On Fri, 2018-03-16 at 01:00 +0800, Coly Li wrote: > On 15/03/2018 11:08 PM, Bart Van Assche wrote: > > copy_to_user() returns the number of remaining bytes. Avoid that > > a larger value is returned than the number of bytes that have > > been copied by returning -EFAULT if not all bytes have been copied. > > > > Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxx> > > --- > > drivers/md/bcache/debug.c | 5 ++--- > > 1 file changed, 2 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/md/bcache/debug.c b/drivers/md/bcache/debug.c > > index af89408befe8..376899cfcbf1 100644 > > --- a/drivers/md/bcache/debug.c > > +++ b/drivers/md/bcache/debug.c > > @@ -175,9 +175,8 @@ static ssize_t bch_dump_read(struct file *file, char __user *buf, > > struct keybuf_key *w; > > unsigned bytes = min(i->bytes, size); > > > > - int err = copy_to_user(buf, i->buf, bytes); > > - if (err) > > - return err; > > + if (copy_to_user(buf, i->buf, bytes)) > > + return -EFAULT; > > > > Hi Bart, > > I am not sure whether this change is correct. -EFAULT seems not an > expected return value of read(2), while -1 is the expected return value > when error occurs. > > Maybe if copy_to_user() returns value in (0, size], "ret + (size - err)" > should be returned. An exception is when copy_to_user() returns 0 and > ret is 0 too, in this situation -1 should be returned. > > Correct me if I am wrong. Hello Coly, I'm not familiar enough with bcache to provide the answer to your question so I will drop this patch from this series. Thanks, Bart.
