pipe: fix pipe buffer resizing

[safe/jmp/linux-2.6] / fs / pipe.c

diff --git a/fs/pipe.c b/fs/pipe.c
index db6eaab..f31e2d4 100644 (file)
--- 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 +1209,24 @@ 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;
+
+               if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) {
+                       ret = -EPERM;
                        goto out;
-               }
-               /*
-                * The pipe needs to be at least 2 pages large to
-                * guarantee POSIX behaviour.
-                */
-               if (arg < 2) {
+               } else if (nr_pages < PAGE_SIZE) {
                        ret = -EINVAL;
                        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;