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Mon, 02 Feb 2026 04:57:57 -0800 (PST) Received: from hu-pragalla-hyd.qualcomm.com ([202.46.23.25]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2a88b426ae4sm140852615ad.43.2026.02.02.04.57.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Feb 2026 04:57:57 -0800 (PST) From: Pradeep P V K To: kbusch@kernel.org, axboe@kernel.dk, hch@lst.de, sagi@grimberg.me Cc: linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, nitin.rawat@oss.qualcomm.com, Pradeep P V K Subject: [PATCH V1] nvme-pci: Fix NULL pointer dereference in nvme_pci_prp_iter_next Date: Mon, 2 Feb 2026 18:27:38 +0530 Message-Id: <20260202125738.1194899-1-pradeep.pragallapati@oss.qualcomm.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Authority-Analysis: v=2.4 cv=ANnNY0ku c=1 sm=1 tr=0 ts=69809f57 cx=c_pps a=MTSHoo12Qbhz2p7MsH1ifg==:117 a=ZePRamnt/+rB5gQjfz0u9A==:17 a=HzLeVaNsDn8A:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=EUspDBNiAAAA:8 a=4zosCYUxuotpryp6MGcA:9 a=GvdueXVYPmCkWapjIL-Q:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMjAyMDEwMSBTYWx0ZWRfX+y+ElnqjLf6m vR36iGar+yOVQLR2i1umCtpWo8rZ7XV7PGyYXPTyWxymg3O1ez1bm/yjf1kT+9eTMLsfIbBM/bE Yjt78zGu9AckxidQXqENvtPkUiz4SRDMOM5/PvMEyzxuqVXOH+xEOy6dON4RDJqrmsRCj85d1A3 qYvwRfl0y6vigEb+VImUkzGkhQlvX+Go9hSGa9ZpZ5Tkw1Tb3JdOQMz4VUQTimH4rW7j27qzp7v qA1FSHs+B8dj4ooWJzHFwQxFUjTOuL87DwjwppeZPuPM/PkgW8/sZVJrkhmO8XnW3yklOurj1Rx KIul8DhTsOK8qu4bdjG/e1lQZKucQUMc9q4b3kEeVUKcfHt/cmO2Uz82+8ivhVYNdO69fdXVydh w6h5kn8+OrI59H3I9/b6VMk7+mqLLEdLI6250OrhEtFUfOJativzW7DyH5faCWXzzbUdG7RsocS EWxLIwcoPz62sPMHEqw== X-Proofpoint-GUID: xoLPWxYMW-koC-rlXWoRCcnnoCmOqmGg X-Proofpoint-ORIG-GUID: xoLPWxYMW-koC-rlXWoRCcnnoCmOqmGg X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-02-02_04,2026-01-30_04,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 malwarescore=0 lowpriorityscore=0 clxscore=1015 bulkscore=0 spamscore=0 priorityscore=1501 impostorscore=0 phishscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2601150000 definitions=main-2602020101 Content-Type: text/plain; charset="utf-8" Fix a NULL pointer dereference that occurs in nvme_pci_prp_iter_next() when SWIOTLB bounce buffering becomes active during runtime. The issue occurs when SWIOTLB activation changes the device's DMA mapping requirements at runtime, creating a mismatch between iod->dma_vecs allocation and access logic. The problem manifests when: 1. Device initially operates with dma_skip_sync=3Dtrue (coherent DMA assumed) 2. First SWIOTLB mapping occurs due to DMA address limitations, memory encryption, or IOMMU bounce buffering requirements 3. SWIOTLB calls dma_reset_need_sync(), permanently setting dma_skip_sync=3Dfalse 4. Subsequent I/Os now have dma_need_unmap()=3Dtrue, requiring iod->dma_vecs The issue arises from the timing of allocation versus access: - nvme_pci_setup_data_prp() allocates iod->dma_vecs only when both (!dma_use_iova() && dma_need_unmap()) conditions are met - nvme_pci_prp_iter_next() assumes iod->dma_vecs is valid whenever the same conditions are true, without NULL checking - This creates a race where the device's DMA requirements change dynamically after the initial allocation decision, leading to NULL pointer access Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 pc : nvme_pci_prp_iter_next+0xe4/0x128 [nvme] Call trace: nvme_pci_prp_iter_next+0xe4/0x128 [nvme] nvme_prep_rq+0x5f4/0xa6c [nvme] nvme_queue_rqs+0xa8/0x18c [nvme] blk_mq_dispatch_queue_requests.constprop.0+0x108/0x120 blk_mq_flush_plug_list+0x8c/0x174 __blk_flush_plug+0xe4/0x140 blk_finish_plug+0x38/0x4c read_pages+0x184/0x288 page_cache_ra_order+0x1e0/0x3a4 filemap_fault+0x518/0xa90 __do_fault+0x3c/0x22c __handle_mm_fault+0x10ec/0x19b8 handle_mm_fault+0xb4/0x294 Fix this by: 1. Initialize iod->dma_vecs to NULL in nvme_prep_rq() 2. Add NULL pointer check before accessing iod->dma_vecs in nvme_pci_prp_iter_next() 3. Set iod->dma_vecs to NULL after freeing for defensive programming Fixes: b8b7570a7ec8 ("nvme-pci: fix dma unmapping when using PRPs and not u= sing the IOVA mapping") Co-developed-by: Nitin Rawat Signed-off-by: Nitin Rawat Signed-off-by: Pradeep P V K --- drivers/nvme/host/pci.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c index 2a52cf46d960..e235654e7ee0 100644 --- a/drivers/nvme/host/pci.c +++ b/drivers/nvme/host/pci.c @@ -720,6 +720,7 @@ static void nvme_free_prps(struct request *req, unsigne= d int attrs) dma_unmap_phys(nvmeq->dev->dev, iod->dma_vecs[i].addr, iod->dma_vecs[i].len, rq_dma_dir(req), attrs); mempool_free(iod->dma_vecs, nvmeq->dev->dmavec_mempool); + iod->dma_vecs =3D NULL; } =20 static void nvme_free_sgls(struct request *req, struct nvme_sgl_desc *sge, @@ -825,7 +826,7 @@ static bool nvme_pci_prp_iter_next(struct request *req,= struct device *dma_dev, return true; if (!blk_rq_dma_map_iter_next(req, dma_dev, iter)) return false; - if (!dma_use_iova(&iod->dma_state) && dma_need_unmap(dma_dev)) { + if (iod->dma_vecs && !dma_use_iova(&iod->dma_state) && dma_need_unmap(dma= _dev)) { iod->dma_vecs[iod->nr_dma_vecs].addr =3D iter->addr; iod->dma_vecs[iod->nr_dma_vecs].len =3D iter->len; iod->nr_dma_vecs++; @@ -1218,6 +1219,7 @@ static blk_status_t nvme_prep_rq(struct request *req) iod->nr_descriptors =3D 0; iod->total_len =3D 0; iod->meta_total_len =3D 0; + iod->dma_vecs =3D NULL; =20 ret =3D nvme_setup_cmd(req->q->queuedata, req); if (ret) --=20 2.34.1