f2fs: give message and set need_fsck given broken node id

syzbot hit the following crash on upstream commit
83beed7b2b26f232d782127792dd0cd4362fdc41 (Fri Apr 20 17:56:32 2018 +0000)
Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/evalenti/linux-soc-thermal
syzbot dashboard link: https://syzkaller.appspot.com/bug?extid=d154ec99402c6f628887

C reproducer: https://syzkaller.appspot.com/x/repro.c?id=5414336294027264
syzkaller reproducer: https://syzkaller.appspot.com/x/repro.syz?id=5471683234234368
Raw console output: https://syzkaller.appspot.com/x/log.txt?id=5436660795834368
Kernel config: https://syzkaller.appspot.com/x/.config?id=1808800213120130118
compiler: gcc (GCC) 8.0.1 20180413 (experimental)

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+d154ec99402c6f628887@syzkaller.appspotmail.com
It will help syzbot understand when the bug is fixed. See footer for details.
If you forward the report, please keep this part and the footer.

F2FS-fs (loop0): Magic Mismatch, valid(0xf2f52010) - read(0x0)
F2FS-fs (loop0): Can't find valid F2FS filesystem in 1th superblock
F2FS-fs (loop0): invalid crc value
------------[ cut here ]------------
kernel BUG at fs/f2fs/node.c:1185!
invalid opcode: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 4549 Comm: syzkaller704305 Not tainted 4.17.0-rc1+ #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:__get_node_page+0xb68/0x16e0 fs/f2fs/node.c:1185
RSP: 0018:ffff8801d960e820 EFLAGS: 00010293
RAX: ffff8801d88205c0 RBX: 0000000000000003 RCX: ffffffff82f6cc06
RDX: 0000000000000000 RSI: ffffffff82f6d5e8 RDI: 0000000000000004
RBP: ffff8801d960ec30 R08: ffff8801d88205c0 R09: ffffed003b5e46c2
R10: 0000000000000003 R11: 0000000000000003 R12: ffff8801a86e00c0
R13: 0000000000000001 R14: ffff8801a86e0530 R15: ffff8801d9745240
FS:  000000000072c880(0000) GS:ffff8801daf00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f3d403209b8 CR3: 00000001d8f3f000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 get_node_page fs/f2fs/node.c:1237 [inline]
 truncate_xattr_node+0x152/0x2e0 fs/f2fs/node.c:1014
 remove_inode_page+0x200/0xaf0 fs/f2fs/node.c:1039
 f2fs_evict_inode+0xe86/0x1710 fs/f2fs/inode.c:547
 evict+0x4a6/0x960 fs/inode.c:557
 iput_final fs/inode.c:1519 [inline]
 iput+0x62d/0xa80 fs/inode.c:1545
 f2fs_fill_super+0x5f4e/0x7bf0 fs/f2fs/super.c:2849
 mount_bdev+0x30c/0x3e0 fs/super.c:1164
 f2fs_mount+0x34/0x40 fs/f2fs/super.c:3020
 mount_fs+0xae/0x328 fs/super.c:1267
 vfs_kern_mount.part.34+0xd4/0x4d0 fs/namespace.c:1037
 vfs_kern_mount fs/namespace.c:1027 [inline]
 do_new_mount fs/namespace.c:2518 [inline]
 do_mount+0x564/0x3070 fs/namespace.c:2848
 ksys_mount+0x12d/0x140 fs/namespace.c:3064
 __do_sys_mount fs/namespace.c:3078 [inline]
 __se_sys_mount fs/namespace.c:3075 [inline]
 __x64_sys_mount+0xbe/0x150 fs/namespace.c:3075
 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x443dea
RSP: 002b:00007ffcc7882368 EFLAGS: 00000297 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000020000c00 RCX: 0000000000443dea
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007ffcc7882370
RBP: 0000000000000003 R08: 0000000020016a00 R09: 000000000000000a
R10: 0000000000000000 R11: 0000000000000297 R12: 0000000000000004
R13: 0000000000402ce0 R14: 0000000000000000 R15: 0000000000000000
RIP: __get_node_page+0xb68/0x16e0 fs/f2fs/node.c:1185 RSP: ffff8801d960e820
---[ end trace 4edbeb71f002bb76 ]---

Reported-and-tested-by: syzbot+d154ec99402c6f628887@syzkaller.appspotmail.com
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/f2fs.h

@@ -1585,18 +1585,6 @@ static inline bool __exist_node_summaries(struct f2fs_sb_info *sbi)
 			is_set_ckpt_flags(sbi, CP_FASTBOOT_FLAG));
 }
 
-/*
- * Check whether the given nid is within node id range.
- */
-static inline int check_nid_range(struct f2fs_sb_info *sbi, nid_t nid)
-{
-	if (unlikely(nid < F2FS_ROOT_INO(sbi)))
-		return -EINVAL;
-	if (unlikely(nid >= NM_I(sbi)->max_nid))
-		return -EINVAL;
-	return 0;
-}
-
 /*
  * Check whether the inode has blocks or not
  */
@@ -2770,6 +2758,7 @@ f2fs_hash_t f2fs_dentry_hash(const struct qstr *name_info,
 struct dnode_of_data;
 struct node_info;
 
+int check_nid_range(struct f2fs_sb_info *sbi, nid_t nid);
 bool available_free_memory(struct f2fs_sb_info *sbi, int type);
 int need_dentry_mark(struct f2fs_sb_info *sbi, nid_t nid);
 bool is_checkpointed_node(struct f2fs_sb_info *sbi, nid_t nid);

fs/f2fs/inode.c

@@ -194,12 +194,8 @@ static int do_read_inode(struct inode *inode)
 	projid_t i_projid;
 
 	/* Check if ino is within scope */
-	if (check_nid_range(sbi, inode->i_ino)) {
-		f2fs_msg(inode->i_sb, KERN_ERR, "bad inode number: %lu",
-			 (unsigned long) inode->i_ino);
-		WARN_ON(1);
+	if (check_nid_range(sbi, inode->i_ino))
 		return -EINVAL;
-	}
 
 	node_page = get_node_page(sbi, inode->i_ino);
 	if (IS_ERR(node_page))
@@ -588,8 +584,11 @@ no_delete:
 		alloc_nid_failed(sbi, inode->i_ino);
 		clear_inode_flag(inode, FI_FREE_NID);
 	} else {
-		f2fs_bug_on(sbi, err &&
-			!exist_written_data(sbi, inode->i_ino, ORPHAN_INO));
+		/*
+		 * If xattr nid is corrupted, we can reach out error condition,
+		 * err & !exist_written_data(sbi, inode->i_ino, ORPHAN_INO)).
+		 * In that case, check_nid_range() is enough to give a clue.
+		 */
 	}
 out_clear:
 	fscrypt_put_encryption_info(inode);

fs/f2fs/node.c

@@ -29,6 +29,21 @@ static struct kmem_cache *nat_entry_slab;
 static struct kmem_cache *free_nid_slab;
 static struct kmem_cache *nat_entry_set_slab;
 
+/*
+ * Check whether the given nid is within node id range.
+ */
+int check_nid_range(struct f2fs_sb_info *sbi, nid_t nid)
+{
+	if (unlikely(nid < F2FS_ROOT_INO(sbi) || nid >= NM_I(sbi)->max_nid)) {
+		set_sbi_flag(sbi, SBI_NEED_FSCK);
+		f2fs_msg(sbi->sb, KERN_WARNING,
+				"%s: out-of-range nid=%x, run fsck to fix.",
+				__func__, nid);
+		return -EINVAL;
+	}
+	return 0;
+}
+
 bool available_free_memory(struct f2fs_sb_info *sbi, int type)
 {
 	struct f2fs_nm_info *nm_i = NM_I(sbi);
@@ -1158,7 +1173,8 @@ void ra_node_page(struct f2fs_sb_info *sbi, nid_t nid)
 
 	if (!nid)
 		return;
-	f2fs_bug_on(sbi, check_nid_range(sbi, nid));
+	if (check_nid_range(sbi, nid))
+		return;
 
 	rcu_read_lock();
 	apage = radix_tree_lookup(&NODE_MAPPING(sbi)->i_pages, nid);
@@ -1182,7 +1198,8 @@ static struct page *__get_node_page(struct f2fs_sb_info *sbi, pgoff_t nid,
 
 	if (!nid)
 		return ERR_PTR(-ENOENT);
-	f2fs_bug_on(sbi, check_nid_range(sbi, nid));
+	if (check_nid_range(sbi, nid))
+		return ERR_PTR(-EINVAL);
 repeat:
 	page = f2fs_grab_cache_page(NODE_MAPPING(sbi), nid, false);
 	if (!page)