f2fs: fix to do sanity check on direct node in truncate_dnode()

commit a6ec837 upstream.

syzbot reports below bug:

BUG: KASAN: slab-use-after-free in f2fs_truncate_data_blocks_range+0x122a/0x14c0 fs/f2fs/file.c:574
Read of size 4 at addr ffff88802a25c000 by task syz-executor148/5000

CPU: 1 PID: 5000 Comm: syz-executor148 Not tainted 6.4.0-rc7-syzkaller-00041-ge660abd551f1 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd9/0x150 lib/dump_stack.c:106
 print_address_description.constprop.0+0x2c/0x3c0 mm/kasan/report.c:351
 print_report mm/kasan/report.c:462 [inline]
 kasan_report+0x11c/0x130 mm/kasan/report.c:572
 f2fs_truncate_data_blocks_range+0x122a/0x14c0 fs/f2fs/file.c:574
 truncate_dnode+0x229/0x2e0 fs/f2fs/node.c:944
 f2fs_truncate_inode_blocks+0x64b/0xde0 fs/f2fs/node.c:1154
 f2fs_do_truncate_blocks+0x4ac/0xf30 fs/f2fs/file.c:721
 f2fs_truncate_blocks+0x7b/0x300 fs/f2fs/file.c:749
 f2fs_truncate.part.0+0x4a5/0x630 fs/f2fs/file.c:799
 f2fs_truncate include/linux/fs.h:825 [inline]
 f2fs_setattr+0x1738/0x2090 fs/f2fs/file.c:1006
 notify_change+0xb2c/0x1180 fs/attr.c:483
 do_truncate+0x143/0x200 fs/open.c:66
 handle_truncate fs/namei.c:3295 [inline]
 do_open fs/namei.c:3640 [inline]
 path_openat+0x2083/0x2750 fs/namei.c:3791
 do_filp_open+0x1ba/0x410 fs/namei.c:3818
 do_sys_openat2+0x16d/0x4c0 fs/open.c:1356
 do_sys_open fs/open.c:1372 [inline]
 __do_sys_creat fs/open.c:1448 [inline]
 __se_sys_creat fs/open.c:1442 [inline]
 __x64_sys_creat+0xcd/0x120 fs/open.c:1442
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

The root cause is, inodeA references inodeB via inodeB's ino, once inodeA
is truncated, it calls truncate_dnode() to truncate data blocks in inodeB's
node page, it traverse mapping data from node->i.i_addr[0] to
node->i.i_addr[ADDRS_PER_BLOCK() - 1], result in out-of-boundary access.

This patch fixes to add sanity check on dnode page in truncate_dnode(),
so that, it can help to avoid triggering such issue, and once it encounters
such issue, it will record newly introduced ERROR_INVALID_NODE_REFERENCE
error into superblock, later fsck can detect such issue and try repairing.

Also, it removes f2fs_truncate_data_blocks() for cleanup due to the
function has only one caller, and uses f2fs_truncate_data_blocks_range()
instead.

Reported-and-tested-by: syzbot+12cb4425b22169b52036@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/linux-f2fs-devel/000000000000f3038a05fef867f8@google.com
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/f2fs/f2fs.h

@@ -3431,7 +3431,6 @@ static inline bool __is_valid_data_blkaddr(block_t blkaddr)
  * file.c
  */
 int f2fs_sync_file(struct file *file, loff_t start, loff_t end, int datasync);
-void f2fs_truncate_data_blocks(struct dnode_of_data *dn);
 int f2fs_do_truncate_blocks(struct inode *inode, u64 from, bool lock);
 int f2fs_truncate_blocks(struct inode *inode, u64 from, bool lock);
 int f2fs_truncate(struct inode *inode);

fs/f2fs/file.c

@@ -628,11 +628,6 @@ void f2fs_truncate_data_blocks_range(struct dnode_of_data *dn, int count)
 					 dn->ofs_in_node, nr_free);
 }
 
-void f2fs_truncate_data_blocks(struct dnode_of_data *dn)
-{
-	f2fs_truncate_data_blocks_range(dn, ADDRS_PER_BLOCK(dn->inode));
-}
-
 static int truncate_partial_data_page(struct inode *inode, u64 from,
 								bool cache_only)
 {

fs/f2fs/node.c

@@ -923,23 +923,33 @@ static int truncate_node(struct dnode_of_data *dn)
 
 static int truncate_dnode(struct dnode_of_data *dn)
 {
+	struct f2fs_sb_info *sbi = F2FS_I_SB(dn->inode);
 	struct page *page;
 	int err;
 
 	if (dn->nid == 0)
 		return 1;
 
 	/* get direct node */
-	page = f2fs_get_node_page(F2FS_I_SB(dn->inode), dn->nid);
+	page = f2fs_get_node_page(sbi, dn->nid);
 	if (PTR_ERR(page) == -ENOENT)
 		return 1;
 	else if (IS_ERR(page))
 		return PTR_ERR(page);
 
+	if (IS_INODE(page) || ino_of_node(page) != dn->inode->i_ino) {
+		f2fs_err(sbi, "incorrect node reference, ino: %lu, nid: %u, ino_of_node: %u",
+				dn->inode->i_ino, dn->nid, ino_of_node(page));
+		set_sbi_flag(sbi, SBI_NEED_FSCK);
+		f2fs_handle_error(sbi, ERROR_INVALID_NODE_REFERENCE);
+		f2fs_put_page(page, 1);
+		return -EFSCORRUPTED;
+	}
+
 	/* Make dnode_of_data for parameter */
 	dn->node_page = page;
 	dn->ofs_in_node = 0;
-	f2fs_truncate_data_blocks(dn);
+	f2fs_truncate_data_blocks_range(dn, ADDRS_PER_BLOCK(dn->inode));
 	err = truncate_node(dn);
 	if (err) {
 		f2fs_put_page(page, 1);

include/linux/f2fs_fs.h

@@ -104,6 +104,7 @@ enum f2fs_error {
 	ERROR_INCONSISTENT_SIT,
 	ERROR_CORRUPTED_VERITY_XATTR,
 	ERROR_CORRUPTED_XATTR,
+	ERROR_INVALID_NODE_REFERENCE,
 	ERROR_MAX,
 };