1 files changed, 243 insertions, 0 deletions
diff --git a/fs/xfs/scrub/symlink_repair.c b/fs/xfs/scrub/symlink_repair.c
new file mode 100644
index 000000000000..c2040d931a2f
--- /dev/null
+++ b/fs/xfs/scrub/symlink_repair.c
@@ -0,0 +1,243 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2020 Oracle.  All Rights Reserved.
+ * Author: Darrick J. Wong <darrick.wong@oracle.com>
+ */
+#include "xfs.h"
+#include "xfs_fs.h"
+#include "xfs_shared.h"
+#include "xfs_format.h"
+#include "xfs_trans_resv.h"
+#include "xfs_mount.h"
+#include "xfs_defer.h"
+#include "xfs_btree.h"
+#include "xfs_bit.h"
+#include "xfs_log_format.h"
+#include "xfs_trans.h"
+#include "xfs_sb.h"
+#include "xfs_inode.h"
+#include "xfs_inode_fork.h"
+#include "xfs_symlink.h"
+#include "xfs_bmap.h"
+#include "xfs_quota.h"
+#include "xfs_da_format.h"
+#include "xfs_da_btree.h"
+#include "xfs_bmap_btree.h"
+#include "xfs_trans_space.h"
+#include "scrub/xfs_scrub.h"
+#include "scrub/scrub.h"
+#include "scrub/common.h"
+#include "scrub/trace.h"
+#include "scrub/repair.h"
+
+/*
+ * Symbolic Link Repair
+ * ====================
+ *
+ * There's not much we can do to repair symbolic links -- we truncate them to
+ * the first NULL byte and reinitialize the target.  Zero-length symlinks are
+ * turned into links to the current dir.
+ */
+
+/* Try to salvage the pathname from rmt blocks. */
+STATIC int
+xrep_symlink_salvage_remote(
+	struct xfs_scrub	*sc)
+{
+	struct xfs_bmbt_irec	mval[XFS_SYMLINK_MAPS];
+	struct xfs_inode	*ip = sc->ip;
+	struct xfs_buf		*bp;
+	char			*target_buf = sc->buf;
+	xfs_failaddr_t		fa;
+	xfs_filblks_t		fsblocks;
+	xfs_daddr_t		d;
+	loff_t			len;
+	loff_t			offset;
+	unsigned int		byte_cnt;
+	bool			magic_ok;
+	bool			hdr_ok;
+	int			n;
+	int			nmaps = XFS_SYMLINK_MAPS;
+	int			error;
+
+	/* We'll only read until the buffer is full. */
+	len = max_t(loff_t, ip->i_d.di_size, XFS_SYMLINK_MAXLEN);
+	fsblocks = xfs_symlink_blocks(sc->mp, len);
+	error = xfs_bmapi_read(ip, 0, fsblocks, mval, &nmaps, 0);
+	if (error)
+		return error;
+
+	offset = 0;
+	for (n = 0; n < nmaps; n++) {
+		struct xfs_dsymlink_hdr	*dsl;
+
+		d = XFS_FSB_TO_DADDR(sc->mp, mval[n].br_startblock);
+
+		/* Read the rmt block.  We'll run the verifiers manually. */
+		error = xfs_trans_read_buf(sc->mp, sc->tp, sc->mp->m_ddev_targp,
+				d, XFS_FSB_TO_BB(sc->mp, mval[n].br_blockcount),
+				0, &bp, NULL);
+		if (error)
+			return error;
+		bp->b_ops = &xfs_symlink_buf_ops;
+
+		/* How many bytes do we expect to get out of this buffer? */
+		byte_cnt = XFS_FSB_TO_B(sc->mp, mval[n].br_blockcount);
+		byte_cnt = XFS_SYMLINK_BUF_SPACE(sc->mp, byte_cnt);
+		byte_cnt = min_t(unsigned int, byte_cnt, len);
+
+		/*
+		 * See if the verifiers accept this block.  We're willing to
+		 * salvage if the if the offset/byte/ino are ok and either the
+		 * verifier passed or the magic is ok.  Anything else and we
+		 * stop dead in our tracks.
+		 */
+		fa = bp->b_ops->verify_struct(bp);
+		dsl = bp->b_addr;
+		magic_ok = dsl->sl_magic == cpu_to_be32(XFS_SYMLINK_MAGIC);
+		hdr_ok = xfs_symlink_hdr_ok(ip->i_ino, offset, byte_cnt, bp);
+		if (!hdr_ok || (fa != NULL && !magic_ok))
+			break;
+
+		memcpy(target_buf + offset, dsl + 1, byte_cnt);
+
+		len -= byte_cnt;
+		offset += byte_cnt;
+	}
+
+	/* Ensure we have a zero at the end, and /some/ contents. */
+	if (offset == 0)
+		sprintf(target_buf, ".");
+	else
+		target_buf[offset] = 0;
+	return 0;
+}
+
+/*
+ * Try to salvage an inline symlink's contents.  Empty symlinks become a link
+ * to the current directory.
+ */
+STATIC void
+xrep_symlink_salvage_inline(
+	struct xfs_scrub	*sc)
+{
+	struct xfs_inode	*ip = sc->ip;
+	struct xfs_ifork	*ifp;
+
+	ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
+	if (ifp->if_u1.if_data)
+		strncpy(sc->buf, ifp->if_u1.if_data, XFS_IFORK_DSIZE(ip));
+	if (strlen(sc->buf) == 0)
+		sprintf(sc->buf, ".");
+}
+
+/* Reset an inline symlink to its fresh configuration. */
+STATIC void
+xrep_symlink_truncate_inline(
+	struct xfs_inode	*ip)
+{
+	xfs_idestroy_fork(ip, XFS_DATA_FORK);
+	ip->i_d.di_format = XFS_DINODE_FMT_EXTENTS;
+	ip->i_d.di_nextents = 0;
+	memset(&ip->i_df, 0, sizeof(struct xfs_ifork));
+	ip->i_df.if_flags |= XFS_IFEXTENTS;
+}
+
+/*
+ * Salvage an inline symlink's contents and reset data fork.
+ * Returns with the inode joined to the transaction.
+ */
+STATIC int
+xrep_symlink_inline(
+	struct xfs_scrub	*sc)
+{
+	/* Salvage whatever link target information we can find. */
+	xrep_symlink_salvage_inline(sc);
+
+	/* Truncate the symlink. */
+	xrep_symlink_truncate_inline(sc->ip);
+
+	xfs_trans_ijoin(sc->tp, sc->ip, 0);
+	return 0;
+}
+
+/*
+ * Salvage an inline symlink's contents and reset data fork.
+ * Returns with the inode joined to the transaction.
+ */
+STATIC int
+xrep_symlink_remote(
+	struct xfs_scrub	*sc)
+{
+	int			error;
+
+	/* Salvage whatever link target information we can find. */
+	error = xrep_symlink_salvage_remote(sc);
+	if (error)
+		return error;
+
+	/* Truncate the symlink. */
+	xfs_trans_ijoin(sc->tp, sc->ip, 0);
+	return xfs_itruncate_extents(&sc->tp, sc->ip, XFS_DATA_FORK, 0);
+}
+
+/*
+ * Reinitialize a link target.  Caller must ensure the inode is joined to
+ * the transaction.
+ */
+STATIC int
+xrep_symlink_reinitialize(
+	struct xfs_scrub	*sc)
+{
+	xfs_fsblock_t		fs_blocks;
+	unsigned int		target_len;
+	uint			resblks;
+	int			error;
+
+	/* How many blocks do we need? */
+	target_len = strlen(sc->buf);
+	ASSERT(target_len != 0);
+	if (target_len == 0 || target_len > XFS_SYMLINK_MAXLEN)
+		return -EFSCORRUPTED;
+
+	/* Set up to reinitialize the target. */
+	fs_blocks = xfs_symlink_blocks(sc->mp, target_len);
+	resblks = XFS_SYMLINK_SPACE_RES(sc->mp, target_len, fs_blocks);
+	error = xfs_trans_reserve_quota_nblks(sc->tp, sc->ip, resblks, 0,
+			XFS_QMOPT_RES_REGBLKS);
+
+	/* Try to write the new target back out. */
+	error = xfs_symlink_write_target(sc->tp, sc->ip, sc->buf, target_len,
+			fs_blocks, resblks);
+	if (error)
+		return error;
+
+	/* Finish up any block mapping activities. */
+	return xfs_defer_finish(&sc->tp);
+}
+
+/* Repair a symbolic link. */
+int
+xrep_symlink(
+	struct xfs_scrub	*sc)
+{
+	struct xfs_ifork	*ifp;
+	int			error;
+
+	error = xfs_qm_dqattach_locked(sc->ip, false);
+	if (error)
+		return error;
+
+	/* Salvage whatever we can of the target. */
+	*((char *)sc->buf) = 0;
+	ifp = XFS_IFORK_PTR(sc->ip, XFS_DATA_FORK);
+	if (ifp->if_flags & XFS_IFINLINE)
+		error = xrep_symlink_inline(sc);
+	else
+		error = xrep_symlink_remote(sc);
+	if (error)
+		return error;
+
+	/* Now reset the target. */
+	return xrep_symlink_reinitialize(sc);
+}