RDMA/core: Avoid hmm_dma_map_alloc() for virtual DMA devices

Drivers such as rxe, which use virtual DMA, must not call into the DMA
mapping core since they lack physical DMA capabilities. Otherwise, a NULL
pointer dereference is observed as shown below. This patch ensures the RDMA
core handles virtual and physical DMA paths appropriately.

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           6.15.0-rc1+ #11 PREEMPT(voluntary)
 Tainted: [W]=WARN
 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 <f6> 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:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 00000000000002fc CR3: 000000010a1f0004 CR4: 0000000000f72ef0
 PKRU: 55555554
 Call Trace:
  <TASK>
  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
  </TASK>

Fixes: 1efe8c0670d6 ("RDMA/core: Convert UMEM ODP DMA mapping to caching IOVA and page linkage")
Closes: https://lore.kernel.org/all/3e8f343f-7d66-4f7a-9f08-3910623e322f@gmail.com/
Signed-off-by: Daisuke Matsuda <dskmtsd@gmail.com>
Link: https://patch.msgid.link/20250524144328.4361-1-dskmtsd@gmail.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>

2 files changed, 26 insertions, 8 deletions

diff --git a/drivers/infiniband/core/umem_odp.c b/drivers/infiniband/core/umem_odp.c
index 51d518989914..c752ae9fad6c 100644
--- a/drivers/infiniband/core/umem_odp.c
+++ b/drivers/infiniband/core/umem_odp.c
@@ -60,9 +60,11 @@ static int ib_init_umem_odp(struct ib_umem_odp *umem_odp,
 {
 	struct ib_device *dev = umem_odp->umem.ibdev;
 	size_t page_size = 1UL << umem_odp->page_shift;
+	struct hmm_dma_map *map;
 	unsigned long start;
 	unsigned long end;
-	int ret;
+	size_t nr_entries;
+	int ret = 0;
 
 	umem_odp->umem.is_odp = 1;
 	mutex_init(&umem_odp->umem_mutex);
@@ -75,9 +77,20 @@ static int ib_init_umem_odp(struct ib_umem_odp *umem_odp,
 	if (unlikely(end < page_size))
 		return -EOVERFLOW;
 
-	ret = hmm_dma_map_alloc(dev->dma_device, &umem_odp->map,
-				(end - start) >> PAGE_SHIFT,
-				1 << umem_odp->page_shift);
+	nr_entries = (end - start) >> PAGE_SHIFT;
+	if (!(nr_entries * PAGE_SIZE / page_size))
+		return -EINVAL;
+
+	map = &umem_odp->map;
+	if (ib_uses_virt_dma(dev)) {
+		map->pfn_list = kvcalloc(nr_entries, sizeof(*map->pfn_list),
+					 GFP_KERNEL | __GFP_NOWARN);
+		if (!map->pfn_list)
+			ret = -ENOMEM;
+	} else
+		ret = hmm_dma_map_alloc(dev->dma_device, map,
+					(end - start) >> PAGE_SHIFT,
+					1 << umem_odp->page_shift);
 	if (ret)
 		return ret;
 
@@ -90,7 +103,10 @@ static int ib_init_umem_odp(struct ib_umem_odp *umem_odp,
 	return 0;
 
 out_free_map:
-	hmm_dma_map_free(dev->dma_device, &umem_odp->map);
+	if (ib_uses_virt_dma(dev))
+		kfree(map->pfn_list);
+	else
+		hmm_dma_map_free(dev->dma_device, map);
 	return ret;
 }
 
@@ -259,7 +275,10 @@ static void ib_umem_odp_free(struct ib_umem_odp *umem_odp)
 				    ib_umem_end(umem_odp));
 	mutex_unlock(&umem_odp->umem_mutex);
 	mmu_interval_notifier_remove(&umem_odp->notifier);
-	hmm_dma_map_free(dev->dma_device, &umem_odp->map);
+	if (ib_uses_virt_dma(dev))
+		kfree(umem_odp->map.pfn_list);
+	else
+		hmm_dma_map_free(dev->dma_device, &umem_odp->map);
 }
 
 void ib_umem_odp_release(struct ib_umem_odp *umem_odp)
diff --git a/mm/hmm.c b/mm/hmm.c
index a8bf097677f3..feac86196a65 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -640,8 +640,7 @@ int hmm_dma_map_alloc(struct device *dev, struct hmm_dma_map *map,
 	bool dma_need_sync = false;
 	bool use_iova;
 
-	if (!(nr_entries * PAGE_SIZE / dma_entry_size))
-		return -EINVAL;
+	WARN_ON_ONCE(!(nr_entries * PAGE_SIZE / dma_entry_size));
 
 	/*
 	 * The HMM API violates our normal DMA buffer ownership rules and can't