From c4fed5a91fadc8a277b1eda474317b501651dd3e Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Tue, 6 Feb 2018 15:42:05 -0800 Subject: [PATCH] pipe: simplify round_pipe_size() 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. Link: http://lkml.kernel.org/r/20180111052902.14409-7-ebiggers3@gmail.com Signed-off-by: Eric Biggers Acked-by: Kees Cook Acked-by: Joe Lawrence Cc: Alexander Viro Cc: "Luis R . Rodriguez" Cc: Michael Kerrisk Cc: Mikulas Patocka Cc: Willy Tarreau Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/pipe.c | 14 +++----------- 1 file changed, 3 insertions(+), 11 deletions(-) diff --git a/fs/pipe.c b/fs/pipe.c index 817393d36244..8be52158c400 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) -- 2.30.2