| Message ID | 1471943977-17822-1-git-send-email-tomasz.majchrzak@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
[ adding Al ] On Tue, Aug 23, 2016 at 2:19 AM, Tomasz Majchrzak <tomasz.majchrzak@intel.com> wrote: > If kernfs file is empty on a first read, successive read operations > using the same file descriptor will return no data, even when data is > available. Default kernfs 'seq_next' implementation advances iterator > position even when next object is not there. Kernfs 'seq_start' for > following requests will not return iterator as position is already on > the second object. > > Don't set read position if valid iterator has not been returned. Can you say a bit about how you found this? So we have an idea about userspace tooling is broken by this bug. > > Signed-off-by: Tomasz Majchrzak <tomasz.majchrzak@intel.com> I would add "Cc: <stable@vger.kernel.org>" to the next version of this patch. > fs/seq_file.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/fs/seq_file.c b/fs/seq_file.c > index 19f532e..893db43 100644 > --- a/fs/seq_file.c > +++ b/fs/seq_file.c > @@ -242,7 +242,8 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos) > m->count = 0; > if (unlikely(!m->count)) { > p = m->op->next(m, p, &pos); > - m->index = pos; > + if (p && !IS_ERR(p)) Lets change this to use the IS_ERR_OR_NULL() helper, and do the same with the earlier if (!p || IS_ERR()) a few lines up in the loop. Other than that, this looks good to me. Reviewed-by: Dan Williams <dan.j.williams@intel.com> -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/seq_file.c b/fs/seq_file.c index 19f532e..893db43 100644 --- a/fs/seq_file.c +++ b/fs/seq_file.c @@ -242,7 +242,8 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos) m->count = 0; if (unlikely(!m->count)) { p = m->op->next(m, p, &pos); - m->index = pos; + if (p && !IS_ERR(p)) + m->index = pos; continue; } if (m->count < m->size)
If kernfs file is empty on a first read, successive read operations using the same file descriptor will return no data, even when data is available. Default kernfs 'seq_next' implementation advances iterator position even when next object is not there. Kernfs 'seq_start' for following requests will not return iterator as position is already on the second object. Don't set read position if valid iterator has not been returned. Signed-off-by: Tomasz Majchrzak <tomasz.majchrzak@intel.com> --- fs/seq_file.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)