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Wed, 11 Nov 2026 08:33:20 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id vhiNFFAo9Gp0GgAAD6G6ig (envelope-from ); Wed, 11 Nov 2026 08:33:20 +0000 Message-ID: Date: Wed, 11 Nov 2026 09:33:19 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] scsi: lpfc: Fix race conditions in ELS retry handling To: Kyle Mahlkuch , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, mkp@kernel.org Cc: Paul Ely , msmurthy@linux.ibm.com References: Content-Language: en-US From: Hannes Reinecke In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spamd-Result: default: False [-13.27 / 50.00]; SUSE_INTERNAL_BYPASS(-9.00)[]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-0.98)[-0.985]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; XM_UA_NO_VERSION(0.01)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; MIME_TRACE(0.00)[0:+]; TO_DN_SOME(0.00)[]; ARC_NA(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_FIVE(0.00)[6]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email,imap1.dmz-prg2.suse.org:helo] X-Spam-Score: -13.27 X-Spam-Level: X-Spam-Flag: NO On 11/10/26 9:16 PM, Kyle Mahlkuch wrote: > This patch addresses a race condition in the lpfc driver's ELS retry > event handling that can lead to a use-after-free in the > lpfc_cancel_retry_delay_tmo(), where the NLP_DELAY_TMO flag is cleared > before acquiring the lock to check if the retry event is queued. This > creates a window where the timer can be rescheduled and fire, causing > both the cancel path and the worker thread to release the same reference, > resulting in a double-put and use-after-free. > > Moved capture ndlp and clear evt_arg1 under hbalock while dequeuing > LPFC_EVT_ELS_RETRY in lpfc_work_list_done(). > > Signed-off-by: Kyle Mahlkuch > --- > Changes since v2: > - Capture ndlp and clear evt_arg1 under hbalock while dequeuing >   LPFC_EVT_ELS_RETRY in lpfc_work_list_done(). A requeue by >   lpfc_els_retry_delay() could cause a NULL dereference in the worker. >   (AI review) > - Whitespace and line-wrapping cleanup. > > Link: https://lore.kernel.org/lkml/29073ebc-b616-475b- > bc05-384da09fbb54@linux.ibm.com/T/#u > > Changes since v1: > - Leave test_and_clear_bit op and timer_delete_sync at the beginning of >   lpfc_cancel_retry_delay_tmo() outside of lock. (Paul Ely) > > Link: https://lore.kernel.org/lkml/1c8a764c-fce1-4ce1- > b797-47ac328cf3f2@linux.ibm.com/T/#u > --- >  drivers/scsi/lpfc/lpfc_els.c     | 29 +++++++++++++++++++++++------ >  drivers/scsi/lpfc/lpfc_hbadisc.c | 11 ++++++++++- >  2 files changed, 33 insertions(+), 7 deletions(-) > > diff --git a/drivers/scsi/lpfc/lpfc_els.c b/drivers/scsi/lpfc/lpfc_els.c > index 6f6394a0047c..98d1824aefe1 100644 > --- a/drivers/scsi/lpfc/lpfc_els.c > +++ b/drivers/scsi/lpfc/lpfc_els.c > @@ -4477,18 +4477,35 @@ lpfc_issue_els_edc(struct lpfc_vport *vport, > uint8_t retry) >  void >  lpfc_cancel_retry_delay_tmo(struct lpfc_vport *vport, struct > lpfc_nodelist *nlp) >  { > -    struct lpfc_work_evt *evtp; > +    struct lpfc_hba *phba = vport->phba; > +    struct lpfc_work_evt *evtp = &nlp->els_retry_evt; > +    struct lpfc_nodelist *arg_ndlp = NULL; > +    unsigned long flags; > >      if (!test_and_clear_bit(NLP_DELAY_TMO, &nlp->nlp_flag)) >          return; >      timer_delete_sync(&nlp->nlp_delayfunc); >      nlp->nlp_last_elscmd = 0; > -    if (!list_empty(&nlp->els_retry_evt.evt_listp)) { > -        list_del_init(&nlp->els_retry_evt.evt_listp); > -        /* Decrement nlp reference count held for the delayed retry */ > -        evtp = &nlp->els_retry_evt; > -        lpfc_nlp_put((struct lpfc_nodelist *)evtp->evt_arg1); > + > +    /* > +     * If retry event is queued, remove it under lock and consume > +     * its payload to prevent double-put. The event holds a reference > +     * to the nodelist that must be released exactly once. > +     */ > +    spin_lock_irqsave(&phba->hbalock, flags); > +    if (!list_empty(&evtp->evt_listp)) { > +        list_del_init(&evtp->evt_listp); > +        /* Take local copy and clear to prevent reuse */ > +        arg_ndlp = (struct lpfc_nodelist *)evtp->evt_arg1; > +        evtp->evt_arg1 = NULL; > +        smp_wmb(); /* Ensure NULL visible before unlock */ >      } > +    spin_unlock_irqrestore(&phba->hbalock, flags); > + > +    /* Drop the event-held reference outside the lock */ > +    if (arg_ndlp) > +        lpfc_nlp_put(arg_ndlp); > + >      if (test_and_clear_bit(NLP_NPR_2B_DISC, &nlp->nlp_flag)) { >          if (vport->num_disc_nodes) { >              if (vport->port_state < LPFC_VPORT_READY) { > diff --git a/drivers/scsi/lpfc/lpfc_hbadisc.c b/drivers/scsi/lpfc/ > lpfc_hbadisc.c > index 4c673dffa671..75457f19d4ea 100644 > --- a/drivers/scsi/lpfc/lpfc_hbadisc.c > +++ b/drivers/scsi/lpfc/lpfc_hbadisc.c > @@ -840,12 +840,21 @@ lpfc_work_list_done(struct lpfc_hba *phba) >      while (!list_empty(&phba->work_list)) { >          list_remove_head((&phba->work_list), evtp, typeof(*evtp), >                   evt_listp); > +        /* > +         * The ELS retry event can be requeued by lpfc_els_retry_delay() > +         * as soon as hbalock is dropped. Consume the payload within the > +         * hbalock to prevent reuse or double-put. > +         */ > +        if (evtp->evt == LPFC_EVT_ELS_RETRY) { > +            ndlp = (struct lpfc_nodelist *)(evtp->evt_arg1); > +            evtp->evt_arg1 = NULL; > +        } >          spin_unlock_irq(&phba->hbalock); >          hba_pci_err = test_bit(HBA_PCI_ERR, &phba->bit_flags); >          free_evt = 1; >          switch (evtp->evt) { >          case LPFC_EVT_ELS_RETRY: > -            ndlp = (struct lpfc_nodelist *) (evtp->evt_arg1); > +            /* ndlp was already captured under hbalock */ >              if (!hba_pci_err) { >                  lpfc_els_retry_delay_handler(ndlp); >                  free_evt = 0; /* evt is part of ndlp */ Good catch. Reviewed-by: Hannes Reinecke Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@suse.de +49 911 74053 688 SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. 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