Commit 65da3484 authored by NeilBrown's avatar NeilBrown Committed by Greg Kroah-Hartman

sysfs: correctly handle short reads on PREALLOC attrs.

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: default avatarNeilBrown <neilb@suse.com>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent cfcf6a91
...@@ -108,6 +108,7 @@ static ssize_t sysfs_kf_read(struct kernfs_open_file *of, char *buf, ...@@ -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); const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
struct kobject *kobj = of->kn->parent->priv; struct kobject *kobj = of->kn->parent->priv;
size_t len;
/* /*
* If buf != of->prealloc_buf, we don't know how * 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, ...@@ -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)) if (pos || WARN_ON_ONCE(buf != of->prealloc_buf))
return 0; 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 */ /* kernfs write callback for regular sysfs files */
......
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