From ae2ae2b6c237d67c092f1fb6541f781e3430a392 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Mon, 11 Nov 2019 22:18:13 -0500 Subject: [PATCH] ext4: work around deleting a file with i_nlink == 0 safely [ Upstream commit c7df4a1ecb8579838ec8c56b2bb6a6716e974f37 ] If the file system is corrupted such that a file's i_links_count is too small, then it's possible that when unlinking that file, i_nlink will already be zero. Previously we were working around this kind of corruption by forcing i_nlink to one; but we were doing this before trying to delete the directory entry --- and if the file system is corrupted enough that ext4_delete_entry() fails, then we exit with i_nlink elevated, and this causes the orphan inode list handling to be FUBAR'ed, such that when we unmount the file system, the orphan inode list can get corrupted. A better way to fix this is to simply skip trying to call drop_nlink() if i_nlink is already zero, thus moving the check to the place where it makes the most sense. https://bugzilla.kernel.org/show_bug.cgi?id=205433 Link: https://lore.kernel.org/r/20191112032903.8828-1-tytso@mit.edu Signed-off-by: Theodore Ts'o Cc: stable@kernel.org Reviewed-by: Andreas Dilger Signed-off-by: Sasha Levin Signed-off-by: Lee Jones Change-Id: I9a08356694b4ef9823e9c8c417fa4a1a3fab4cdb --- fs/ext4/namei.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c index c093717d47c1..e64a38684885 100644 --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -2797,19 +2797,18 @@ static int ext4_unlink(struct inode *dir, struct dentry *dentry) if (IS_DIRSYNC(dir)) ext4_handle_sync(handle); - if (!inode->i_nlink) { - ext4_warning(inode->i_sb, - "Deleting nonexistent file (%lu), %d", - inode->i_ino, inode->i_nlink); - set_nlink(inode, 1); - } retval = ext4_delete_entry(handle, dir, de, bh); if (retval) goto end_unlink; dir->i_ctime = dir->i_mtime = ext4_current_time(dir); ext4_update_dx_flag(dir); ext4_mark_inode_dirty(handle, dir); - drop_nlink(inode); + if (!inode->i_nlink) + ext4_warning(inode->i_sb, + "Deleting nonexistent file (%lu), %d", + inode->i_ino, inode->i_nlink); + else + drop_nlink(inode); if (!inode->i_nlink) ext4_orphan_add(handle, inode); inode->i_ctime = ext4_current_time(inode);