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([2a02:4e0:2d02:fb4:3deb:c78e:540e:164e]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b76f5a2176csm1342823866b.57.2025.12.01.16.33.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 01 Dec 2025 16:33:15 -0800 (PST) From: Ahmet Eray Karadag To: mark@fasheh.com, jlbec@evilplan.org, joseph.qi@linux.alibaba.com Cc: ocfs2-devel@lists.linux.dev, linux-kernel@vger.kernel.org, david.hunter.linux@gmail.com, skhan@linuxfoundation.org, Ahmet Eray Karadag , syzbot+55c40ae8a0e5f3659f2b@syzkaller.appspotmail.com, Albin Babu Varghese Subject: [PATCH v4] ocfs2: Invalidate inode if i_mode is zero after block read Date: Tue, 2 Dec 2025 03:32:10 +0300 Message-ID: <20251202003209.188987-2-eraykrdg1@gmail.com> In-Reply-To: <20251108120133.37443-3-eraykrdg1@gmail.com> References: <20251108120133.37443-3-eraykrdg1@gmail.com> Precedence: bulk X-Mailing-List: ocfs2-devel@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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. Reported-by: syzbot+55c40ae8a0e5f3659f2b@syzkaller.appspotmail.com Fixes: https://syzkaller.appspot.com/bug?extid=55c40ae8a0e5f3659f2b Co-developed-by: Albin Babu Varghese Signed-off-by: Albin Babu Varghese Signed-off-by: Ahmet Eray Karadag Previous link: https://lore.kernel.org/all/20251022222752.46758-2-eraykrdg1@gmail.com/T/ --- v2: - Only checking either i_links_count == 0 or i_mode == 0 - Not performing le16_to_cpu() anymore - Tested with ocfs2-test --- v3: - Add checking both high and low bits of i_links_count --- v4: - Reading i_links_count hi and low bits without helper function to save few cpu cycles --- fs/ocfs2/inode.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c index 14bf440ea4df..34c2882273ae 100644 --- a/fs/ocfs2/inode.c +++ b/fs/ocfs2/inode.c @@ -1455,7 +1455,13 @@ int ocfs2_validate_inode_block(struct super_block *sb, (unsigned long long)bh->b_blocknr); goto bail; } - + if (!(di->i_links_count | di->i_links_count_hi) || !di->i_mode) { + mlog(ML_ERROR, "Invalid dinode #%llu: " + "Corrupt state (nlink=0 or mode=0,) detected!\n", + (unsigned long long)bh->b_blocknr); + rc = -EFSCORRUPTED; + goto bail; + } /* * Errors after here are fatal. */ -- 2.43.0