[PATCH] f2fs: fix to do sanity check on i_xattr_nid in sanity_check_inode()

[Chao Yu]

syzbot reports a kernel bug as below:

F2FS-fs (loop0): Mounted with checkpoint version = 48b305e4
==================================================================
BUG: KASAN: slab-out-of-bounds in f2fs_test_bit fs/f2fs/f2fs.h:2933 [inline]
BUG: KASAN: slab-out-of-bounds in current_nat_addr fs/f2fs/node.h:213 [inline]
BUG: KASAN: slab-out-of-bounds in f2fs_get_node_info+0xece/0x1200 fs/f2fs/node.c:600
Read of size 1 at addr ffff88807a58c76c by task syz-executor280/5076

CPU: 1 PID: 5076 Comm: syz-executor280 Not tainted 6.9.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:488
 kasan_report+0x143/0x180 mm/kasan/report.c:601
 f2fs_test_bit fs/f2fs/f2fs.h:2933 [inline]
 current_nat_addr fs/f2fs/node.h:213 [inline]
 f2fs_get_node_info+0xece/0x1200 fs/f2fs/node.c:600
 f2fs_xattr_fiemap fs/f2fs/data.c:1848 [inline]
 f2fs_fiemap+0x55d/0x1ee0 fs/f2fs/data.c:1925
 ioctl_fiemap fs/ioctl.c:220 [inline]
 do_vfs_ioctl+0x1c07/0x2e50 fs/ioctl.c:838
 __do_sys_ioctl fs/ioctl.c:902 [inline]
 __se_sys_ioctl+0x81/0x170 fs/ioctl.c:890
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The root cause is we missed to do sanity check on i_xattr_nid during
f2fs_iget(), so that in fiemap() path, current_nat_addr() will access
nat_bitmap w/ offset from invalid i_xattr_nid, result in triggering
kasan bug report, fix it.

Reported-by: syzbot+3694e283cf5c40df6d14@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://lore.kernel.org/linux-f2fs-devel/00000000000094036c0616e72a1d@xxxxxxxxxx
Signed-off-by: Chao Yu <chao@xxxxxxxxxx>
---
 fs/f2fs/inode.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
index d7a5a88a1a5e..7968b14d49f4 100644
--- a/fs/f2fs/inode.c
+++ b/fs/f2fs/inode.c
@@ -362,6 +362,12 @@ static bool sanity_check_inode(struct inode *inode, struct page *node_page)
 		return false;
 	}
 
+	if (fi->i_xattr_nid && f2fs_check_nid_range(sbi, fi->i_xattr_nid)) {
+		f2fs_warn(sbi, "%s: inode (ino=%lx) has corrupted i_xattr_nid: %u, run fsck to fix.",
+			  __func__, inode->i_ino, fi->i_xattr_nid);
+		return false;
+	}
+
 	return true;
 }
 
-- 
2.40.1