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charset="us-ascii" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: oracle.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: SJ0PR10MB4688.namprd10.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 57b76744-7f4f-4ad6-9fbd-08d90c143f84 X-MS-Exchange-CrossTenant-originalarrivaltime: 30 Apr 2021 20:12:15.2518 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: zxzgL0fWrep1FQK7ejXt7FLtqLL/oiSeSzwjila3miNpNlB80199aJCC6LgquOM2govuYCKlbrannsyloDjFZQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ0PR10MB4669 X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=9970 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 bulkscore=0 mlxscore=0 malwarescore=0 phishscore=0 adultscore=0 mlxlogscore=999 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104060000 definitions=main-2104300140 X-Proofpoint-ORIG-GUID: 1hWWymk092CY4wzS1Fz1N_KS_AxBTS9n X-Proofpoint-GUID: 1hWWymk092CY4wzS1Fz1N_KS_AxBTS9n X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=9970 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 impostorscore=0 phishscore=0 spamscore=0 bulkscore=0 mlxscore=0 lowpriorityscore=0 clxscore=1015 suspectscore=0 malwarescore=0 mlxlogscore=999 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104060000 definitions=main-2104300140 Precedence: bulk List-ID: X-Mailing-List: linux-next@vger.kernel.org > On Apr 30, 2021, at 3:09 PM, Trond Myklebust wr= ote: >=20 > On Fri, 2021-04-30 at 18:45 +0000, Chuck Lever III wrote: >>=20 >>=20 >>> On Apr 30, 2021, at 2:26 PM, coverity-bot >>> wrote: >>>=20 >>> Hello! >>>=20 >>> This is an experimental semi-automated report about issues detected >>> by >>> Coverity from a scan of next-20210430 as part of the linux-next >>> scan project: >>> https://scan.coverity.com/projects/linux-next-weekly-scan >>>=20 >>> You're getting this email because you were associated with the >>> identified >>> lines of code (noted below) that were touched by commits: >>>=20 >>> Mon Apr 26 09:27:06 2021 -0400 >>> 9a301cafc861 ("xprtrdma: Move fr_linv_done field to struct >>> rpcrdma_mr") >>>=20 >>> Coverity reported the following: >>>=20 >>> *** CID 1504556: Null pointer dereferences (FORWARD_NULL) >>> /net/sunrpc/xprtrdma/frwr_ops.c: 539 in frwr_unmap_sync() >>> 533 >>> 534 /* Strong send queue ordering guarantees that when >>> the >>> 535 * last WR in the chain completes, all WRs in the >>> chain >>> 536 * are complete. >>> 537 */ >>> 538 last->wr_cqe->done =3D frwr_wc_localinv_wake; >>> vvv CID 1504556: Null pointer dereferences (FORWARD_NULL) >>> vvv Passing null pointer "&mr->mr_linv_done" to >>> "reinit_completion", which dereferences it. >>> 539 reinit_completion(&mr->mr_linv_done); >>> 540 >>> 541 /* Transport disconnect drains the receive CQ >>> before it >>> 542 * replaces the QP. The RPC reply handler won't >>> call us >>> 543 * unless re_id->qp is a valid pointer. >>> 544 */ >>>=20 >>> If this is a false positive, please let us know so we can mark it >>> as >>> such, or teach the Coverity rules to be smarter. >>=20 >> Sure, not my proudest moment here. >>=20 >> The sole call site for frwr_unmap_sync() is this one: >>=20 >> net/sunrpc/xprtrdma/transport.c: >> 606 if (unlikely(!list_empty(&req->rl_registered))) { >> 607 trace_xprtrdma_mrs_zap(task); >> 608 frwr_unmap_sync(rpcx_to_rdmax(rqst->rq_xprt), >> req); >> 609 } >>=20 >> Thus, in the current code base, the while() loop: >>=20 >> net/sunrpc/xprtrdma/frwr_ops.c: >> 514 while ((mr =3D rpcrdma_mr_pop(&req->rl_registered))) { >>=20 >> Should always terminate with mr containing a non-NULL address. >>=20 >> Seems to me the frwr_unmap_sync() code before fdf5ecb1934b >> ("xprtrdma: Move fr_linv_done field to struct rpcrdma_mr") has >> the same risk -- frwr can be NULL if rl_registered is empty. >>=20 >> I'm open to suggestions for improvement, but I'm not seeing this >> rise to the level of a pervasive and high impact issue. >>=20 >=20 > Chuck, I think the point is that you can't ever exit that while() loop > _unless_ mr =3D=3D NULL. So calling reinit_completion(&mr->mr_linv_done) > after exiting that loop will indeed Oops. D'oh. > So will the call to wait_for_completion(&mr->mr_linv_done). >=20 > IOW: I think you need to save the last non-NULL value of 'mr' inside > the loop. I think following the while() loop with: mr =3D container_of(last, struct rpcrdma_mr, mr_invwr); Might also work. -- Chuck Lever