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SubjectRe: [PATCH -next 1/1] iomap: Fix a false positive of UBSAN in iomap_seek_data()
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On 2021/7/2 17:34, Christoph Hellwig wrote:
> We might as well just kill off the length variable while we're at it:

Hi, Christoph:
Maybe you need to write a separate patch. Because the patch I sent is
to modify function iomap_seek_data(). I didn't look at the other functions.
In fact, both iomap_seek_data() and iomap_seek_hole() need to be modified.
The iomap_seek_data() may not be intuitive to delete the variable 'length'.

I'm now analyzing if the "if (length <= 0)" statement in iomap_seek_data()
is redundant (the condition is never true).

>
>
> diff --git a/fs/iomap/seek.c b/fs/iomap/seek.c
> index dab1b02eba5b7f..942e354e9e13e6 100644
> --- a/fs/iomap/seek.c
> +++ b/fs/iomap/seek.c
> @@ -35,23 +35,21 @@ loff_t
> iomap_seek_hole(struct inode *inode, loff_t offset, const struct iomap_ops *ops)
> {
> loff_t size = i_size_read(inode);
> - loff_t length = size - offset;
> loff_t ret;
>
> /* Nothing to be found before or beyond the end of the file. */
> if (offset < 0 || offset >= size)
> return -ENXIO;
>
> - while (length > 0) {
> - ret = iomap_apply(inode, offset, length, IOMAP_REPORT, ops,
> - &offset, iomap_seek_hole_actor);
> + while (offset < size) {
> + ret = iomap_apply(inode, offset, size - offset, IOMAP_REPORT,
> + ops, &offset, iomap_seek_hole_actor);
> if (ret < 0)
> return ret;
> if (ret == 0)
> break;
>
> offset += ret;
> - length -= ret;
> }
>
> return offset;
>
> .
>

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