// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2000-2006 Silicon Graphics, Inc.
 * Copyright (c) 2012-2013 Red Hat, Inc.
 * All rights reserved.
 */
#include "xfs_platform.h"
#include "xfs_shared.h"
#include "xfs_fs.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_bit.h"
#include "xfs_mount.h"
#include "xfs_dir2.h"
#include "xfs_inode.h"
#include "xfs_bmap.h"
#include "xfs_bmap_btree.h"
#include "xfs_quota.h"
#include "xfs_symlink.h"
#include "xfs_trans_space.h"
#include "xfs_trace.h"
#include "xfs_trans.h"
#include "xfs_ialloc.h"
#include "xfs_error.h"
#include "xfs_health.h"
#include "xfs_symlink_remote.h"
#include "xfs_parent.h"
#include "xfs_defer.h"

int
xfs_readlink(
        struct xfs_inode        *ip,
        char                    *link)
{
        struct xfs_mount        *mp = ip->i_mount;
        xfs_fsize_t             pathlen;
        int                     error;

        trace_xfs_readlink(ip);

        if (xfs_is_shutdown(mp))
                return -EIO;
        if (xfs_ifork_zapped(ip, XFS_DATA_FORK))
                return -EIO;

        xfs_ilock(ip, XFS_ILOCK_SHARED);

        pathlen = ip->i_disk_size;
        if (!pathlen)
                goto out_corrupt;

        if (pathlen < 0 || pathlen > XFS_SYMLINK_MAXLEN) {
                xfs_alert(mp, "%s: inode (%llu) bad symlink length (%lld)",
                         __func__, (unsigned long long) ip->i_ino,
                         (long long) pathlen);
                ASSERT(0);
                goto out_corrupt;
        }

        if (ip->i_df.if_format == XFS_DINODE_FMT_LOCAL) {
                /*
                 * The VFS crashes on a NULL pointer, so return -EFSCORRUPTED
                 * if if_data is junk.
                 */
                if (XFS_IS_CORRUPT(ip->i_mount, !ip->i_df.if_data))
                        goto out_corrupt;

                memcpy(link, ip->i_df.if_data, pathlen + 1);
                error = 0;
        } else {
                error = xfs_symlink_remote_read(ip, link);
        }

        xfs_iunlock(ip, XFS_ILOCK_SHARED);
        return error;
 out_corrupt:
        xfs_iunlock(ip, XFS_ILOCK_SHARED);
        xfs_inode_mark_sick(ip, XFS_SICK_INO_SYMLINK);
        return -EFSCORRUPTED;
}

int
xfs_symlink(
        struct mnt_idmap        *idmap,
        struct xfs_inode        *dp,
        struct xfs_name         *link_name,
        const char              *target_path,
        umode_t                 mode,
        struct xfs_inode        **ipp)
{
        struct xfs_mount        *mp = dp->i_mount;
        struct xfs_icreate_args args = {
                .idmap          = idmap,
                .pip            = dp,
                .mode           = S_IFLNK | (mode & ~S_IFMT),
        };
        struct xfs_dir_update   du = {
                .dp             = dp,
                .name           = link_name,
        };
        struct xfs_trans        *tp = NULL;
        int                     error = 0;
        int                     pathlen;
        bool                    unlock_dp_on_error = false;
        xfs_filblks_t           fs_blocks;
        struct xfs_dquot        *udqp;
        struct xfs_dquot        *gdqp;
        struct xfs_dquot        *pdqp;
        uint                    resblks;
        xfs_ino_t               ino;

        *ipp = NULL;

        trace_xfs_symlink(dp, link_name);

        if (xfs_is_shutdown(mp))
                return -EIO;

        /*
         * Check component lengths of the target path name.
         */
        pathlen = strlen(target_path);
        if (pathlen >= XFS_SYMLINK_MAXLEN)      /* total string too long */
                return -ENAMETOOLONG;
        ASSERT(pathlen > 0);

        /* Make sure that we have allocated dquot(s) on disk. */
        error = xfs_icreate_dqalloc(&args, &udqp, &gdqp, &pdqp);
        if (error)
                return error;

        /*
         * The symlink will fit into the inode data fork?
         * If there are no parent pointers, then there wont't be any attributes.
         * So we get the whole variable part, and do not need to reserve extra
         * blocks.  Otherwise, we need to reserve the blocks.
         */
        if (pathlen <= XFS_LITINO(mp) && !xfs_has_parent(mp))
                fs_blocks = 0;
        else
                fs_blocks = xfs_symlink_blocks(mp, pathlen);
        resblks = xfs_symlink_space_res(mp, link_name->len, fs_blocks);

        error = xfs_parent_start(mp, &du.ppargs);
        if (error)
                goto out_release_dquots;

        error = xfs_trans_alloc_icreate(mp, &M_RES(mp)->tr_symlink, udqp, gdqp,
                        pdqp, resblks, &tp);
        if (error)
                goto out_parent;

        xfs_ilock(dp, XFS_ILOCK_EXCL | XFS_ILOCK_PARENT);
        unlock_dp_on_error = true;

        /*
         * Check whether the directory allows new symlinks or not.
         */
        if (dp->i_diflags & XFS_DIFLAG_NOSYMLINKS) {
                error = -EPERM;
                goto out_trans_cancel;
        }

        /*
         * Allocate an inode for the symlink.
         */
        error = xfs_dialloc(&tp, &args, &ino);
        if (!error)
                error = xfs_icreate(tp, ino, &args, &du.ip);
        if (error)
                goto out_trans_cancel;

        /*
         * Now we join the directory inode to the transaction.  We do not do it
         * earlier because xfs_dir_ialloc might commit the previous transaction
         * (and release all the locks).  An error from here on will result in
         * the transaction cancel unlocking dp so don't do it explicitly in the
         * error path.
         */
        xfs_trans_ijoin(tp, dp, 0);

        /*
         * Also attach the dquot(s) to it, if applicable.
         */
        xfs_qm_vop_create_dqattach(tp, du.ip, udqp, gdqp, pdqp);

        resblks -= XFS_IALLOC_SPACE_RES(mp);
        error = xfs_symlink_write_target(tp, du.ip, du.ip->i_ino, target_path,
                        pathlen, fs_blocks, resblks);
        if (error)
                goto out_trans_cancel;
        resblks -= fs_blocks;
        i_size_write(VFS_I(du.ip), du.ip->i_disk_size);

        /*
         * Create the directory entry for the symlink.
         */
        error = xfs_dir_create_child(tp, resblks, &du);
        if (error)
                goto out_trans_cancel;

        /*
         * If this is a synchronous mount, make sure that the
         * symlink transaction goes to disk before returning to
         * the user.
         */
        if (xfs_has_wsync(mp) || xfs_has_dirsync(mp))
                xfs_trans_set_sync(tp);

        error = xfs_trans_commit(tp);
        if (error)
                goto out_release_inode;

        xfs_qm_dqrele(udqp);
        xfs_qm_dqrele(gdqp);
        xfs_qm_dqrele(pdqp);

        *ipp = du.ip;
        xfs_iunlock(du.ip, XFS_ILOCK_EXCL);
        xfs_iunlock(dp, XFS_ILOCK_EXCL);
        xfs_parent_finish(mp, du.ppargs);
        return 0;

out_trans_cancel:
        xfs_trans_cancel(tp);
out_release_inode:
        /*
         * Wait until after the current transaction is aborted to finish the
         * setup of the inode and release the inode.  This prevents recursive
         * transactions and deadlocks from xfs_inactive.
         */
        if (du.ip) {
                xfs_iunlock(du.ip, XFS_ILOCK_EXCL);
                xfs_finish_inode_setup(du.ip);
                xfs_irele(du.ip);
        }
out_parent:
        xfs_parent_finish(mp, du.ppargs);
out_release_dquots:
        xfs_qm_dqrele(udqp);
        xfs_qm_dqrele(gdqp);
        xfs_qm_dqrele(pdqp);

        if (unlock_dp_on_error)
                xfs_iunlock(dp, XFS_ILOCK_EXCL);
        return error;
}

/*
 * Free a symlink that has blocks associated with it.
 *
 * Note: zero length symlinks are not allowed to exist. When we set the size to
 * zero, also change it to a regular file so that it does not get written to
 * disk as a zero length symlink. The inode is on the unlinked list already, so
 * userspace cannot find this inode anymore, so this change is not user visible
 * but allows us to catch corrupt zero-length symlinks in the verifiers.
 */
STATIC int
xfs_inactive_symlink_rmt(
        struct xfs_inode        *ip)
{
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_trans        *tp;
        int                     error;

        ASSERT(!xfs_need_iread_extents(&ip->i_df));
        /*
         * We're freeing a symlink that has some
         * blocks allocated to it.  Free the
         * blocks here.  We know that we've got
         * either 1 or 2 extents and that we can
         * free them all in one bunmapi call.
         */
        ASSERT(ip->i_df.if_nextents > 0 && ip->i_df.if_nextents <= 2);

        error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, 0, 0, 0, &tp);
        if (error)
                return error;

        xfs_ilock(ip, XFS_ILOCK_EXCL);
        xfs_trans_ijoin(tp, ip, 0);

        /*
         * Lock the inode, fix the size, turn it into a regular file and join it
         * to the transaction.  Hold it so in the normal path, we still have it
         * locked for the second transaction.  In the error paths we need it
         * held so the cancel won't rele it, see below.
         */
        ip->i_disk_size = 0;
        VFS_I(ip)->i_mode = (VFS_I(ip)->i_mode & ~S_IFMT) | S_IFREG;
        xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);

        error = xfs_symlink_remote_truncate(tp, ip);
        if (error)
                goto error_trans_cancel;

        error = xfs_trans_commit(tp);
        if (error) {
                ASSERT(xfs_is_shutdown(mp));
                goto error_unlock;
        }

        /*
         * Remove the memory for extent descriptions (just bookkeeping).
         */
        if (ip->i_df.if_bytes)
                xfs_idata_realloc(ip, -ip->i_df.if_bytes, XFS_DATA_FORK);
        ASSERT(ip->i_df.if_bytes == 0);

        xfs_iunlock(ip, XFS_ILOCK_EXCL);
        return 0;

error_trans_cancel:
        xfs_trans_cancel(tp);
error_unlock:
        xfs_iunlock(ip, XFS_ILOCK_EXCL);
        return error;
}

/*
 * xfs_inactive_symlink - free a symlink
 */
int
xfs_inactive_symlink(
        struct xfs_inode        *ip)
{
        struct xfs_mount        *mp = ip->i_mount;
        int                     pathlen;

        trace_xfs_inactive_symlink(ip);

        if (xfs_is_shutdown(mp))
                return -EIO;

        xfs_ilock(ip, XFS_ILOCK_EXCL);
        pathlen = (int)ip->i_disk_size;
        ASSERT(pathlen);

        if (pathlen <= 0 || pathlen > XFS_SYMLINK_MAXLEN) {
                xfs_alert(mp, "%s: inode (0x%llx) bad symlink length (%d)",
                         __func__, (unsigned long long)ip->i_ino, pathlen);
                xfs_iunlock(ip, XFS_ILOCK_EXCL);
                ASSERT(0);
                xfs_inode_mark_sick(ip, XFS_SICK_INO_SYMLINK);
                return -EFSCORRUPTED;
        }

        /*
         * Inline fork state gets removed by xfs_difree() so we have nothing to
         * do here in that case.
         */
        if (ip->i_df.if_format == XFS_DINODE_FMT_LOCAL) {
                xfs_iunlock(ip, XFS_ILOCK_EXCL);
                return 0;
        }

        xfs_iunlock(ip, XFS_ILOCK_EXCL);

        /* remove the remote symlink */
        return xfs_inactive_symlink_rmt(ip);
}