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[119.244.79.106]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-b26eaf5a2cesm12884264a12.9.2025.05.23.07.36.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 23 May 2025 07:36:16 -0700 (PDT) From: Daisuke Matsuda To: linux-rdma@vger.kernel.org, linux-mm@kvack.org, leon@kernel.org, jgg@ziepe.ca, akpm@linux-foundation.org, jglisse@redhat.com Cc: linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, zyjzyj2000@gmail.com, Daisuke Matsuda Subject: [PATCH] mm/hmm: Allow hmm_dma_map_alloc() to tolerate NULL device Date: Fri, 23 May 2025 14:35:37 +0000 Message-ID: <20250523143537.10362-1-dskmtsd@gmail.com> X-Mailer: git-send-email 2.43.0 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 Content-Type: text/plain; charset="utf-8" Some drivers (such as rxe) may legitimately call hmm_dma_map_alloc() with a NULL device pointer, which leads to a NULL pointer dereference. This patch adds NULL checks to safely bypass device-specific DMA features when no device is provided. This fixes the following kernel oops: BUG: kernel NULL pointer dereference, address: 00000000000002fc #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 1028eb067 P4D 1028eb067 PUD 105da0067 PMD 0 Oops: Oops: 0000 [#1] SMP NOPTI CPU: 3 UID: 1000 PID: 1854 Comm: python3 Tainted: G W 6.1= 5.0-rc1+ #11 PREEMPT(voluntary) Tainted: [W]=3DWARN Hardware name: Trigkey Key N/Key N, BIOS KEYN101 09/02/2024 RIP: 0010:hmm_dma_map_alloc+0x25/0x100 Code: 90 90 90 90 90 0f 1f 44 00 00 55 48 89 e5 41 57 41 56 49 89 d6 49 c1= e6 0c 41 55 41 54 53 49 39 ce 0f 82 c6 00 00 00 49 89 fc 87 fc 02 00 = 00 20 0f 84 af 00 00 00 49 89 f5 48 89 d3 49 89 cf RSP: 0018:ffffd3d3420eb830 EFLAGS: 00010246 RAX: 0000000000001000 RBX: ffff8b727c7f7400 RCX: 0000000000001000 RDX: 0000000000000001 RSI: ffff8b727c7f74b0 RDI: 0000000000000000 RBP: ffffd3d3420eb858 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: 00007262a622a000 R14: 0000000000001000 R15: ffff8b727c7f74b0 FS: 00007262a62a1080(0000) GS:ffff8b762ac3e000(0000) knlGS:00000000000000= 00 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000000002fc CR3: 000000010a1f0004 CR4: 0000000000f72ef0 PKRU: 55555554 Call Trace: ib_init_umem_odp+0xb6/0x110 [ib_uverbs] ib_umem_odp_get+0xf0/0x150 [ib_uverbs] rxe_odp_mr_init_user+0x71/0x170 [rdma_rxe] rxe_reg_user_mr+0x217/0x2e0 [rdma_rxe] ib_uverbs_reg_mr+0x19e/0x2e0 [ib_uverbs] ib_uverbs_handler_UVERBS_METHOD_INVOKE_WRITE+0xd9/0x150 [ib_uverbs] ib_uverbs_cmd_verbs+0xd19/0xee0 [ib_uverbs] ? mmap_region+0x63/0xd0 ? __pfx_ib_uverbs_handler_UVERBS_METHOD_INVOKE_WRITE+0x10/0x10 [ib_uverbs] ib_uverbs_ioctl+0xba/0x130 [ib_uverbs] __x64_sys_ioctl+0xa4/0xe0 x64_sys_call+0x1178/0x2660 do_syscall_64+0x7e/0x170 ? syscall_exit_to_user_mode+0x4e/0x250 ? do_syscall_64+0x8a/0x170 ? do_syscall_64+0x8a/0x170 ? syscall_exit_to_user_mode+0x4e/0x250 ? do_syscall_64+0x8a/0x170 ? syscall_exit_to_user_mode+0x4e/0x250 ? do_syscall_64+0x8a/0x170 ? do_user_addr_fault+0x1d2/0x8d0 ? irqentry_exit_to_user_mode+0x43/0x250 ? irqentry_exit+0x43/0x50 ? exc_page_fault+0x93/0x1d0 entry_SYSCALL_64_after_hwframe+0x76/0x7e RIP: 0033:0x7262a6124ded Code: 04 25 28 00 00 00 48 89 45 c8 31 c0 48 8d 45 10 c7 45 b0 10 00 00 00= 48 89 45 b8 48 8d 45 d0 48 89 45 c0 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 = ff ff 77 1a 48 8b 45 c8 64 48 2b 04 25 28 00 00 00 RSP: 002b:00007fffd08c3960 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fffd08c39f0 RCX: 00007262a6124ded RDX: 00007fffd08c3a10 RSI: 00000000c0181b01 RDI: 0000000000000007 RBP: 00007fffd08c39b0 R08: 0000000014107820 R09: 00007fffd08c3b44 R10: 000000000000000c R11: 0000000000000246 R12: 00007fffd08c3b44 R13: 000000000000000c R14: 00007fffd08c3b58 R15: 0000000014107960 Fixes: 1efe8c0670d6 ("RDMA/core: Convert UMEM ODP DMA mapping to caching IO= VA and page linkage") Closes: https://lore.kernel.org/all/3e8f343f-7d66-4f7a-9f08-3910623e322f@gm= ail.com/ Signed-off-by: Daisuke Matsuda --- mm/hmm.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/mm/hmm.c b/mm/hmm.c index a8bf097677f3..311141124e67 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -638,7 +638,7 @@ int hmm_dma_map_alloc(struct device *dev, struct hmm_dm= a_map *map, size_t nr_entries, size_t dma_entry_size) { bool dma_need_sync =3D false; - bool use_iova; + bool use_iova =3D false; =20 if (!(nr_entries * PAGE_SIZE / dma_entry_size)) return -EINVAL; @@ -649,9 +649,9 @@ int hmm_dma_map_alloc(struct device *dev, struct hmm_dm= a_map *map, * best approximation to ensure no swiotlb buffering happens. */ #ifdef CONFIG_DMA_NEED_SYNC - dma_need_sync =3D !dev->dma_skip_sync; + dma_need_sync =3D dev ? !dev->dma_skip_sync : false; #endif /* CONFIG_DMA_NEED_SYNC */ - if (dma_need_sync || dma_addressing_limited(dev)) + if (dev && (dma_need_sync || dma_addressing_limited(dev))) return -EOPNOTSUPP; =20 map->dma_entry_size =3D dma_entry_size; @@ -660,9 +660,11 @@ int hmm_dma_map_alloc(struct device *dev, struct hmm_d= ma_map *map, if (!map->pfn_list) return -ENOMEM; =20 - use_iova =3D dma_iova_try_alloc(dev, &map->state, 0, - nr_entries * PAGE_SIZE); - if (!use_iova && dma_need_unmap(dev)) { + if (dev) + use_iova =3D dma_iova_try_alloc(dev, &map->state, 0, + nr_entries * PAGE_SIZE); + + if (!dev || (!use_iova && dma_need_unmap(dev))) { map->dma_list =3D kvcalloc(nr_entries, sizeof(*map->dma_list), GFP_KERNEL | __GFP_NOWARN); if (!map->dma_list) --=20 2.43.0