Bump On Wed, Jun 22, 2016 at 9:42 PM, Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> wrote: > Attributes declared with __ATTR_PREALLOC use sysfs_kf_read() which returns > zero bytes for non-zero offset. This breaks script checkarray in mdadm tool > in debian where /bin/sh is 'dash' because its builtin 'read' reads only one > byte at a time. Script gets 'i' instead of 'idle' when reads current action > from /sys/block/$dev/md/sync_action and as a result does nothing. > > This patch adds trivial implementation of partial read: generate whole > string and move required part into buffer head. > > Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> > Fixes: 4ef67a8c95f3 ("sysfs/kernfs: make read requests on pre-alloc files use the buffer.") > Link: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=787950 > Cc: Stable <stable@xxxxxxxxxxxxxxx> # v3.19+ > --- > fs/sysfs/file.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c > index f35523d4fa3a..b803213d1307 100644 > --- a/fs/sysfs/file.c > +++ b/fs/sysfs/file.c > @@ -114,9 +114,15 @@ static ssize_t sysfs_kf_read(struct kernfs_open_file *of, char *buf, > * If buf != of->prealloc_buf, we don't know how > * large it is, so cannot safely pass it to ->show > */ > - if (pos || WARN_ON_ONCE(buf != of->prealloc_buf)) > + if (WARN_ON_ONCE(buf != of->prealloc_buf)) > return 0; > len = ops->show(kobj, of->kn->priv, buf); > + if (pos) { > + if (len <= pos) > + return 0; > + len -= pos; > + memmove(buf, buf + pos, len); > + } > return min(count, len); > } > > -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html