fuse: virtio_fs: Fix kernel null pointer dereference

BUG: kernel NULL pointer dereference, address: 0000000000000000
[    2.535283] #PF: supervisor write access in kernel mode
[    2.535769] #PF: error_code(0x0002) - not-present page
[    2.536395] PGD 107b37067 P4D 107b37067 PUD 107b38067 PMD 0
[    2.537158] Oops: Oops: 0002 [#1] SMP NOPTI
[    2.537802] CPU: 4 UID: 0 PID: 152 Comm: WSLGd Not tainted 6.17.0-rc4-WSL2+ torvalds#59 PREEMPT(none)
[    2.539416] RIP: 0010:virtio_fs_direct_access+0x6f/0xa0
[    2.540356] Code: 00 00 48 01 c6 49 89 75 00 48 85 ed 74 0e 48 8b b1 88 00 00 00 48 01 c6 48 89 75 00 48 03 81 88 00 00 00 48 c1 e8 0c 48 39 d3 <48> 89 45 00 48 89 d0 48 0f 46 c3 5b 5d 41 5c 41 5d 31 d2 31 c9 31
[    2.543093] RSP: 0018:ffffbdf8c2ec7c08 EFLAGS: 00010206
[    2.543647] RAX: 0000000000a00000 RBX: 000fffffffffffff RCX: ffff9f6e91171f00
[    2.544456] RDX: 0000000000200000 RSI: 0000000000000000 RDI: 000000000000000c
[    2.545348] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
[    2.546233] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
[    2.547036] R13: 0000000000000000 R14: ffff9f6e82d8ab00 R15: ffff9f6e84152480
[    2.547878] FS:  000075fe7e256800(0000) GS:ffff9f71c0968000(0000) knlGS:0000000000000000
[    2.548814] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    2.549730] CR2: 0000000000000000 CR3: 0000000107b2f000 CR4: 0000000000350ef0
[    2.550750] Call Trace:
[    2.551031]  <TASK>
[    2.551418]  dax_direct_access+0x35/0xc0
[    2.551993]  fuse_dax_conn_alloc+0x118/0x2e0
[    2.552660]  fuse_fill_super_common+0xf1/0x440
[    2.553436]  ? __kmalloc_cache_noprof+0x149/0x410
[    2.554110]  ? fuse_dev_alloc+0x7d/0x100
[    2.554925]  ? shrinker_register+0x8c/0xb0
[    2.555349]  virtio_fs_get_tree+0x35b/0x460
[    2.555850]  vfs_get_tree+0x29/0xe0
[    2.556203]  path_mount+0x582/0xac0
[    2.556953]  __x64_sys_mount+0x11d/0x150
[    2.557786]  do_syscall_64+0x72/0xb00
[    2.559436]  ? do_syscall_64+0x72/0xb00
[    2.559818]  ? do_syscall_64+0x72/0xb00
[    2.560449]  ? exc_page_fault+0x69/0x150
[    2.560719]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
[    2.561167] RIP: 0033:0x75fe80ca92ce
[    2.561720] Code: 48 8b 0d 4d 3b 0e 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 1a 3b 0e 00 f7 d8 64 89 01 48
[    2.563792] RSP: 002b:00007ffd31c720a8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
[    2.564707] RAX: ffffffffffffffda RBX: 00007ffd31c72138 RCX: 000075fe80ca92ce
[    2.565596] RDX: 000000000040d48f RSI: 000000000040d47c RDI: 000000000040d74a
[    2.566431] RBP: 00007ffd31c73f5b R08: 000000000040d498 R09: 0000000000000000
[    2.567439] R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffd31c73e43
[    2.568466] R13: 00007ffd31c73fc3 R14: 000075fe80d95500 R15: 000075fe7e256770
[    2.569408]  </TASK>
[    2.569755] Modules linked in:
[    2.570124] CR2: 0000000000000000
[    2.570532] ---[ end trace 0000000000000000 ]---
[    2.571164] RIP: 0010:virtio_fs_direct_access+0x6f/0xa0
[    2.571860] Code: 00 00 48 01 c6 49 89 75 00 48 85 ed 74 0e 48 8b b1 88 00 00 00 48 01 c6 48 89 75 00 48 03 81 88 00 00 00 48 c1 e8 0c 48 39 d3 <48> 89 45 00 48 89 d0 48 0f 46 c3 5b 5d 41 5c 41 5d 31 d2 31 c9 31
[    2.574309] RSP: 0018:ffffbdf8c2ec7c08 EFLAGS: 00010206
[    2.575423] RAX: 0000000000a00000 RBX: 000fffffffffffff RCX: ffff9f6e91171f00
[    2.576827] RDX: 0000000000200000 RSI: 0000000000000000 RDI: 000000000000000c
[    2.577479] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
[    2.578149] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
[    2.578825] R13: 0000000000000000 R14: ffff9f6e82d8ab00 R15: ffff9f6e84152480
[    2.579618] FS:  000075fe7e256800(0000) GS:ffff9f71c0968000(0000) knlGS:0000000000000000
[    2.580636] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    2.581196] CR2: 0000000000000000 CR3: 0000000107b2f000 CR4: 0000000000350ef0
[    2.582207] Kernel panic - not syncing: Fatal exception

Author: Aaradin86

fs/fuse/virtio_fs.c

@@ -1016,7 +1016,7 @@ static long virtio_fs_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
 	if (kaddr)
 		*kaddr = fs->window_kaddr + offset;
 	if (pfn)
-		*pfn = fs->window_phys_addr + offset;
+		*pfn = PHYS_PFN(fs->window_phys_addr + offset);
 	return nr_pages > max_nr_pages ? max_nr_pages : nr_pages;
 }