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buffer: fix grow_buffers() for block size > PAGE_SIZE 

We must not shift by a negative number so work in terms of a byte offset
to avoid the awkward shift left-or-right-depending-on-sign option.  This
means we need to use check_mul_overflow() to ensure that a large block
number does not result in a wrap.

Link: https://lkml.kernel.org/r/20231109210608.2252323-4-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Pankaj Raghav <p.raghav@samsung.com>
Cc: Ryusuke Konishi <konishi.ryusuke@gmail.com>
[nathan@kernel.org: add cast in grow_buffers() to avoid a multiplication libcall]
  Link: https://lkml.kernel.org/r/20231128-avoid-muloti4-grow_buffers-v1-1-bc3d0f0ec483@kernel.org
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2023-11-09 21:06:04 +00:00 committed by Andrew Morton
parent 382497ada0
commit 5f3bd90d9b
1 changed files with 6 additions and 11 deletions
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17
fs/buffer.c
View File

@ -1085,26 +1085,21 @@ unlock:
static bool grow_buffers(struct block_device *bdev, sector_t block,
unsigned size, gfp_t gfp)
{
pgoff_t index;
int sizebits;
sizebits = PAGE_SHIFT - __ffs(size);
index = block >> sizebits;
loff_t pos;
/*
* Check for a block which wants to lie outside our maximum possible
* pagecache index. (this comparison is done using sector_t types).
* Check for a block which lies outside our maximum possible
* pagecache index.
*/
if (unlikely(index != block >> sizebits)) {
printk(KERN_ERR "%s: requested out-of-range block %llu for "
"device %pg\n",
if (check_mul_overflow(block, (sector_t)size, &pos) || pos > MAX_LFS_FILESIZE) {
printk(KERN_ERR "%s: requested out-of-range block %llu for device %pg\n",
__func__, (unsigned long long)block,
bdev);
return false;
}
/* Create a folio with the proper size buffers */
return grow_dev_folio(bdev, block, index, size, gfp);
return grow_dev_folio(bdev, block, pos / PAGE_SIZE, size, gfp);
}
static struct buffer_head *