[PATCH] ntfs3: fix NULL pointer dereference in 'ni_write_inode'

[Ye Bin]

From: Ye Bin <yebin10@xxxxxxxxxx>

Syzbot found the following issue:
Unable to handle kernel NULL pointer dereference at virtual address 0000000000000016
Mem abort info:
  ESR = 0x0000000096000006
  EC = 0x25: DABT (current EL), IL = 32 bits
  SET = 0, FnV = 0
  EA = 0, S1PTW = 0
  FSC = 0x06: level 2 translation fault
Data abort info:
  ISV = 0, ISS = 0x00000006
  CM = 0, WnR = 0
user pgtable: 4k pages, 48-bit VAs, pgdp=000000010af56000
[0000000000000016] pgd=08000001090da003, p4d=08000001090da003, pud=08000001090ce003, pmd=0000000000000000
Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 PID: 3036 Comm: syz-executor206 Not tainted 6.0.0-rc6-syzkaller-17739-g16c9f284e746 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2022
pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : is_rec_inuse fs/ntfs3/ntfs.h:313 [inline]
pc : ni_write_inode+0xac/0x798 fs/ntfs3/frecord.c:3232
lr : ni_write_inode+0xa0/0x798 fs/ntfs3/frecord.c:3226
sp : ffff8000126c3800
x29: ffff8000126c3860 x28: 0000000000000000 x27: ffff0000c8b02000
x26: ffff0000c7502320 x25: ffff0000c7502288 x24: 0000000000000000
x23: ffff80000cbec91c x22: ffff0000c8b03000 x21: ffff0000c8b02000
x20: 0000000000000001 x19: ffff0000c75024d8 x18: 00000000000000c0
x17: ffff80000dd1b198 x16: ffff80000db59158 x15: ffff0000c4b6b500
x14: 00000000000000b8 x13: 0000000000000000 x12: ffff0000c4b6b500
x11: ff80800008be1b60 x10: 0000000000000000 x9 : ffff0000c4b6b500
x8 : 0000000000000000 x7 : ffff800008be1b50 x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000001 x3 : 0000000000000000
x2 : 0000000000000008 x1 : 0000000000000001 x0 : 0000000000000000
Call trace:
 is_rec_inuse fs/ntfs3/ntfs.h:313 [inline]
 ni_write_inode+0xac/0x798 fs/ntfs3/frecord.c:3232
 ntfs_evict_inode+0x54/0x84 fs/ntfs3/inode.c:1744
 evict+0xec/0x334 fs/inode.c:665
 iput_final fs/inode.c:1748 [inline]
 iput+0x2c4/0x324 fs/inode.c:1774
 ntfs_new_inode+0x7c/0xe0 fs/ntfs3/fsntfs.c:1660
 ntfs_create_inode+0x20c/0xe78 fs/ntfs3/inode.c:1278
 ntfs_create+0x54/0x74 fs/ntfs3/namei.c:100
 lookup_open fs/namei.c:3413 [inline]
 open_last_lookups fs/namei.c:3481 [inline]
 path_openat+0x804/0x11c4 fs/namei.c:3688
 do_filp_open+0xdc/0x1b8 fs/namei.c:3718
 do_sys_openat2+0xb8/0x22c fs/open.c:1311
 do_sys_open fs/open.c:1327 [inline]
 __do_sys_openat fs/open.c:1343 [inline]
 __se_sys_openat fs/open.c:1338 [inline]
 __arm64_sys_openat+0xb0/0xe0 fs/open.c:1338
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall arch/arm64/kernel/syscall.c:52 [inline]
 el0_svc_common+0x138/0x220 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x48/0x164 arch/arm64/kernel/syscall.c:206
 el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:636
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:654
 el0t_64_sync+0x18c/0x190
Code: 97dafee4 340001b4 f9401328 2a1f03e0 (79402d14)
---[ end trace 0000000000000000 ]---

Above issue may happens as follows:
ntfs_new_inode
  mi_init
    mi->mrec = kmalloc(sbi->record_size, GFP_NOFS); -->failed to allocate memory
      if (!mi->mrec)
        return -ENOMEM;
iput
  iput_final
    evict
      ntfs_evict_inode
        ni_write_inode
	  is_rec_inuse(ni->mi.mrec)-> As 'ni->mi.mrec' is NULL trigger NULL-ptr-deref

To solve above issue if new inode failed make inode bad before call 'iput()' in
'ntfs_new_inode()'.

Reported-by: syzbot+f45957555ed4a808cc7a@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Ye Bin <yebin10@xxxxxxxxxx>
---
 fs/ntfs3/fsntfs.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/ntfs3/fsntfs.c b/fs/ntfs3/fsntfs.c
index 567563771bf8..8de861ddec60 100644
--- a/fs/ntfs3/fsntfs.c
+++ b/fs/ntfs3/fsntfs.c
@@ -1683,6 +1683,7 @@ struct ntfs_inode *ntfs_new_inode(struct ntfs_sb_info *sbi, CLST rno, bool dir)
 
 out:
 	if (err) {
+		make_bad_inode(inode);
 		iput(inode);
 		ni = ERR_PTR(err);
 	}
-- 
2.31.1