Merge tag 'inode-repair-improvements-6.10_2024-04-15' of...

Merge tag 'inode-repair-improvements-6.10_2024-04-15' of https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux into xfs-6.10-mergeA

xfs: inode-related repair fixes

While doing QA of the online fsck code, I made a few observations:
First, nobody was checking that the di_onlink field is actually zero;
Second, that allocating a temporary file for repairs can fail (and
thus bring down the entire fs) if the inode cluster is corrupt; and
Third, that file link counts do not pin at ~0U to prevent integer
overflows.  Fourth, the x{chk,rep}_metadata_inode_fork functions
should be subclassing the main scrub context, not modifying the
parent's setup willy-nilly.

This scattered patchset fixes those three problems.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

* tag 'inode-repair-improvements-6.10_2024-04-15' of https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux:
  xfs: create subordinate scrub contexts for xchk_metadata_inode_subtype
  xfs: pin inodes that would otherwise overflow link count
  xfs: try to avoid allocating from sick inode clusters
  xfs: check unused nlink fields in the ondisk inode

fs/xfs/libxfs/xfs_format.h

@@ -899,6 +899,12 @@ static inline uint xfs_dinode_size(int version)
  */
 #define	XFS_MAXLINK		((1U << 31) - 1U)
 
+/*
+ * Any file that hits the maximum ondisk link count should be pinned to avoid
+ * a use-after-free situation.
+ */
+#define	XFS_NLINK_PINNED	(~0U)
+
 /*
  * Values for di_format
  *

fs/xfs/libxfs/xfs_ialloc.c

@@ -1057,6 +1057,33 @@ xfs_inobt_first_free_inode(
 	return xfs_lowbit64(realfree);
 }
 
+/*
+ * If this AG has corrupt inodes, check if allocating this inode would fail
+ * with corruption errors.  Returns 0 if we're clear, or EAGAIN to try again
+ * somewhere else.
+ */
+static int
+xfs_dialloc_check_ino(
+	struct xfs_perag	*pag,
+	struct xfs_trans	*tp,
+	xfs_ino_t		ino)
+{
+	struct xfs_imap		imap;
+	struct xfs_buf		*bp;
+	int			error;
+
+	error = xfs_imap(pag, tp, ino, &imap, 0);
+	if (error)
+		return -EAGAIN;
+
+	error = xfs_imap_to_bp(pag->pag_mount, tp, &imap, &bp);
+	if (error)
+		return -EAGAIN;
+
+	xfs_trans_brelse(tp, bp);
+	return 0;
+}
+
 /*
  * Allocate an inode using the inobt-only algorithm.
  */
@@ -1309,6 +1336,13 @@ xfs_dialloc_ag_inobt(
 	ASSERT((XFS_AGINO_TO_OFFSET(mp, rec.ir_startino) %
 				   XFS_INODES_PER_CHUNK) == 0);
 	ino = XFS_AGINO_TO_INO(mp, pag->pag_agno, rec.ir_startino + offset);
+
+	if (xfs_ag_has_sickness(pag, XFS_SICK_AG_INODES)) {
+		error = xfs_dialloc_check_ino(pag, tp, ino);
+		if (error)
+			goto error0;
+	}
+
 	rec.ir_free &= ~XFS_INOBT_MASK(offset);
 	rec.ir_freecount--;
 	error = xfs_inobt_update(cur, &rec);
@@ -1584,6 +1618,12 @@ xfs_dialloc_ag(
 				   XFS_INODES_PER_CHUNK) == 0);
 	ino = XFS_AGINO_TO_INO(mp, pag->pag_agno, rec.ir_startino + offset);
 
+	if (xfs_ag_has_sickness(pag, XFS_SICK_AG_INODES)) {
+		error = xfs_dialloc_check_ino(pag, tp, ino);
+		if (error)
+			goto error_cur;
+	}
+
 	/*
 	 * Modify or remove the finobt record.
 	 */

fs/xfs/libxfs/xfs_inode_buf.c

@@ -491,6 +491,14 @@ xfs_dinode_verify(
 			return __this_address;
 	}
 
+	if (dip->di_version > 1) {
+		if (dip->di_onlink)
+			return __this_address;
+	} else {
+		if (dip->di_nlink)
+			return __this_address;
+	}
+
 	/* don't allow invalid i_size */
 	di_size = be64_to_cpu(dip->di_size);
 	if (di_size & (1ULL << 63))

fs/xfs/scrub/common.c

@@ -1203,27 +1203,12 @@ xchk_metadata_inode_subtype(
 	struct xfs_scrub	*sc,
 	unsigned int		scrub_type)
 {
-	__u32			smtype = sc->sm->sm_type;
-	unsigned int		sick_mask = sc->sick_mask;
+	struct xfs_scrub_subord	*sub;
 	int			error;
 
-	sc->sm->sm_type = scrub_type;
-
-	switch (scrub_type) {
-	case XFS_SCRUB_TYPE_INODE:
-		error = xchk_inode(sc);
-		break;
-	case XFS_SCRUB_TYPE_BMBTD:
-		error = xchk_bmap_data(sc);
-		break;
-	default:
-		ASSERT(0);
-		error = -EFSCORRUPTED;
-		break;
-	}
-
-	sc->sick_mask = sick_mask;
-	sc->sm->sm_type = smtype;
+	sub = xchk_scrub_create_subord(sc, scrub_type);
+	error = sub->sc.ops->scrub(&sub->sc);
+	xchk_scrub_free_subord(sub);
 	return error;
 }
 

fs/xfs/scrub/dir_repair.c

@@ -1145,7 +1145,9 @@ xrep_dir_set_nlink(
 	struct xfs_scrub	*sc = rd->sc;
 	struct xfs_inode	*dp = sc->ip;
 	struct xfs_perag	*pag;
-	unsigned int		new_nlink = rd->subdirs + 2;
+	unsigned int		new_nlink = min_t(unsigned long long,
+						  rd->subdirs + 2,
+						  XFS_NLINK_PINNED);
 	int			error;
 
 	/*
@@ -1201,13 +1203,6 @@ xrep_dir_swap(
 	bool			ip_local, temp_local;
 	int			error = 0;
 
-	/*
-	 * If we found enough subdirs to overflow this directory's link count,
-	 * bail out to userspace before we modify anything.
-	 */
-	if (rd->subdirs + 2 > XFS_MAXLINK)
-		return -EFSCORRUPTED;
-
 	/*
 	 * If we never found the parent for this directory, temporarily assign
 	 * the root dir as the parent; we'll move this to the orphanage after

fs/xfs/scrub/inode_repair.c

@@ -516,6 +516,17 @@ xrep_dinode_mode(
 	return 0;
 }
 
+/* Fix unused link count fields having nonzero values. */
+STATIC void
+xrep_dinode_nlinks(
+	struct xfs_dinode	*dip)
+{
+	if (dip->di_version > 1)
+		dip->di_onlink = 0;
+	else
+		dip->di_nlink = 0;
+}
+
 /* Fix any conflicting flags that the verifiers complain about. */
 STATIC void
 xrep_dinode_flags(
@@ -1377,6 +1388,7 @@ xrep_dinode_core(
 	iget_error = xrep_dinode_mode(ri, dip);
 	if (iget_error)
 		goto write;
+	xrep_dinode_nlinks(dip);
 	xrep_dinode_flags(sc, dip, ri->rt_extents > 0);
 	xrep_dinode_size(ri, dip);
 	xrep_dinode_extsize_hints(sc, dip);

fs/xfs/scrub/nlinks.c

@@ -607,9 +607,11 @@ xchk_nlinks_compare_inode(
 	 * this as a corruption.  The VFS won't let users increase the link
 	 * count, but it will let them decrease it.
 	 */
-	if (total_links > XFS_MAXLINK) {
+	if (total_links > XFS_NLINK_PINNED) {
 		xchk_ino_set_corrupt(sc, ip->i_ino);
 		goto out_corrupt;
+	} else if (total_links > XFS_MAXLINK) {
+		xchk_ino_set_warning(sc, ip->i_ino);
 	}
 
 	/* Link counts should match. */

fs/xfs/scrub/nlinks_repair.c

@@ -238,14 +238,10 @@ xrep_nlinks_repair_inode(
 
 	/* Commit the new link count if it changed. */
 	if (total_links != actual_nlink) {
-		if (total_links > XFS_MAXLINK) {
-			trace_xrep_nlinks_unfixable_inode(mp, ip, &obs);
-			goto out_trans;
-		}
-
 		trace_xrep_nlinks_update_inode(mp, ip, &obs);
 
-		set_nlink(VFS_I(ip), total_links);
+		set_nlink(VFS_I(ip), min_t(unsigned long long, total_links,
+					   XFS_NLINK_PINNED));
 		dirty = true;
 	}
 

fs/xfs/scrub/repair.c

@@ -1009,55 +1009,27 @@ xrep_metadata_inode_subtype(
 	struct xfs_scrub	*sc,
 	unsigned int		scrub_type)
 {
-	__u32			smtype = sc->sm->sm_type;
-	__u32			smflags = sc->sm->sm_flags;
-	unsigned int		sick_mask = sc->sick_mask;
+	struct xfs_scrub_subord	*sub;
 	int			error;
 
 	/*
-	 * Let's see if the inode needs repair.  We're going to open-code calls
-	 * to the scrub and repair functions so that we can hang on to the
+	 * Let's see if the inode needs repair.  Use a subordinate scrub context
+	 * to call the scrub and repair functions so that we can hang on to the
 	 * resources that we already acquired instead of using the standard
 	 * setup/teardown routines.
 	 */
-	sc->sm->sm_flags &= ~XFS_SCRUB_FLAGS_OUT;
-	sc->sm->sm_type = scrub_type;
-
-	switch (scrub_type) {
-	case XFS_SCRUB_TYPE_INODE:
-		error = xchk_inode(sc);
-		break;
-	case XFS_SCRUB_TYPE_BMBTD:
-		error = xchk_bmap_data(sc);
-		break;
-	case XFS_SCRUB_TYPE_BMBTA:
-		error = xchk_bmap_attr(sc);
-		break;
-	default:
-		ASSERT(0);
-		error = -EFSCORRUPTED;
-	}
+	sub = xchk_scrub_create_subord(sc, scrub_type);
+	error = sub->sc.ops->scrub(&sub->sc);
 	if (error)
 		goto out;
-
-	if (!xrep_will_attempt(sc))
+	if (!xrep_will_attempt(&sub->sc))
 		goto out;
 
 	/*
 	 * Repair some part of the inode.  This will potentially join the inode
 	 * to the transaction.
 	 */
-	switch (scrub_type) {
-	case XFS_SCRUB_TYPE_INODE:
-		error = xrep_inode(sc);
-		break;
-	case XFS_SCRUB_TYPE_BMBTD:
-		error = xrep_bmap(sc, XFS_DATA_FORK, false);
-		break;
-	case XFS_SCRUB_TYPE_BMBTA:
-		error = xrep_bmap(sc, XFS_ATTR_FORK, false);
-		break;
-	}
+	error = sub->sc.ops->repair(&sub->sc);
 	if (error)
 		goto out;
 
@@ -1066,10 +1038,10 @@ xrep_metadata_inode_subtype(
 	 * that the inode will not be joined to the transaction when we exit
 	 * the function.
 	 */
-	error = xfs_defer_finish(&sc->tp);
+	error = xfs_defer_finish(&sub->sc.tp);
 	if (error)
 		goto out;
-	error = xfs_trans_roll(&sc->tp);
+	error = xfs_trans_roll(&sub->sc.tp);
 	if (error)
 		goto out;
 
@@ -1077,31 +1049,18 @@ xrep_metadata_inode_subtype(
 	 * Clear the corruption flags and re-check the metadata that we just
 	 * repaired.
 	 */
-	sc->sm->sm_flags &= ~XFS_SCRUB_FLAGS_OUT;
-
-	switch (scrub_type) {
-	case XFS_SCRUB_TYPE_INODE:
-		error = xchk_inode(sc);
-		break;
-	case XFS_SCRUB_TYPE_BMBTD:
-		error = xchk_bmap_data(sc);
-		break;
-	case XFS_SCRUB_TYPE_BMBTA:
-		error = xchk_bmap_attr(sc);
-		break;
-	}
+	sub->sc.sm->sm_flags &= ~XFS_SCRUB_FLAGS_OUT;
+	error = sub->sc.ops->scrub(&sub->sc);
 	if (error)
 		goto out;
 
 	/* If corruption persists, the repair has failed. */
-	if (xchk_needs_repair(sc->sm)) {
+	if (xchk_needs_repair(sub->sc.sm)) {
 		error = -EFSCORRUPTED;
 		goto out;
 	}
 out:
-	sc->sick_mask = sick_mask;
-	sc->sm->sm_type = smtype;
-	sc->sm->sm_flags = smflags;
+	xchk_scrub_free_subord(sub);
 	return error;
 }
 

fs/xfs/scrub/scrub.c

@@ -177,6 +177,39 @@ xchk_fsgates_disable(
 }
 #undef FSGATES_MASK
 
+/* Free the resources associated with a scrub subtype. */
+void
+xchk_scrub_free_subord(
+	struct xfs_scrub_subord	*sub)
+{
+	struct xfs_scrub	*sc = sub->parent_sc;
+
+	ASSERT(sc->ip == sub->sc.ip);
+	ASSERT(sc->orphanage == sub->sc.orphanage);
+	ASSERT(sc->tempip == sub->sc.tempip);
+
+	sc->sm->sm_type = sub->old_smtype;
+	sc->sm->sm_flags = sub->old_smflags |
+				(sc->sm->sm_flags & XFS_SCRUB_FLAGS_OUT);
+	sc->tp = sub->sc.tp;
+
+	if (sub->sc.buf) {
+		if (sub->sc.buf_cleanup)
+			sub->sc.buf_cleanup(sub->sc.buf);
+		kvfree(sub->sc.buf);
+	}
+	if (sub->sc.xmbtp)
+		xmbuf_free(sub->sc.xmbtp);
+	if (sub->sc.xfile)
+		xfile_destroy(sub->sc.xfile);
+
+	sc->ilock_flags = sub->sc.ilock_flags;
+	sc->orphanage_ilock_flags = sub->sc.orphanage_ilock_flags;
+	sc->temp_ilock_flags = sub->sc.temp_ilock_flags;
+
+	kfree(sub);
+}
+
 /* Free all the resources and finish the transactions. */
 STATIC int
 xchk_teardown(
@@ -505,6 +538,36 @@ static inline void xchk_postmortem(struct xfs_scrub *sc)
 }
 #endif /* CONFIG_XFS_ONLINE_REPAIR */
 
+/*
+ * Create a new scrub context from an existing one, but with a different scrub
+ * type.
+ */
+struct xfs_scrub_subord *
+xchk_scrub_create_subord(
+	struct xfs_scrub	*sc,
+	unsigned int		subtype)
+{
+	struct xfs_scrub_subord	*sub;
+
+	sub = kzalloc(sizeof(*sub), XCHK_GFP_FLAGS);
+	if (!sub)
+		return ERR_PTR(-ENOMEM);
+
+	sub->old_smtype = sc->sm->sm_type;
+	sub->old_smflags = sc->sm->sm_flags;
+	sub->parent_sc = sc;
+	memcpy(&sub->sc, sc, sizeof(struct xfs_scrub));
+	sub->sc.ops = &meta_scrub_ops[subtype];
+	sub->sc.sm->sm_type = subtype;
+	sub->sc.sm->sm_flags &= ~XFS_SCRUB_FLAGS_OUT;
+	sub->sc.buf = NULL;
+	sub->sc.buf_cleanup = NULL;
+	sub->sc.xfile = NULL;
+	sub->sc.xmbtp = NULL;
+
+	return sub;
+}
+
 /* Dispatch metadata scrubbing. */
 int
 xfs_scrub_metadata(

fs/xfs/scrub/scrub.h

@@ -156,6 +156,17 @@ struct xfs_scrub {
  */
 #define XREP_FSGATES_ALL	(XREP_FSGATES_EXCHANGE_RANGE)
 
+struct xfs_scrub_subord {
+	struct xfs_scrub	sc;
+	struct xfs_scrub	*parent_sc;
+	unsigned int		old_smtype;
+	unsigned int		old_smflags;
+};
+
+struct xfs_scrub_subord *xchk_scrub_create_subord(struct xfs_scrub *sc,
+		unsigned int subtype);
+void xchk_scrub_free_subord(struct xfs_scrub_subord *sub);
+
 /* Metadata scrubbers */
 int xchk_tester(struct xfs_scrub *sc);
 int xchk_superblock(struct xfs_scrub *sc);

fs/xfs/xfs_inode.c

@@ -890,22 +890,25 @@ xfs_init_new_inode(
  */
 static int			/* error */
 xfs_droplink(
-	xfs_trans_t *tp,
-	xfs_inode_t *ip)
+	struct xfs_trans	*tp,
+	struct xfs_inode	*ip)
 {
-	if (VFS_I(ip)->i_nlink == 0) {
-		xfs_alert(ip->i_mount,
-			  "%s: Attempt to drop inode (%llu) with nlink zero.",
-			  __func__, ip->i_ino);
-		return -EFSCORRUPTED;
-	}
+	struct inode		*inode = VFS_I(ip);
 
 	xfs_trans_ichgtime(tp, ip, XFS_ICHGTIME_CHG);
 
-	drop_nlink(VFS_I(ip));
+	if (inode->i_nlink == 0) {
+		xfs_info_ratelimited(tp->t_mountp,
+ "Inode 0x%llx link count dropped below zero.  Pinning link count.",
+				ip->i_ino);
+		set_nlink(inode, XFS_NLINK_PINNED);
+	}
+	if (inode->i_nlink != XFS_NLINK_PINNED)
+		drop_nlink(inode);
+
 	xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
 
-	if (VFS_I(ip)->i_nlink)
+	if (inode->i_nlink)
 		return 0;
 
 	return xfs_iunlink(tp, ip);
@@ -919,9 +922,17 @@ xfs_bumplink(
 	struct xfs_trans	*tp,
 	struct xfs_inode	*ip)
 {
+	struct inode		*inode = VFS_I(ip);
+
 	xfs_trans_ichgtime(tp, ip, XFS_ICHGTIME_CHG);
 
-	inc_nlink(VFS_I(ip));
+	if (inode->i_nlink == XFS_NLINK_PINNED - 1)
+		xfs_info_ratelimited(tp->t_mountp,
+ "Inode 0x%llx link count exceeded maximum.  Pinning link count.",
+				ip->i_ino);
+	if (inode->i_nlink != XFS_NLINK_PINNED)
+		inc_nlink(inode);
+
 	xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
 }