From b63a74968b2955f4c45e5aa527321cbd02eb49f5 Mon Sep 17 00:00:00 2001 From: Benjamin Block Date: Fri, 9 Dec 2016 17:16:31 +0100 Subject: [PATCH] scsi: zfcp: fix use-after-"free" in FC ingress path after TMF commit dac37e15b7d511e026a9313c8c46794c144103cd upstream. When SCSI EH invokes zFCP's callbacks for eh_device_reset_handler() and eh_target_reset_handler(), it expects us to relent the ownership over the given scsi_cmnd and all other scsi_cmnds within the same scope - LUN or target - when returning with SUCCESS from the callback ('release' them). SCSI EH can then reuse those commands. We did not follow this rule to release commands upon SUCCESS; and if later a reply arrived for one of those supposed to be released commands, we would still make use of the scsi_cmnd in our ingress tasklet. This will at least result in undefined behavior or a kernel panic because of a wrong kernel pointer dereference. To fix this, we NULLify all pointers to scsi_cmnds (struct zfcp_fsf_req *)->data in the matching scope if a TMF was successful. This is done under the locks (struct zfcp_adapter *)->abort_lock and (struct zfcp_reqlist *)->lock to prevent the requests from being removed from the request-hashtable, and the ingress tasklet from making use of the scsi_cmnd-pointer in zfcp_fsf_fcp_cmnd_handler(). For cases where a reply arrives during SCSI EH, but before we get a chance to NULLify the pointer - but before we return from the callback -, we assume that the code is protected from races via the CAS operation in blk_complete_request() that is called in scsi_done(). The following stacktrace shows an example for a crash resulting from the previous behavior: Unable to handle kernel pointer dereference at virtual kernel address fffffee17a672000 Oops: 0038 [#1] SMP CPU: 2 PID: 0 Comm: swapper/2 Not tainted task: 00000003f7ff5be0 ti: 00000003f3d38000 task.ti: 00000003f3d38000 Krnl PSW : 0404d00180000000 00000000001156b0 (smp_vcpu_scheduled+0x18/0x40) R:0 T:1 IO:0 EX:0 Key:0 M:1 W:0 P:0 AS:3 CC:1 PM:0 EA:3 Krnl GPRS: 000000200000007e 0000000000000000 fffffee17a671fd8 0000000300000015 ffffffff80000000 00000000005dfde8 07000003f7f80e00 000000004fa4e800 000000036ce8d8f8 000000036ce8d9c0 00000003ece8fe00 ffffffff969c9e93 00000003fffffffd 000000036ce8da10 00000000003bf134 00000003f3b07918 Krnl Code: 00000000001156a2: a7190000 lghi %r1,0 00000000001156a6: a7380015 lhi %r3,21 #00000000001156aa: e32050000008 ag %r2,0(%r5) >00000000001156b0: 482022b0 lh %r2,688(%r2) 00000000001156b4: ae123000 sigp %r1,%r2,0(%r3) 00000000001156b8: b2220020 ipm %r2 00000000001156bc: 8820001c srl %r2,28 00000000001156c0: c02700000001 xilf %r2,1 Call Trace: ([<0000000000000000>] 0x0) [<000003ff807bdb8e>] zfcp_fsf_fcp_cmnd_handler+0x3de/0x490 [zfcp] [<000003ff807be30a>] zfcp_fsf_req_complete+0x252/0x800 [zfcp] [<000003ff807c0a48>] zfcp_fsf_reqid_check+0xe8/0x190 [zfcp] [<000003ff807c194e>] zfcp_qdio_int_resp+0x66/0x188 [zfcp] [<000003ff80440c64>] qdio_kick_handler+0xdc/0x310 [qdio] [<000003ff804463d0>] __tiqdio_inbound_processing+0xf8/0xcd8 [qdio] [<0000000000141fd4>] tasklet_action+0x9c/0x170 [<0000000000141550>] __do_softirq+0xe8/0x258 [<000000000010ce0a>] do_softirq+0xba/0xc0 [<000000000014187c>] irq_exit+0xc4/0xe8 [<000000000046b526>] do_IRQ+0x146/0x1d8 [<00000000005d6a3c>] io_return+0x0/0x8 [<00000000005d6422>] vtime_stop_cpu+0x4a/0xa0 ([<0000000000000000>] 0x0) [<0000000000103d8a>] arch_cpu_idle+0xa2/0xb0 [<0000000000197f94>] cpu_startup_entry+0x13c/0x1f8 [<0000000000114782>] smp_start_secondary+0xda/0xe8 [<00000000005d6efe>] restart_int_handler+0x56/0x6c [<0000000000000000>] 0x0 Last Breaking-Event-Address: [<00000000003bf12e>] arch_spin_lock_wait+0x56/0xb0 Suggested-by: Steffen Maier Signed-off-by: Benjamin Block Fixes: ea127f9754 ("[PATCH] s390 (7/7): zfcp host adapter.") (tglx/history.git) Signed-off-by: Steffen Maier Signed-off-by: Martin K. Petersen [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings --- drivers/s390/scsi/zfcp_dbf.h | 11 ++++++ drivers/s390/scsi/zfcp_reqlist.h | 30 ++++++++++++++++- drivers/s390/scsi/zfcp_scsi.c | 57 ++++++++++++++++++++++++++++++-- 3 files changed, 95 insertions(+), 3 deletions(-) diff --git a/drivers/s390/scsi/zfcp_dbf.h b/drivers/s390/scsi/zfcp_dbf.h index 440aa619da1d..e7839ecaf332 100644 --- a/drivers/s390/scsi/zfcp_dbf.h +++ b/drivers/s390/scsi/zfcp_dbf.h @@ -388,4 +388,15 @@ void zfcp_dbf_scsi_devreset(char *tag, struct scsi_cmnd *scmnd, u8 flag) _zfcp_dbf_scsi(tmp_tag, 1, scmnd, NULL); } +/** + * zfcp_dbf_scsi_nullcmnd() - trace NULLify of SCSI command in dev/tgt-reset. + * @scmnd: SCSI command that was NULLified. + * @fsf_req: request that owned @scmnd. + */ +static inline void zfcp_dbf_scsi_nullcmnd(struct scsi_cmnd *scmnd, + struct zfcp_fsf_req *fsf_req) +{ + _zfcp_dbf_scsi("scfc__1", 3, scmnd, fsf_req); +} + #endif /* ZFCP_DBF_H */ diff --git a/drivers/s390/scsi/zfcp_reqlist.h b/drivers/s390/scsi/zfcp_reqlist.h index a72d1b730aba..703fce59befe 100644 --- a/drivers/s390/scsi/zfcp_reqlist.h +++ b/drivers/s390/scsi/zfcp_reqlist.h @@ -4,7 +4,7 @@ * Data structure and helper functions for tracking pending FSF * requests. * - * Copyright IBM Corporation 2009 + * Copyright IBM Corp. 2009, 2016 */ #ifndef ZFCP_REQLIST_H @@ -180,4 +180,32 @@ static inline void zfcp_reqlist_move(struct zfcp_reqlist *rl, spin_unlock_irqrestore(&rl->lock, flags); } +/** + * zfcp_reqlist_apply_for_all() - apply a function to every request. + * @rl: the requestlist that contains the target requests. + * @f: the function to apply to each request; the first parameter of the + * function will be the target-request; the second parameter is the same + * pointer as given with the argument @data. + * @data: freely chosen argument; passed through to @f as second parameter. + * + * Uses :c:macro:`list_for_each_entry` to iterate over the lists in the hash- + * table (not a 'safe' variant, so don't modify the list). + * + * Holds @rl->lock over the entire request-iteration. + */ +static inline void +zfcp_reqlist_apply_for_all(struct zfcp_reqlist *rl, + void (*f)(struct zfcp_fsf_req *, void *), void *data) +{ + struct zfcp_fsf_req *req; + unsigned long flags; + unsigned int i; + + spin_lock_irqsave(&rl->lock, flags); + for (i = 0; i < ZFCP_REQ_LIST_BUCKETS; i++) + list_for_each_entry(req, &rl->buckets[i], list) + f(req, data); + spin_unlock_irqrestore(&rl->lock, flags); +} + #endif /* ZFCP_REQLIST_H */ diff --git a/drivers/s390/scsi/zfcp_scsi.c b/drivers/s390/scsi/zfcp_scsi.c index 38ee0df633a3..0bbc2a9a95c5 100644 --- a/drivers/s390/scsi/zfcp_scsi.c +++ b/drivers/s390/scsi/zfcp_scsi.c @@ -3,7 +3,7 @@ * * Interface to Linux SCSI midlayer. * - * Copyright IBM Corp. 2002, 2015 + * Copyright IBM Corp. 2002, 2016 */ #define KMSG_COMPONENT "zfcp" @@ -230,6 +230,57 @@ static int zfcp_scsi_eh_abort_handler(struct scsi_cmnd *scpnt) return retval; } +struct zfcp_scsi_req_filter { + u8 tmf_scope; + u32 lun_handle; + u32 port_handle; +}; + +static void zfcp_scsi_forget_cmnd(struct zfcp_fsf_req *old_req, void *data) +{ + struct zfcp_scsi_req_filter *filter = + (struct zfcp_scsi_req_filter *)data; + + /* already aborted - prevent side-effects - or not a SCSI command */ + if (old_req->data == NULL || old_req->fsf_command != FSF_QTCB_FCP_CMND) + return; + + /* (tmf_scope == FCP_TMF_TGT_RESET || tmf_scope == FCP_TMF_LUN_RESET) */ + if (old_req->qtcb->header.port_handle != filter->port_handle) + return; + + if (filter->tmf_scope == FCP_TMF_LUN_RESET && + old_req->qtcb->header.lun_handle != filter->lun_handle) + return; + + zfcp_dbf_scsi_nullcmnd((struct scsi_cmnd *)old_req->data, old_req); + old_req->data = NULL; +} + +static void zfcp_scsi_forget_cmnds(struct zfcp_scsi_dev *zsdev, u8 tm_flags) +{ + struct zfcp_adapter *adapter = zsdev->port->adapter; + struct zfcp_scsi_req_filter filter = { + .tmf_scope = FCP_TMF_TGT_RESET, + .port_handle = zsdev->port->handle, + }; + unsigned long flags; + + if (tm_flags == FCP_TMF_LUN_RESET) { + filter.tmf_scope = FCP_TMF_LUN_RESET; + filter.lun_handle = zsdev->lun_handle; + } + + /* + * abort_lock secures against other processings - in the abort-function + * and normal cmnd-handler - of (struct zfcp_fsf_req *)->data + */ + write_lock_irqsave(&adapter->abort_lock, flags); + zfcp_reqlist_apply_for_all(adapter->req_list, zfcp_scsi_forget_cmnd, + &filter); + write_unlock_irqrestore(&adapter->abort_lock, flags); +} + static int zfcp_task_mgmt_function(struct scsi_cmnd *scpnt, u8 tm_flags) { struct zfcp_scsi_dev *zfcp_sdev = sdev_to_zfcp(scpnt->device); @@ -262,8 +313,10 @@ static int zfcp_task_mgmt_function(struct scsi_cmnd *scpnt, u8 tm_flags) if (fsf_req->status & ZFCP_STATUS_FSFREQ_TMFUNCFAILED) { zfcp_dbf_scsi_devreset("fail", scpnt, tm_flags); retval = FAILED; - } else + } else { zfcp_dbf_scsi_devreset("okay", scpnt, tm_flags); + zfcp_scsi_forget_cmnds(zfcp_sdev, tm_flags); + } zfcp_fsf_req_free(fsf_req); return retval; -- 2.39.2