On Mon, Oct 05, 2026 at 07:54:11PM +0100, David Laight wrote: > On Mon, 5 Oct 2026 08:56:53 -0700 > Kees Cook <[email protected]> wrote: > > > lpfc_rx_monitor_report() formats each record into a stack buffer, then > > appends it with seq_buf_puts(), relying on seq_buf_puts() appending > > nothing when a string does not fit: the debugfs output then ends at the > > last whole record, and the record left out is read in full next time. > > The next patch makes seq_buf_puts() copy as much as fits instead, as > > seq_buf_printf() and strlcat() do. > > > > Print each record with seq_buf_printf(), and when it does not fit, end > > the string where the record began, since the reader takes the buffer up > > to its NUL. This also takes the DBG_LOG_STR_SZ buffer off the stack. > > > > Build tested ARCH=x86_64 with GCC 16.2.0, CONFIG_SCSI_LPFC=m and W=1. > > > > Assisted-by: LLM > > Signed-off-by: Kees Cook <[email protected]> > > --- > > drivers/scsi/lpfc/lpfc_sli.c | 45 +++++++++++++++++++++--------------- > > 1 file changed, 27 insertions(+), 18 deletions(-) > > > > diff --git a/drivers/scsi/lpfc/lpfc_sli.c b/drivers/scsi/lpfc/lpfc_sli.c > > index cfa4371169f1..a7b1ea67ed98 100644 > > --- a/drivers/scsi/lpfc/lpfc_sli.c > > +++ b/drivers/scsi/lpfc/lpfc_sli.c > > @@ -8108,7 +8108,6 @@ u32 lpfc_rx_monitor_report(struct lpfc_hba *phba, > > spinlock_t *ring_lock = &rx_monitor->lock; > > u32 ring_size = rx_monitor->entries; > > u32 cnt = 0; > > - char tmp[DBG_LOG_STR_SZ] = {0}; > > bool log_to_kmsg = (!buf || !buf_len) ? true : false; > > struct seq_buf s; > > > > @@ -8133,27 +8132,37 @@ u32 lpfc_rx_monitor_report(struct lpfc_hba *phba, > > > > /* Read out this entry's data. */ > > if (!log_to_kmsg) { > > + unsigned int len; > > + > > + /* A header that did not fit leaves no room. */ > > + if (seq_buf_has_overflowed(&s)) > > + break; > > + len = seq_buf_used(&s); > > + > > + seq_buf_printf(&s, > > + > > "%03d:\t%-16llu%-16llu%-16llu%-16llu%-8llu%-8llu%-8llu%-8u%-8u%-8u%u(%u)\n", > > + *head_idx, > > + entry->max_bytes_per_interval, > > + entry->cmf_bytes, > > + entry->total_bytes, > > + entry->rcv_bytes, > > + entry->avg_io_latency, > > + entry->avg_io_size, > > + entry->max_read_cnt, > > + entry->cmf_busy, entry->io_cnt, > > + entry->cmf_info, > > + entry->timer_utilization, > > + entry->timer_interval); > > + > > /* > > * Drop a record whole if it does not fit, without > > - * consuming its ring entry. > > + * consuming its ring entry: the reader takes the > > + * string up to its NUL. > > */ > > - scnprintf(tmp, sizeof(tmp), > > - > > "%03d:\t%-16llu%-16llu%-16llu%-16llu%-8llu%-8llu%-8llu%-8u%-8u%-8u%u(%u)\n", > > - *head_idx, > > - entry->max_bytes_per_interval, > > - entry->cmf_bytes, > > - entry->total_bytes, > > - entry->rcv_bytes, > > - entry->avg_io_latency, > > - entry->avg_io_size, > > - entry->max_read_cnt, > > - entry->cmf_busy, entry->io_cnt, > > - entry->cmf_info, > > - entry->timer_utilization, > > - entry->timer_interval); > > - > > - if (seq_buf_puts(&s, tmp) < 0) > > + if (seq_buf_has_overflowed(&s)) { > > + buf[len] = '\0'; > > There should probably be a seq_buf_truncate() to do that. > Then a request for the length will be correct.
We don't really have a "rewind" API. (Oh please don't make me add another API ... I'm at 3 already in this series...) -- Kees Cook
