nilfs2 updates for v7.2

- nilfs2: Fix return in nilfs_mkdir
 - nilfs2: fix backing_dev_info reference leak
 - nilfs2: reject CLEAN_SEGMENTS ioctl with out-of-range segment numbers
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Merge tag 'nilfs2-v7.2-tag1' of git://git.kernel.org/pub/scm/linux/kernel/git/vdubeyko/nilfs2

Pull nilfs2 updates from Viacheslav Dubeyko:
 "Fixes of syzbot reported issue and various small fixes in NILFS2
  functionality.

   - fix hung task in nilfs_transaction_begin() (Deepanshu Kartikey)

     Reported by syzbot. The root cause is that user-supplied segment
     numbers were not validated before nilfs_clean_segments() began
     doing work; the range check on each segnum was performed deep
     inside the call chain by nilfs_sufile_updatev(), which emits a
     nilfs_warn() per invalid entry while still holding the segctor lock
     and the sufile mi_sem.

     Fix it by validating the contents of kbufs[4] in
     nilfs_clean_segments() immediately after acquiring ns_segctor_sem
     via nilfs_transaction_lock().

   - fix a smatch warning in nilfs_mkdir() warn (Hongling Zeng)

     This corrects a semantic issue related to the use of the
     ERR_PTR macro that arose from a recent VFS change.

   - fix a backing_dev_info reference leak (Shuangpeng Bai)

     setup_bdev_super() initializes sb->s_bdev and takes a reference on
     the block device backing_dev_info when assigning sb->s_bdi.

     nilfs_fill_super() takes another reference to the same
     backing_dev_info and stores it in sb->s_bdi again. The extra
     reference is not paired with a matching bdi_put(), since
     generic_shutdown_super() releases sb->s_bdi only once.

     Drop the redundant bdi_get() in nilfs_fill_super(). The single
     reference taken by setup_bdev_super() is enough and is released
     during superblock shutdown"

* tag 'nilfs2-v7.2-tag1' of git://git.kernel.org/pub/scm/linux/kernel/git/vdubeyko/nilfs2:
  nilfs2: Fix return in nilfs_mkdir
  nilfs2: fix backing_dev_info reference leak
  nilfs2: reject CLEAN_SEGMENTS ioctl with out-of-range segment numbers

fs/nilfs2/namei.c

@@ -258,7 +258,7 @@ static struct dentry *nilfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 	else
 		nilfs_transaction_abort(dir->i_sb);
 
-	return ERR_PTR(err);
+	return err ? ERR_PTR(err) : NULL;
 
 out_fail:
 	drop_nlink(inode);

fs/nilfs2/segment.c

@@ -2512,12 +2512,33 @@ int nilfs_clean_segments(struct super_block *sb, struct nilfs_argv *argv,
 	struct nilfs_sc_info *sci = nilfs->ns_writer;
 	struct nilfs_transaction_info ti;
 	int err;
+	size_t i, nfreesegs = argv[4].v_nmembs;
+	__u64 *segnumv = kbufs[4];
 
 	if (unlikely(!sci))
 		return -EROFS;
 
 	nilfs_transaction_lock(sb, &ti, 1);
 
+	/*
+	 * Validate segment numbers under ns_segctor_sem (held for write
+	 * by nilfs_transaction_lock above) so the check is serialized
+	 * against nilfs_ioctl_resize(), which can modify ns_nsegments.
+	 * Rejecting bad input here, before any segment-cleaning work
+	 * begins, avoids the per-element diagnostic path inside
+	 * nilfs_sufile_updatev() that would otherwise run under this
+	 * same lock and stall concurrent readers.
+	 */
+	for (i = 0; i < nfreesegs; i++) {
+		if (segnumv[i] >= nilfs->ns_nsegments) {
+			nilfs_err(sb,
+				 "Segment number %llu to be freed is out of range",
+				 (unsigned long long)segnumv[i]);
+			err = -EINVAL;
+			goto bail_unlock;
+		}
+	}
+
 	err = nilfs_mdt_save_to_shadow_map(nilfs->ns_dat);
 	if (unlikely(err))
 		goto out_unlock;
@@ -2558,6 +2579,7 @@ int nilfs_clean_segments(struct super_block *sb, struct nilfs_argv *argv,
 	sci->sc_freesegs = NULL;
 	sci->sc_nfreesegs = 0;
 	nilfs_mdt_clear_shadow_map(nilfs->ns_dat);
+ bail_unlock:
 	nilfs_transaction_unlock(sb);
 	return err;
 }

fs/nilfs2/super.c

@@ -1070,8 +1070,6 @@ nilfs_fill_super(struct super_block *sb, struct fs_context *fc)
 	sb->s_time_gran = 1;
 	sb->s_max_links = NILFS_LINK_MAX;
 
-	sb->s_bdi = bdi_get(sb->s_bdev->bd_disk->bdi);
-
 	err = load_nilfs(nilfs, sb);
 	if (err)
 		goto failed_nilfs;