[PATCH 16/20] libfc: fix memory corruption caused by double frees and bad error handling

Robert Love
2009-10-21T23:28:04Z

From: Chris Leech <christopher.leech@intel.com>

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>
---

drivers/scsi/libfc/fc_disc.c | 2 +-
drivers/scsi/libfc/fc_elsct.c | 4 +++-
drivers/scsi/libfc/fc_fcp.c | 7 ++-----
drivers/scsi/libfc/fc_lport.c | 8 ++++----
drivers/scsi/libfc/fc_rport.c | 10 +++++-----
5 files changed, 15 insertions(+), 16 deletions(-)

diff --git a/drivers/scsi/libfc/fc_disc.c b/drivers/scsi/libfc/fc_disc.c
index c48799e..d4cb3f9 100644
--- a/drivers/scsi/libfc/fc_disc.c
+++ b/drivers/scsi/libfc/fc_disc.c
@@ -371,7 +371,7 @@ static void fc_disc_gpn_ft_req(struct fc_disc *disc)
disc, lport->e_d_tov))
return;
err:
- fc_disc_error(disc, fp);
+ fc_disc_error(disc, NULL);
}

/**
diff --git a/drivers/scsi/libfc/fc_elsct.c b/drivers/scsi/libfc/fc_elsct.c
index 5cfa687..9298458 100644
--- a/drivers/scsi/libfc/fc_elsct.c
+++ b/drivers/scsi/libfc/fc_elsct.c
@@ -53,8 +53,10 @@ static struct fc_seq *fc_elsct_send(struct fc_lport *lport,
did = FC_FID_DIR_SERV;
}

- if (rc)
+ if (rc) {
+ fc_frame_free(fp);
return NULL;
+ }

fc_fill_fc_hdr(fp, r_ctl, did, fc_host_port_id(lport->host), fh_type,
FC_FC_FIRST_SEQ | FC_FC_END_SEQ | FC_FC_SEQ_INIT, 0);
diff --git a/drivers/scsi/libfc/fc_fcp.c b/drivers/scsi/libfc/fc_fcp.c
index 28bfe1c..a67f53a 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;
diff --git a/drivers/scsi/libfc/fc_lport.c b/drivers/scsi/libfc/fc_lport.c
index 0d19ffa..536492a 100644
--- a/drivers/scsi/libfc/fc_lport.c
+++ b/drivers/scsi/libfc/fc_lport.c
@@ -1115,7 +1115,7 @@ static void fc_lport_enter_scr(struct fc_lport *lport)

if (!lport->tt.elsct_send(lport, FC_FID_FCTRL, fp, ELS_SCR,
fc_lport_scr_resp, lport, lport->e_d_tov))
- fc_lport_error(lport, fp);
+ fc_lport_error(lport, NULL);
}

/**
@@ -1186,7 +1186,7 @@ static void fc_lport_enter_rpn_id(struct fc_lport *lport)
if (!lport->tt.elsct_send(lport, FC_FID_DIR_SERV, fp, FC_NS_RPN_ID,
fc_lport_rpn_id_resp,
lport, lport->e_d_tov))
- fc_lport_error(lport, fp);
+ fc_lport_error(lport, NULL);
}

static struct fc_rport_operations fc_lport_rport_ops = {
@@ -1340,7 +1340,7 @@ static void fc_lport_enter_logo(struct fc_lport *lport)

if (!lport->tt.elsct_send(lport, FC_FID_FLOGI, fp, ELS_LOGO,
fc_lport_logo_resp, lport, lport->e_d_tov))
- fc_lport_error(lport, fp);
+ fc_lport_error(lport, NULL);
}

/**
@@ -1456,7 +1456,7 @@ void fc_lport_enter_flogi(struct fc_lport *lport)

if (!lport->tt.elsct_send(lport, FC_FID_FLOGI, fp, ELS_FLOGI,
fc_lport_flogi_resp, lport, lport->e_d_tov))
- fc_lport_error(lport, fp);
+ fc_lport_error(lport, NULL);
}

/* Configure a fc_lport */
diff --git a/drivers/scsi/libfc/fc_rport.c b/drivers/scsi/libfc/fc_rport.c
index 1f795e4..49abb83 100644
--- a/drivers/scsi/libfc/fc_rport.c
+++ b/drivers/scsi/libfc/fc_rport.c
@@ -632,7 +632,7 @@ static void fc_rport_enter_plogi(struct fc_rport_priv *rdata)

if (!lport->tt.elsct_send(lport, rdata->ids.port_id, fp, ELS_PLOGI,
fc_rport_plogi_resp, rdata, lport->e_d_tov))
- fc_rport_error_retry(rdata, fp);
+ fc_rport_error_retry(rdata, NULL);
else
kref_get(&rdata->kref);
}
@@ -793,7 +793,7 @@ static void fc_rport_enter_prli(struct fc_rport_priv *rdata)

if (!lport->tt.elsct_send(lport, rdata->ids.port_id, fp, ELS_PRLI,
fc_rport_prli_resp, rdata, lport->e_d_tov))
- fc_rport_error_retry(rdata, fp);
+ fc_rport_error_retry(rdata, NULL);
else
kref_get(&rdata->kref);
}
@@ -889,7 +889,7 @@ static void fc_rport_enter_rtv(struct fc_rport_priv *rdata)

if (!lport->tt.elsct_send(lport, rdata->ids.port_id, fp, ELS_RTV,
fc_rport_rtv_resp, rdata, lport->e_d_tov))
- fc_rport_error_retry(rdata, fp);
+ fc_rport_error_retry(rdata, NULL);
else
kref_get(&rdata->kref);
}
@@ -919,7 +919,7 @@ static void fc_rport_enter_logo(struct fc_rport_priv *rdata)

if (!lport->tt.elsct_send(lport, rdata->ids.port_id, fp, ELS_LOGO,
fc_rport_logo_resp, rdata, lport->e_d_tov))
- fc_rport_error_retry(rdata, fp);
+ fc_rport_error_retry(rdata, NULL);
else
kref_get(&rdata->kref);
}
@@ -1006,7 +1006,7 @@ static void fc_rport_enter_adisc(struct fc_rport_priv *rdata)
}
if (!lport->tt.elsct_send(lport, rdata->ids.port_id, fp, ELS_ADISC,
fc_rport_adisc_resp, rdata, lport->e_d_tov))
- fc_rport_error_retry(rdata, fp);
+ fc_rport_error_retry(rdata, NULL);
else
kref_get(&rdata->kref);
}