--- /dev/null
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2018-2024 Oracle. All Rights Reserved.
+ * Author: Darrick J. Wong <djwong@kernel.org>
+ */
+#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 "xfs_symlink_remote.h"
+#include "xfs_exchmaps.h"
+#include "xfs_exchrange.h"
+#include "xfs_health.h"
+#include "scrub/xfs_scrub.h"
+#include "scrub/scrub.h"
+#include "scrub/common.h"
+#include "scrub/trace.h"
+#include "scrub/repair.h"
+#include "scrub/tempfile.h"
+#include "scrub/tempexch.h"
+#include "scrub/reap.h"
+
+/*
+ * Symbolic Link Repair
+ * ====================
+ *
+ * We repair symbolic links by reading whatever target data we can find, up to
+ * the first NULL byte. If the recovered target strlen matches i_size, then
+ * we rewrite the target. In all other cases, we replace the target with an
+ * overly long string that cannot possibly resolve. The new target is written
+ * into a private hidden temporary file, and then a file contents exchange
+ * commits the new symlink target to the file being repaired.
+ */
+
+/* Set us up to repair the symlink file. */
+int
+xrep_setup_symlink(
+ struct xfs_scrub *sc,
+ unsigned int *resblks)
+{
+ struct xfs_mount *mp = sc->mp;
+ unsigned long long blocks;
+ int error;
+
+ error = xrep_tempfile_create(sc, S_IFLNK);
+ if (error)
+ return error;
+
+ /*
+ * If we're doing a repair, we reserve enough blocks to write out a
+ * completely new symlink file, plus twice as many blocks as we would
+ * need if we can only allocate one block per data fork mapping. This
+ * should cover the preallocation of the temporary file and exchanging
+ * the extent mappings.
+ *
+ * We cannot use xfs_exchmaps_estimate because we have not yet
+ * constructed the replacement symlink and therefore do not know how
+ * many extents it will use. By the time we do, we will have a dirty
+ * transaction (which we cannot drop because we cannot drop the
+ * symlink ILOCK) and cannot ask for more reservation.
+ */
+ blocks = xfs_symlink_blocks(sc->mp, XFS_SYMLINK_MAXLEN);
+ blocks += xfs_bmbt_calc_size(mp, blocks) * 2;
+ if (blocks > UINT_MAX)
+ return -EOPNOTSUPP;
+
+ *resblks += blocks;
+ return 0;
+}
+
+/*
+ * Try to salvage the pathname from remote blocks. Returns the number of bytes
+ * salvaged or a negative errno.
+ */
+STATIC ssize_t
+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 = 0;
+ 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 = min_t(loff_t, ip->i_disk_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;
+
+ 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;
+ }
+ return offset;
+}
+
+/*
+ * Try to salvage an inline symlink's contents. Returns the number of bytes
+ * salvaged or a negative errno.
+ */
+STATIC ssize_t
+xrep_symlink_salvage_inline(
+ struct xfs_scrub *sc)
+{
+ struct xfs_inode *ip = sc->ip;
+ char *target_buf = sc->buf;
+ char *old_target;
+ struct xfs_ifork *ifp;
+ unsigned int nr;
+
+ ifp = xfs_ifork_ptr(ip, XFS_DATA_FORK);
+ if (!ifp->if_data)
+ return 0;
+
+ /*
+ * If inode repair zapped the link target, pretend that we didn't find
+ * any bytes at all so that we can replace the (now totally lost) link
+ * target with a warning message.
+ */
+ old_target = ifp->if_data;
+ if (xfs_inode_has_sickness(sc->ip, XFS_SICK_INO_SYMLINK_ZAPPED) &&
+ sc->ip->i_disk_size == 1 && old_target[0] == '?')
+ return 0;
+
+ nr = min(XFS_SYMLINK_MAXLEN, xfs_inode_data_fork_size(ip));
+ strncpy(target_buf, ifp->if_data, nr);
+ return nr;
+}
+
+#define DUMMY_TARGET \
+ "The target of this symbolic link could not be recovered at all and " \
+ "has been replaced with this explanatory message. To avoid " \
+ "accidentally pointing to an existing file path, this message is " \
+ "longer than the maximum supported file name length. That is an " \
+ "acceptable length for a symlink target on XFS but will produce " \
+ "File Name Too Long errors if resolved."
+
+/* Salvage whatever we can of the target. */
+STATIC int
+xrep_symlink_salvage(
+ struct xfs_scrub *sc)
+{
+ char *target_buf = sc->buf;
+ ssize_t buflen = 0;
+
+ BUILD_BUG_ON(sizeof(DUMMY_TARGET) - 1 <= NAME_MAX);
+
+ /*
+ * Salvage the target if there weren't any corruption problems observed
+ * while scanning it.
+ */
+ if (!(sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)) {
+ if (sc->ip->i_df.if_format == XFS_DINODE_FMT_LOCAL)
+ buflen = xrep_symlink_salvage_inline(sc);
+ else
+ buflen = xrep_symlink_salvage_remote(sc);
+ if (buflen < 0)
+ return buflen;
+
+ /*
+ * NULL-terminate the buffer because the ondisk target does not
+ * do that for us. If salvage didn't find the exact amount of
+ * data that we expected to find, don't salvage anything.
+ */
+ target_buf[buflen] = 0;
+ if (strlen(target_buf) != sc->ip->i_disk_size)
+ buflen = 0;
+ }
+
+ /*
+ * Change an empty target into a dummy target and clear the symlink
+ * target zapped flag.
+ */
+ if (buflen == 0) {
+ sc->sick_mask |= XFS_SICK_INO_SYMLINK_ZAPPED;
+ sprintf(target_buf, DUMMY_TARGET);
+ }
+
+ trace_xrep_symlink_salvage_target(sc->ip, target_buf,
+ strlen(target_buf));
+ return 0;
+}
+
+STATIC void
+xrep_symlink_local_to_remote(
+ struct xfs_trans *tp,
+ struct xfs_buf *bp,
+ struct xfs_inode *ip,
+ struct xfs_ifork *ifp,
+ void *priv)
+{
+ struct xfs_scrub *sc = priv;
+ struct xfs_dsymlink_hdr *dsl = bp->b_addr;
+
+ xfs_symlink_local_to_remote(tp, bp, ip, ifp, NULL);
+
+ if (!xfs_has_crc(sc->mp))
+ return;
+
+ dsl->sl_owner = cpu_to_be64(sc->ip->i_ino);
+ xfs_trans_log_buf(tp, bp, 0,
+ sizeof(struct xfs_dsymlink_hdr) + ifp->if_bytes - 1);
+}
+
+/*
+ * Prepare both links' data forks for an exchange. Promote the tempfile from
+ * local format to extents format, and if the file being repaired has a short
+ * format data fork, turn it into an empty extent list.
+ */
+STATIC int
+xrep_symlink_swap_prep(
+ struct xfs_scrub *sc,
+ bool temp_local,
+ bool ip_local)
+{
+ int error;
+
+ /*
+ * If the temp link is in shortform format, convert that to a remote
+ * target so that we can use the atomic mapping exchange.
+ */
+ if (temp_local) {
+ int logflags = XFS_ILOG_CORE;
+
+ error = xfs_bmap_local_to_extents(sc->tp, sc->tempip, 1,
+ &logflags, XFS_DATA_FORK,
+ xrep_symlink_local_to_remote,
+ sc);
+ if (error)
+ return error;
+
+ xfs_trans_log_inode(sc->tp, sc->ip, 0);
+
+ error = xfs_defer_finish(&sc->tp);
+ if (error)
+ return error;
+ }
+
+ /*
+ * If the file being repaired had a shortform data fork, convert that
+ * to an empty extent list in preparation for the atomic mapping
+ * exchange.
+ */
+ if (ip_local) {
+ struct xfs_ifork *ifp;
+
+ ifp = xfs_ifork_ptr(sc->ip, XFS_DATA_FORK);
+ xfs_idestroy_fork(ifp);
+ ifp->if_format = XFS_DINODE_FMT_EXTENTS;
+ ifp->if_nextents = 0;
+ ifp->if_bytes = 0;
+ ifp->if_data = NULL;
+ ifp->if_height = 0;
+
+ xfs_trans_log_inode(sc->tp, sc->ip,
+ XFS_ILOG_CORE | XFS_ILOG_DDATA);
+ }
+
+ return 0;
+}
+
+/* Exchange the temporary symlink's data fork with the one being repaired. */
+STATIC int
+xrep_symlink_swap(
+ struct xfs_scrub *sc)
+{
+ struct xrep_tempexch *tx = sc->buf;
+ bool ip_local, temp_local;
+ int error;
+
+ ip_local = sc->ip->i_df.if_format == XFS_DINODE_FMT_LOCAL;
+ temp_local = sc->tempip->i_df.if_format == XFS_DINODE_FMT_LOCAL;
+
+ /*
+ * If the both links have a local format data fork and the rebuilt
+ * remote data would fit in the repaired file's data fork, copy the
+ * contents from the tempfile and declare ourselves done.
+ */
+ if (ip_local && temp_local &&
+ sc->tempip->i_disk_size <= xfs_inode_data_fork_size(sc->ip)) {
+ xrep_tempfile_copyout_local(sc, XFS_DATA_FORK);
+ return 0;
+ }
+
+ /* Otherwise, make sure both data forks are in block-mapping mode. */
+ error = xrep_symlink_swap_prep(sc, temp_local, ip_local);
+ if (error)
+ return error;
+
+ return xrep_tempexch_contents(sc, tx);
+}
+
+/*
+ * Free all the remote blocks and reset the data fork. The caller must join
+ * the inode to the transaction. This function returns with the inode joined
+ * to a clean scrub transaction.
+ */
+STATIC int
+xrep_symlink_reset_fork(
+ struct xfs_scrub *sc)
+{
+ struct xfs_ifork *ifp = xfs_ifork_ptr(sc->tempip, XFS_DATA_FORK);
+ int error;
+
+ /* Unmap all the remote target buffers. */
+ if (xfs_ifork_has_extents(ifp)) {
+ error = xrep_reap_ifork(sc, sc->tempip, XFS_DATA_FORK);
+ if (error)
+ return error;
+ }
+
+ trace_xrep_symlink_reset_fork(sc->tempip);
+
+ /* Reset the temp symlink target to dummy content. */
+ xfs_idestroy_fork(ifp);
+ return xfs_symlink_write_target(sc->tp, sc->tempip, sc->tempip->i_ino,
+ "?", 1, 0, 0);
+}
+
+/*
+ * Reinitialize a link target. Caller must ensure the inode is joined to
+ * the transaction.
+ */
+STATIC int
+xrep_symlink_rebuild(
+ struct xfs_scrub *sc)
+{
+ struct xrep_tempexch *tx;
+ char *target_buf = sc->buf;
+ xfs_fsblock_t fs_blocks;
+ unsigned int target_len;
+ unsigned int resblks;
+ int error;
+
+ /* How many blocks do we need? */
+ target_len = strlen(target_buf);
+ ASSERT(target_len != 0);
+ if (target_len == 0 || target_len > XFS_SYMLINK_MAXLEN)
+ return -EFSCORRUPTED;
+
+ trace_xrep_symlink_rebuild(sc->ip);
+
+ /*
+ * In preparation to write the new symlink target to the temporary
+ * file, drop the ILOCK of the file being repaired (it shouldn't be
+ * joined) and take the ILOCK of the temporary file.
+ *
+ * The VFS does not take the IOLOCK while reading a symlink (and new
+ * symlinks are hidden with INEW until they've been written) so it's
+ * possible that a readlink() could see the old corrupted contents
+ * while we're doing this.
+ */
+ xchk_iunlock(sc, XFS_ILOCK_EXCL);
+ xrep_tempfile_ilock(sc);
+ xfs_trans_ijoin(sc->tp, sc->tempip, 0);
+
+ /*
+ * Reserve resources to reinitialize the target. We're allowed to
+ * exceed file quota to repair inconsistent metadata, though this is
+ * unlikely.
+ */
+ 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->tempip, resblks, 0,
+ true);
+ if (error)
+ return error;
+
+ /* Erase the dummy target set up by the tempfile initialization. */
+ xfs_idestroy_fork(&sc->tempip->i_df);
+ sc->tempip->i_df.if_bytes = 0;
+ sc->tempip->i_df.if_format = XFS_DINODE_FMT_EXTENTS;
+
+ /* Write the salvaged target to the temporary link. */
+ error = xfs_symlink_write_target(sc->tp, sc->tempip, sc->ip->i_ino,
+ target_buf, target_len, fs_blocks, resblks);
+ if (error)
+ return error;
+
+ /*
+ * Commit the repair transaction so that we can use the atomic mapping
+ * exchange functions to compute the correct block reservations and
+ * re-lock the inodes.
+ */
+ target_buf = NULL;
+ error = xrep_trans_commit(sc);
+ if (error)
+ return error;
+
+ /* Last chance to abort before we start committing fixes. */
+ if (xchk_should_terminate(sc, &error))
+ return error;
+
+ xrep_tempfile_iunlock(sc);
+
+ /*
+ * We're done with the temporary buffer, so we can reuse it for the
+ * tempfile contents exchange information.
+ */
+ tx = sc->buf;
+ error = xrep_tempexch_trans_alloc(sc, XFS_DATA_FORK, tx);
+ if (error)
+ return error;
+
+ /*
+ * Exchange the temp link's data fork with the file being repaired.
+ * This recreates the transaction and takes the ILOCKs of the file
+ * being repaired and the temporary file.
+ */
+ error = xrep_symlink_swap(sc);
+ if (error)
+ return error;
+
+ /*
+ * Release the old symlink blocks and reset the data fork of the temp
+ * link to an empty shortform link. This is the last repair action we
+ * perform on the symlink, so we don't need to clean the transaction.
+ */
+ return xrep_symlink_reset_fork(sc);
+}
+
+/* Repair a symbolic link. */
+int
+xrep_symlink(
+ struct xfs_scrub *sc)
+{
+ int error;
+
+ /* The rmapbt is required to reap the old data fork. */
+ if (!xfs_has_rmapbt(sc->mp))
+ return -EOPNOTSUPP;
+
+ ASSERT(sc->ilock_flags & XFS_ILOCK_EXCL);
+
+ error = xrep_symlink_salvage(sc);
+ if (error)
+ return error;
+
+ /* Now reset the target. */
+ error = xrep_symlink_rebuild(sc);
+ if (error)
+ return error;
+
+ return xrep_trans_commit(sc);
+}
projects / thirdparty / kernel / linux.git / commitdiff
