pipe: fix pipe buffer resizing

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

diff --git a/fs/pipe.c b/fs/pipe.c
index 369a024..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 
@@ -1140,13 +1145,20 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages)
         * 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;
@@ -1156,6 +1168,35 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long 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)
 {
        struct pipe_inode_info *pipe;
@@ -1169,23 +1210,19 @@ long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
 
        switch (cmd) {
        case F_SETPIPE_SZ: {
-               unsigned long nr_pages;
+               unsigned int size, nr_pages;
 
-               /*
-                * Currently the array must be a power-of-2 size, so adjust
-                * upwards if needed.
-                */
-               nr_pages = (arg + PAGE_SIZE - 1) >> PAGE_SHIFT;
-               nr_pages = roundup_pow_of_two(nr_pages);
+               size = round_pipe_size(arg);
+               nr_pages = size >> PAGE_SHIFT;
 
-               if (!capable(CAP_SYS_ADMIN) && nr_pages > pipe_max_pages) {
+               if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) {
                        ret = -EPERM;
                        goto out;
-               } else if (nr_pages < 1) {
+               } 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: