[SCSI] libfc: fix memory corruption caused by double frees and bad error handling

I was running into several different panics under stress, which I traced down
to a few different possible slab corruption issues in error handling paths.
I have not yet looked into why these exchange sends fail, but with these
fixes my test system is much more stable under stress than before.

fc_elsct_send() could fail and either leave the passed in frame intact
(failure in fc_ct/els_fill) or the frame could have been freed if the
failure was is fc_exch_seq_send().  The caller had no way of knowing, and
there was a potential double free in the error handling in fc_fcp_rec().

Make fc_elsct_send() always free the frame before returning, and remove the
fc_frame_free() call in fc_fcp_rec().

While fc_exch_seq_send() did always consume the frame, there were double free
bugs in the error handling of fc_fcp_cmd_send() and fc_fcp_srr() as well.

Numerous calls to error handling routines (fc_disc_error(),
fc_lport_error(), fc_rport_error_retry() ) were passing in a frame pointer that
had already been freed in the case of an error.  I have changed the call
sites to pass in a NULL pointer, but there may be more appropriate error
codes to use.

Question:  Why do these error routines take a frame pointer anyway?  I
understand passing in a pointer encoded error to the response handlers, but
the error routines take no action on a valid pointer and should never be
called that way.

Signed-off-by: Chris Leech <christopher.leech@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

1 files changed, 2 insertions, 5 deletions

diff --git a/drivers/scsi/libfc/fc_fcp.c b/drivers/scsi/libfc/fc_fcp.c
index 28bfe1c2c50a..a67f53a5026c 100644
--- a/drivers/scsi/libfc/fc_fcp.c
+++ b/drivers/scsi/libfc/fc_fcp.c
@@ -1051,7 +1051,6 @@ static int fc_fcp_cmd_send(struct fc_lport *lp, struct fc_fcp_pkt *fsp,
 
         seq = lp->tt.exch_seq_send(lp, fp, resp, fc_fcp_pkt_destroy, fsp, 0);
         if (!seq) {
-                fc_frame_free(fp);
                 rc = -1;
                 goto unlock;
         }
@@ -1316,7 +1315,6 @@ static void fc_fcp_rec(struct fc_fcp_pkt *fsp)
                 fc_fcp_pkt_hold(fsp);           /* hold while REC outstanding */
                 return;
         }
-        fc_frame_free(fp);
 retry:
         if (fsp->recov_retry++ < FC_MAX_RECOV_RETRY)
                 fc_fcp_timer_set(fsp, FC_SCSI_REC_TOV);
@@ -1564,10 +1562,9 @@ static void fc_fcp_srr(struct fc_fcp_pkt *fsp, enum fc_rctl r_ctl, u32 offset)
 
         seq = lp->tt.exch_seq_send(lp, fp, fc_fcp_srr_resp, NULL,
                                    fsp, jiffies_to_msecs(FC_SCSI_REC_TOV));
-        if (!seq) {
-                fc_frame_free(fp);
+        if (!seq)
                 goto retry;
-        }
+
         fsp->recov_seq = seq;
         fsp->xfer_len = offset;
         fsp->xfer_contig_end = offset;