diff options
Diffstat (limited to 'fs/xfs/scrub/symlink_repair.c')
| -rw-r--r-- | fs/xfs/scrub/symlink_repair.c | 509 |
1 files changed, 509 insertions, 0 deletions
diff --git a/fs/xfs/scrub/symlink_repair.c b/fs/xfs/scrub/symlink_repair.c new file mode 100644 index 0000000000..d015a86ef4 --- /dev/null +++ b/fs/xfs/scrub/symlink_repair.c @@ -0,0 +1,509 @@ +// 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; + /* We require atomic file exchange range to rebuild anything. */ + if (!xfs_has_exchange_range(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); +} |