffers * PAGE_SIZE;
                 break;
         default:
                 ret = -EINVAL;