From: Matthew Wilcox <willy@infradead.org>
To: "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
Cc: Ira Weiny <ira.weiny@intel.com>,
Viacheslav Dubeyko <slava@dubeyko.com>,
Andrew Morton <akpm@linux-foundation.org>,
Bart Van Assche <bvanassche@acm.org>,
Kees Cook <keescook@chromium.org>,
linux-fsdevel@vger.kernel.org
Subject: Re: kmap + memmove
Date: Mon, 6 May 2024 05:14:21 +0100 [thread overview]
Message-ID: <ZjhZHQShGq_LDyDe@casper.infradead.org> (raw)
In-Reply-To: <Zjd61vTCQoDN9tUJ@casper.infradead.org>
On Sun, May 05, 2024 at 01:25:58PM +0100, Matthew Wilcox wrote:
> Here's a fun bug that's not obvious:
>
> hfs_bnode_move:
> dst_ptr = kmap_local_page(*dst_page);
> src_ptr = kmap_local_page(*src_page);
> memmove(dst_ptr, src_ptr, src);
OK, so now we know this is the only place with this problem, how are we
going to fix it?
I think the obvious thing to do is to revert the kmap -> kmap_local
conversion in this function. The other functions look fine.
Longer term, hfs_bnode_move() makes my eyes bleed. I really think we
need to do something stupider. Something like ...
void hfs_bnode_move(struct hfs_bnode *node, int dst, int src, int len)
{
void *data;
int first, last;
if (!len || src == dst)
return;
if (src < dst && src + len < dst)
return hfs_bnode_copy(node, dst, node, src, len);
if (dst < src && dst + len < src)
return hfs_bnode_copy(node, dst, node, src, len);
src += node->page_offset;
dst += node->page_offset;
first = min(dst, src) / PAGE_SIZE;
last = max(dst + len, src + len) / PAGE_SIZE;
data = vmap_folios(bnode->folios + first, last - first + 1);
src -= first * PAGE_SIZE;
dst -= first * PAGE_SIZE;
// maybe an off-by-one in above calculations; check it
memmove(data + dst, data + src, len);
vunmap(data);
}
next prev parent reply other threads:[~2024-05-06 4:14 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-05 12:25 kmap + memmove Matthew Wilcox
2024-05-05 13:01 ` Julia Lawall
2024-05-06 3:40 ` Ira Weiny
2024-05-06 5:15 ` Julia Lawall
2024-05-06 5:48 ` Julia Lawall
2024-05-06 5:50 ` Julia Lawall
2024-05-06 3:47 ` Matthew Wilcox
2024-05-06 4:14 ` Matthew Wilcox [this message]
2024-05-24 19:35 ` Matthew Wilcox
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