From: Eric Biggers ebiggers@google.com Subject: fs/minix: don't allow getting deleted inodes

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.

Link: http://lkml.kernel.org/r/20200628060846.682158-3-ebiggers@kernel.org Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: syzbot+a9ac3de1b5de5fb10efc@syzkaller.appspotmail.com Reported-by: syzbot+df958cf5688a96ad3287@syzkaller.appspotmail.com Signed-off-by: Eric Biggers ebiggers@google.com Cc: Alexander Viro viro@zeniv.linux.org.uk Cc: Qiujun Huang anenbupt@gmail.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

fs/minix/inode.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)

--- a/fs/minix/inode.c~fs-minix-dont-allow-getting-deleted-inodes +++ a/fs/minix/inode.c @@ -468,6 +468,13 @@ static struct inode *V1_minix_iget(struc 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(struc 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); _