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From: Eric Biggers <ebiggers@kernel.org>
To: linux-fsdevel@vger.kernel.org,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, Qiujun Huang <hqjagain@gmail.com>,
	stable@vger.kernel.org,
	syzbot+a9ac3de1b5de5fb10efc@syzkaller.appspotmail.com,
	syzbot+df958cf5688a96ad3287@syzkaller.appspotmail.com
Subject: [PATCH 2/6] fs/minix: don't allow getting deleted inodes
Date: Sat, 27 Jun 2020 23:08:41 -0700
Message-ID: <20200628060846.682158-3-ebiggers@kernel.org> (raw)
In-Reply-To: <20200628060846.682158-1-ebiggers@kernel.org>

From: Eric Biggers <ebiggers@google.com>

If an inode has no links, we need to mark it bad rather than allowing it
to be accessed.  This avoids WARNINGs in inc_nlink() and drop_nlink()
when doing directory operations on a fuzzed filesystem.

Reported-by: syzbot+a9ac3de1b5de5fb10efc@syzkaller.appspotmail.com
Reported-by: syzbot+df958cf5688a96ad3287@syzkaller.appspotmail.com
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/minix/inode.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/fs/minix/inode.c b/fs/minix/inode.c
index 7cb5fd38eb14..2bca95abe8f4 100644
--- a/fs/minix/inode.c
+++ b/fs/minix/inode.c
@@ -468,6 +468,13 @@ static struct inode *V1_minix_iget(struct inode *inode)
 		iget_failed(inode);
 		return ERR_PTR(-EIO);
 	}
+	if (raw_inode->i_nlinks == 0) {
+		printk("MINIX-fs: deleted inode referenced: %lu\n",
+		       inode->i_ino);
+		brelse(bh);
+		iget_failed(inode);
+		return ERR_PTR(-ESTALE);
+	}
 	inode->i_mode = raw_inode->i_mode;
 	i_uid_write(inode, raw_inode->i_uid);
 	i_gid_write(inode, raw_inode->i_gid);
@@ -501,6 +508,13 @@ static struct inode *V2_minix_iget(struct inode *inode)
 		iget_failed(inode);
 		return ERR_PTR(-EIO);
 	}
+	if (raw_inode->i_nlinks == 0) {
+		printk("MINIX-fs: deleted inode referenced: %lu\n",
+		       inode->i_ino);
+		brelse(bh);
+		iget_failed(inode);
+		return ERR_PTR(-ESTALE);
+	}
 	inode->i_mode = raw_inode->i_mode;
 	i_uid_write(inode, raw_inode->i_uid);
 	i_gid_write(inode, raw_inode->i_gid);
-- 
2.27.0


  parent reply index

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-28  6:08 [PATCH 0/6] fs/minix: fix syzbot bugs and set s_maxbytes Eric Biggers
2020-06-28  6:08 ` [PATCH 1/6] fs/minix: check return value of sb_getblk() Eric Biggers
2020-07-07 19:26   ` Andrew Morton
2020-07-07 20:34     ` Eric Biggers
2020-06-28  6:08 ` Eric Biggers [this message]
2020-06-28  6:08 ` [PATCH 3/6] fs/minix: reject too-large maximum file size Eric Biggers
2020-06-28  6:08 ` [PATCH 4/6] fs/minix: set s_maxbytes correctly Eric Biggers
2020-06-28  6:08 ` [PATCH 5/6] fs/minix: fix block limit check for V1 filesystems Eric Biggers
2020-06-28  6:08 ` [PATCH 6/6] fs/minix: remove expected error message in block_to_path() Eric Biggers
2020-07-07 17:14 ` [PATCH 0/6] fs/minix: fix syzbot bugs and set s_maxbytes Eric Biggers

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