From: Eric Biggers <ebigg...@google.com>
round_pipe_size() calculates the number of pages the requested size
corresponds to, then rounds the page count up to the next power of 2.
However, it also rounds everything < PAGE_SIZE up to PAGE_SIZE.
Therefore, there's no need to actually translate the size into a page
count; we just need to round the size up to the next power of 2.
We do need to verify the size isn't greater than (1 << 31), since on
32-bit systems roundup_pow_of_two() would be undefined in that case.
But that can just be combined with the UINT_MAX check which we need
anyway now.
Finally, update pipe_set_size() to not redundantly check the return
value of round_pipe_size() for the "invalid size" case twice.
Signed-off-by: Eric Biggers <ebigg...@google.com>
---
fs/pipe.c | 14 +++-----------
1 file changed, 3 insertions(+), 11 deletions(-)
diff --git a/fs/pipe.c b/fs/pipe.c
index f1ee1e599495..458f866caf53 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -1022,20 +1022,14 @@ const struct file_operations pipefifo_fops = {
*/
unsigned int round_pipe_size(unsigned long size)
{
- unsigned long nr_pages;
-
- if (size > UINT_MAX)
+ if (size > (1U << 31))
return 0;
/* Minimum pipe size, as required by POSIX */
if (size < PAGE_SIZE)
- size = PAGE_SIZE;
-
- nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
- if (nr_pages == 0)
- return 0;
+ return PAGE_SIZE;
- return roundup_pow_of_two(nr_pages) << PAGE_SHIFT;
+ return roundup_pow_of_two(size);
}
/*
@@ -1050,8 +1044,6 @@ static long pipe_set_size(struct pipe_inode_info *pipe,
unsigned long arg)
long ret = 0;
size = round_pipe_size(arg);
- if (size == 0)
- return -EINVAL;
nr_pages = size >> PAGE_SHIFT;
if (!nr_pages)
--
2.15.1
