sysfs: correctly handle short reads on PREALLOC attrs. (65da3484) · Commits · 戴 / test

attributes declared with __ATTR_PREALLOC use sysfs_kf_read() which ignores the 'count' arg. So a 1-byte read request can return more bytes than that. This is seen with the 'dash' shell when 'read' is used on some 'md' sysfs attributes. So only return the 'min' of count and the attribute length. Signed-off-by:

NeilBrown <neilb@suse.com> Acked-by:

Tejun Heo <tj@kernel.org> Signed-off-by:

Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/sysfs/file.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -108,6 +108,7 @@ static ssize_t sysfs_kf_read(struct kernfs_open_file of, char buf,
		{
		const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
		struct kobject *kobj = of->kn->parent->priv;
		size_t len;

		/*
		* If buf != of->prealloc_buf, we don't know how
		@@ -115,7 +116,8 @@ static ssize_t sysfs_kf_read(struct kernfs_open_file of, char buf,
		*/
		if (pos \|\| WARN_ON_ONCE(buf != of->prealloc_buf))
		return 0;
		return ops->show(kobj, of->kn->priv, buf);
		len = ops->show(kobj, of->kn->priv, buf);
		return min(count, len);
		}

		/* kernfs write callback for regular sysfs files */

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