From: Eric Biggers <[email protected]> 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 that bit 31 isn't set, 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, also remove the check for '!nr_pages' in pipe_set_size(), since round_pipe_size() always returns either 0 or a multiple of PAGE_SIZE. Signed-off-by: Eric Biggers <[email protected]> --- fs/pipe.c | 15 +++------------ 1 file changed, 3 insertions(+), 12 deletions(-) diff --git a/fs/pipe.c b/fs/pipe.c index f1ee1e599495..774cafd947dc 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); } /* @@ -1054,9 +1048,6 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg) return -EINVAL; nr_pages = size >> PAGE_SHIFT; - if (!nr_pages) - return -EINVAL; - /* * If trying to increase the pipe capacity, check that an * unprivileged user is not trying to exceed various limits -- 2.15.1
