3.16.57-rc1 review patch. If anyone has any objections, please let me know.
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From: Eric Biggers ebiggers@google.com
commit c4fed5a91fadc8a277b1eda474317b501651dd3e upstream.
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 ebiggers@google.com Acked-by: Kees Cook keescook@chromium.org Acked-by: Joe Lawrence joe.lawrence@redhat.com Cc: Alexander Viro viro@zeniv.linux.org.uk Cc: "Luis R . Rodriguez" mcgrof@kernel.org Cc: Michael Kerrisk mtk.manpages@gmail.com Cc: Mikulas Patocka mpatocka@redhat.com Cc: Willy Tarreau w@1wt.eu Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Ben Hutchings ben@decadent.org.uk --- fs/pipe.c | 14 +++----------- 1 file changed, 3 insertions(+), 11 deletions(-)
--- a/fs/pipe.c +++ b/fs/pipe.c @@ -1010,20 +1010,14 @@ const struct file_operations pipefifo_fo */ 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); }
/* @@ -1038,8 +1032,6 @@ static long pipe_set_size(struct pipe_in long ret = 0;
size = round_pipe_size(arg); - if (size == 0) - return -EINVAL; nr_pages = size >> PAGE_SHIFT;
if (!nr_pages)