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pipe: simplify round_pipe_size()

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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/[email protected]
Signed-off-by: Eric Biggers <[email protected]>
Acked-by: Kees Cook <[email protected]>
Acked-by: Joe Lawrence <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: "Luis R . Rodriguez" <[email protected]>
Cc: Michael Kerrisk <[email protected]>
Cc: Mikulas Patocka <[email protected]>
Cc: Willy Tarreau <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Eric Biggers 2018-02-06 15:42:05 -08:00 • committed by Linus Torvalds
commit c4fed5a91f
1 changed files with 3 additions and 11 deletions
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14
fs/pipe.c
View file

@ -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;
return PAGE_SIZE;
nr_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
if (nr_pages == 0)
return 0;
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)