IB/uverbs: Fix OOPs in uverbs_user_mmap_disassociate

yishaih · jgunthorpe · commit 7b21b69ab203 · 2019-01-29T13:57:22.000-07:00
The vma->vm_mm can become impossible to get before rdma_umap_close() is called, in this case we must not try to get an mm that is already undergoing process exit. In this case there is no need to wait for anything as the VMA will be destroyed by another thread soon and is already effectively 'unreachable' by userspace. BUG: unable to handle kernel NULL pointer dereference at 0000000000000000 PGD 800000012bc50067 P4D 800000012bc50067 PUD 129db5067 PMD 0 Oops: 0000 [#1] SMP PTI CPU: 1 PID: 2050 Comm: bash Tainted: G W OE 4.20.0-rc6+ #3 Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011 RIP: 0010:__rb_erase_color+0xb9/0x280 Code: 84 17 01 00 00 48 3b 68 10 0f 84 15 01 00 00 48 89 58 08 48 89 de 48 89 ef 4c 89 e3 e8 90 84 22 00 e9 60 ff ff ff 48 8b 5d 10 <f6> 03 01 0f 84 9c 00 00 00 48 8b 43 10 48 85 c0 74 09 f6 00 01 0f RSP: 0018:ffffbecfc090bab8 EFLAGS: 00010246 RAX: ffff97616346cf30 RBX: 0000000000000000 RCX: 0000000000000101 RDX: 0000000000000000 RSI: ffff97623b6ca828 RDI: ffff97621ef10828 RBP: ffff97621ef10828 R08: ffff97621ef10828 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff97623b6ca838 R13: ffffffffbb3fef50 R14: ffff97623b6ca828 R15: 0000000000000000 FS: 00007f7a5c31d740(0000) GS:ffff97623bb00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 000000011255a000 CR4: 00000000000006e0 Call Trace: unlink_file_vma+0x3b/0x50 free_pgtables+0xa1/0x110 exit_mmap+0xca/0x1a0 ? mlx5_ib_dealloc_pd+0x28/0x30 [mlx5_ib] mmput+0x54/0x140 uverbs_user_mmap_disassociate+0xcc/0x160 [ib_uverbs] uverbs_destroy_ufile_hw+0xf7/0x120 [ib_uverbs] ib_uverbs_remove_one+0xea/0x240 [ib_uverbs] ib_unregister_device+0xfb/0x200 [ib_core] mlx5_ib_remove+0x51/0xe0 [mlx5_ib] mlx5_remove_device+0xc1/0xd0 [mlx5_core] mlx5_unregister_device+0x3d/0xb0 [mlx5_core] remove_one+0x2a/0x90 [mlx5_core] pci_device_remove+0x3b/0xc0 device_release_driver_internal+0x16d/0x240 unbind_store+0xb2/0x100 kernfs_fop_write+0x102/0x180 __vfs_write+0x36/0x1a0 ? __alloc_fd+0xa9/0x170 ? set_close_on_exec+0x49/0x70 vfs_write+0xad/0x1a0 ksys_write+0x52/0xc0 do_syscall_64+0x5b/0x180 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Cc: <stable@vger.kernel.org> # 4.19 Fixes: 5f9794d ("RDMA/ucontext: Add a core API for mmaping driver IO memory") Signed-off-by: Yishai Hadas <yishaih@mellanox.com> Signed-off-by: Leon Romanovsky <leonro@mellanox.com> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c
@@ -967,11 +967,19 @@ void uverbs_user_mmap_disassociate(struct ib_uverbs_file *ufile)
 
 		/* Get an arbitrary mm pointer that hasn't been cleaned yet */
 		mutex_lock(&ufile->umap_lock);
-		if (!list_empty(&ufile->umaps)) {
-			mm = list_first_entry(&ufile->umaps,
-					      struct rdma_umap_priv, list)
-				     ->vma->vm_mm;
-			mmget(mm);
+		while (!list_empty(&ufile->umaps)) {
+			int ret;
+
+			priv = list_first_entry(&ufile->umaps,
+						struct rdma_umap_priv, list);
+			mm = priv->vma->vm_mm;
+			ret = mmget_not_zero(mm);
+			if (!ret) {
+				list_del_init(&priv->list);
+				mm = NULL;
+				continue;
+			}
+			break;
 		}
 		mutex_unlock(&ufile->umap_lock);
 		if (!mm)
