// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2008 Christoph Hellwig.
 * Portions Copyright (C) 2000-2008 Silicon Graphics, Inc.
 */

#include "xfs_platform.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_da_format.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_inode.h"
#include "xfs_da_btree.h"
#include "xfs_attr.h"
#include "xfs_acl.h"
#include "xfs_log.h"
#include "xfs_xattr.h"
#include "xfs_quota.h"

#include <linux/posix_acl_xattr.h>

/*
 * Get permission to use log-assisted atomic exchange of file extents.
 * Callers must not be running any transactions or hold any ILOCKs.
 */
static inline int
xfs_attr_grab_log_assist(
        struct xfs_mount        *mp)
{
        int                     error = 0;

        /* xattr update log intent items are already enabled */
        if (xfs_is_using_logged_xattrs(mp))
                return 0;

        /*
         * Check if the filesystem featureset is new enough to set this log
         * incompat feature bit.  Strictly speaking, the minimum requirement is
         * a V5 filesystem for the superblock field, but we'll require rmap
         * or reflink to avoid having to deal with really old kernels.
         */
        if (!xfs_has_reflink(mp) && !xfs_has_rmapbt(mp))
                return -EOPNOTSUPP;

        /* Enable log-assisted xattrs. */
        error = xfs_add_incompat_log_feature(mp,
                        XFS_SB_FEAT_INCOMPAT_LOG_XATTRS);
        if (error)
                return error;
        xfs_set_using_logged_xattrs(mp);

        xfs_warn_experimental(mp, XFS_EXPERIMENTAL_LARP);

        return 0;
}

static inline bool
xfs_attr_want_log_assist(
        struct xfs_mount        *mp)
{
#ifdef DEBUG
        /* Logged xattrs require a V5 super for log_incompat */
        return xfs_has_crc(mp) && xfs_globals.larp;
#else
        return false;
#endif
}

/*
 * Set or remove an xattr, having grabbed the appropriate logging resources
 * prior to calling libxfs.  Callers of this function are only required to
 * initialize the inode, attr_filter, name, namelen, value, and valuelen fields
 * of @args.
 */
int
xfs_attr_change(
        struct xfs_da_args      *args,
        enum xfs_attr_update    op)
{
        struct xfs_mount        *mp = args->dp->i_mount;
        int                     error;

        if (xfs_is_shutdown(mp))
                return -EIO;

        error = xfs_qm_dqattach(args->dp);
        if (error)
                return error;

        /*
         * We have no control over the attribute names that userspace passes us
         * to remove, so we have to allow the name lookup prior to attribute
         * removal to fail as well.
         */
        args->op_flags = XFS_DA_OP_OKNOENT;

        if (xfs_attr_want_log_assist(mp)) {
                error = xfs_attr_grab_log_assist(mp);
                if (error)
                        return error;

                args->op_flags |= XFS_DA_OP_LOGGED;
        }

        args->owner = args->dp->i_ino;
        args->geo = mp->m_attr_geo;
        args->whichfork = XFS_ATTR_FORK;
        xfs_attr_sethash(args);

        /*
         * Some xattrs must be resistant to allocation failure at ENOSPC, e.g.
         * creating an inode with ACLs or security attributes requires the
         * allocation of the xattr holding that information to succeed. Hence
         * we allow xattrs in the VFS TRUSTED, SYSTEM, POSIX_ACL and SECURITY
         * (LSM xattr) namespaces to dip into the reserve block pool to allow
         * manipulation of these xattrs when at ENOSPC. These VFS xattr
         * namespaces translate to the XFS_ATTR_ROOT and XFS_ATTR_SECURE on-disk
         * namespaces.
         *
         * For most of these cases, these special xattrs will fit in the inode
         * itself and so consume no extra space or only require temporary extra
         * space while an overwrite is being made. Hence the use of the reserved
         * pool is largely to avoid the worst case reservation from preventing
         * the xattr from being created at ENOSPC.
         */
        return xfs_attr_set(args, op,
                        args->attr_filter & (XFS_ATTR_ROOT | XFS_ATTR_SECURE));
}


static int
xfs_xattr_get(const struct xattr_handler *handler, struct dentry *unused,
                struct inode *inode, const char *name, void *value, size_t size)
{
        struct xfs_da_args      args = {
                .dp             = XFS_I(inode),
                .attr_filter    = handler->flags,
                .name           = name,
                .namelen        = strlen(name),
                .value          = value,
                .valuelen       = size,
        };
        int                     error;

        if (xfs_ifork_zapped(XFS_I(inode), XFS_ATTR_FORK))
                return -EIO;

        error = xfs_attr_get(&args);
        if (error)
                return error;
        return args.valuelen;
}

static inline enum xfs_attr_update
xfs_xattr_flags_to_op(
        int             flags,
        const void      *value)
{
        if (!value)
                return XFS_ATTRUPDATE_REMOVE;
        if (flags & XATTR_CREATE)
                return XFS_ATTRUPDATE_CREATE;
        if (flags & XATTR_REPLACE)
                return XFS_ATTRUPDATE_REPLACE;
        return XFS_ATTRUPDATE_UPSERT;
}

static int
xfs_xattr_set(const struct xattr_handler *handler,
              struct mnt_idmap *idmap, struct dentry *unused,
              struct inode *inode, const char *name, const void *value,
              size_t size, int flags)
{
        struct xfs_da_args      args = {
                .dp             = XFS_I(inode),
                .attr_filter    = handler->flags,
                .name           = name,
                .namelen        = strlen(name),
                .value          = (void *)value,
                .valuelen       = size,
        };
        int                     error;

        error = xfs_attr_change(&args, xfs_xattr_flags_to_op(flags, value));
        if (!error && (handler->flags & XFS_ATTR_ROOT))
                xfs_forget_acl(inode, name);
        return error;
}

static const struct xattr_handler xfs_xattr_user_handler = {
        .prefix = XATTR_USER_PREFIX,
        .flags  = 0, /* no flags implies user namespace */
        .get    = xfs_xattr_get,
        .set    = xfs_xattr_set,
};

static const struct xattr_handler xfs_xattr_trusted_handler = {
        .prefix = XATTR_TRUSTED_PREFIX,
        .flags  = XFS_ATTR_ROOT,
        .get    = xfs_xattr_get,
        .set    = xfs_xattr_set,
};

static const struct xattr_handler xfs_xattr_security_handler = {
        .prefix = XATTR_SECURITY_PREFIX,
        .flags  = XFS_ATTR_SECURE,
        .get    = xfs_xattr_get,
        .set    = xfs_xattr_set,
};

const struct xattr_handler * const xfs_xattr_handlers[] = {
        &xfs_xattr_user_handler,
        &xfs_xattr_trusted_handler,
        &xfs_xattr_security_handler,
        NULL
};

static void
__xfs_xattr_put_listent(
        struct xfs_attr_list_context *context,
        char *prefix,
        int prefix_len,
        unsigned char *name,
        int namelen)
{
        char *offset;
        int arraytop;

        if (context->count < 0 || context->seen_enough)
                return;

        if (!context->buffer)
                goto compute_size;

        arraytop = context->count + prefix_len + namelen + 1;
        if (arraytop > context->firstu) {
                context->count = -1;    /* insufficient space */
                context->seen_enough = 1;
                return;
        }
        offset = context->buffer + context->count;
        memcpy(offset, prefix, prefix_len);
        offset += prefix_len;
        memcpy(offset, (char *)name, namelen);                  /* real name */
        offset += namelen;
        *offset = '\0';

compute_size:
        context->count += prefix_len + namelen + 1;
        return;
}

static void
xfs_xattr_put_listent(
        struct xfs_attr_list_context *context,
        int             flags,
        unsigned char   *name,
        int             namelen,
        void            *value,
        int             valuelen)
{
        char *prefix;
        int prefix_len;

        ASSERT(context->count >= 0);

        /* Don't expose private xattr namespaces. */
        if (flags & XFS_ATTR_PRIVATE_NSP_MASK)
                return;

        if (flags & XFS_ATTR_ROOT) {
#ifdef CONFIG_XFS_POSIX_ACL
                if (namelen == SGI_ACL_FILE_SIZE &&
                    strncmp(name, SGI_ACL_FILE,
                            SGI_ACL_FILE_SIZE) == 0) {
                        __xfs_xattr_put_listent(
                                        context, XATTR_SYSTEM_PREFIX,
                                        XATTR_SYSTEM_PREFIX_LEN,
                                        XATTR_POSIX_ACL_ACCESS,
                                        strlen(XATTR_POSIX_ACL_ACCESS));
                } else if (namelen == SGI_ACL_DEFAULT_SIZE &&
                         strncmp(name, SGI_ACL_DEFAULT,
                                 SGI_ACL_DEFAULT_SIZE) == 0) {
                        __xfs_xattr_put_listent(
                                        context, XATTR_SYSTEM_PREFIX,
                                        XATTR_SYSTEM_PREFIX_LEN,
                                        XATTR_POSIX_ACL_DEFAULT,
                                        strlen(XATTR_POSIX_ACL_DEFAULT));
                }
#endif

                /*
                 * Only show root namespace entries if we are actually allowed to
                 * see them.
                 */
                if (!capable(CAP_SYS_ADMIN))
                        return;

                prefix = XATTR_TRUSTED_PREFIX;
                prefix_len = XATTR_TRUSTED_PREFIX_LEN;
        } else if (flags & XFS_ATTR_SECURE) {
                prefix = XATTR_SECURITY_PREFIX;
                prefix_len = XATTR_SECURITY_PREFIX_LEN;
        } else {
                prefix = XATTR_USER_PREFIX;
                prefix_len = XATTR_USER_PREFIX_LEN;
        }

        __xfs_xattr_put_listent(context, prefix, prefix_len, name,
                                namelen);
        return;
}

ssize_t
xfs_vn_listxattr(
        struct dentry   *dentry,
        char            *data,
        size_t          size)
{
        struct xfs_attr_list_context context;
        struct inode    *inode = d_inode(dentry);
        int             error;

        if (xfs_ifork_zapped(XFS_I(inode), XFS_ATTR_FORK))
                return -EIO;

        /*
         * First read the regular on-disk attributes.
         */
        memset(&context, 0, sizeof(context));
        context.dp = XFS_I(inode);
        context.resynch = 1;
        context.bufsize = size;
        context.buffer = size ? data : NULL;
        context.firstu = context.bufsize;
        context.put_listent = xfs_xattr_put_listent;

        error = xfs_attr_list(&context);
        if (error)
                return error;
        if (context.count < 0)
                return -ERANGE;

        return context.count;
}