+ ocfs2-invalidate-inode-if-i_mode-is-zero-after-block-read.patch added to mm-nonmm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: ocfs2: invalidate inode if i_mode is zero after block read
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     ocfs2-invalidate-inode-if-i_mode-is-zero-after-block-read.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/ocfs2-invalidate-inode-if-i_mode-is-zero-after-block-read.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Ahmet Eray Karadag <eraykrdg1@gmail.com>
Subject: ocfs2: invalidate inode if i_mode is zero after block read
Date: Wed, 3 Dec 2025 01:45:08 +0300

A panic occurs in ocfs2_unlink due to WARN_ON(inode->i_nlink == 0) when
handling a corrupted inode with i_mode=0 and i_nlink=0 in memory.

This "zombie" inode is created because ocfs2_read_locked_inode proceeds
even after ocfs2_validate_inode_block successfully validates a block that
structurally looks okay (passes checksum, signature etc.) but contains
semantically invalid data (specifically i_mode=0).  The current validation
function doesn't check for i_mode being zero.

This results in an in-memory inode with i_mode=0 being added to the VFS
cache, which later triggers the panic during unlink.

Prevent this by adding an explicit check for (i_mode == 0, i_nlink == 0,
non-orphan) within ocfs2_validate_inode_block.  If the check is true,
return -EFSCORRUPTED to signal corruption.  This causes the caller
(ocfs2_read_locked_inode) to invoke make_bad_inode(), correctly preventing
the zombie inode from entering the cache.

Link: https://lkml.kernel.org/r/20251202224507.53452-2-eraykrdg1@gmail.com
Co-developed-by: Albin Babu Varghese <albinbabuvarghese20@gmail.com>
Signed-off-by: Albin Babu Varghese <albinbabuvarghese20@gmail.com>
Signed-off-by: Ahmet Eray Karadag <eraykrdg1@gmail.com>
Reported-by: syzbot+55c40ae8a0e5f3659f2b@syzkaller.appspotmail.com
Fixes: https://syzkaller.appspot.com/bug?extid=55c40ae8a0e5f3659f2b
Link: https://lore.kernel.org/all/20251022222752.46758-2-eraykrdg1@gmail.com/T/
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: David Hunter <david.hunter.linux@gmail.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Jun Piao <piaojun@huawei.com>
Cc: Heming Zhao <heming.zhao@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/ocfs2/inode.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/fs/ocfs2/inode.c~ocfs2-invalidate-inode-if-i_mode-is-zero-after-block-read
+++ a/fs/ocfs2/inode.c
@@ -1461,6 +1461,14 @@ int ocfs2_validate_inode_block(struct su
 		goto bail;
 	}
 
+	if ((!di->i_links_count && !di->i_links_count_hi) || !di->i_mode) {
+		mlog(ML_ERROR, "Invalid dinode #%llu: "
+			"Corrupt state (nlink = %u or mode = %u) detected!\n",
+		        (unsigned long long)bh->b_blocknr,
+			ocfs2_read_links_count(di), le16_to_cpu(di->i_mode));
+		rc = -EFSCORRUPTED;
+		goto bail;
+	}
 	/*
 	 * Errors after here are fatal.
 	 */
_

Patches currently in -mm which might be from eraykrdg1@gmail.com are

ocfs2-add-ocfs2_emergency_state-helper-and-apply-to-setattr.patch
ocfs2-convert-remaining-read-only-checks-to-ocfs2_emergency_state.patch
ocfs2-invalidate-inode-if-i_mode-is-zero-after-block-read.patch