]> git.ipfire.org Git - thirdparty/kernel/linux.git/commitdiff
ovl: refactor ovl_lookup()
authorChristian Brauner <brauner@kernel.org>
Mon, 17 Nov 2025 09:34:08 +0000 (10:34 +0100)
committerChristian Brauner <brauner@kernel.org>
Wed, 19 Nov 2025 20:58:25 +0000 (21:58 +0100)
Split the core into a separate helper in preparation of converting the
caller to the scoped ovl cred guard.

Link: https://patch.msgid.link/20251117-work-ovl-cred-guard-v4-37-b31603935724@kernel.org
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
fs/overlayfs/namei.c

index 49874525cf52b36dfd75655d3339f9c8f1c8af0c..5bed42c079f0c0c2fb44de9e10a43ea8d1f75ec3 100644 (file)
@@ -1070,57 +1070,44 @@ static bool ovl_check_follow_redirect(struct ovl_lookup_data *d)
        return true;
 }
 
-struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
-                         unsigned int flags)
+struct ovl_lookup_ctx {
+       struct dentry *dentry;
+       struct ovl_entry *oe;
+       struct ovl_path *stack;
+       struct ovl_path *origin_path;
+       struct dentry *upperdentry;
+       struct dentry *index;
+       struct inode *inode;
+       unsigned int ctr;
+};
+
+static int ovl_lookup_layers(struct ovl_lookup_ctx *ctx, struct ovl_lookup_data *d)
 {
-       struct ovl_entry *oe = NULL;
-       const struct cred *old_cred;
+       struct dentry *dentry = ctx->dentry;
        struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
        struct ovl_entry *poe = OVL_E(dentry->d_parent);
        struct ovl_entry *roe = OVL_E(dentry->d_sb->s_root);
-       struct ovl_path *stack = NULL, *origin_path = NULL;
-       struct dentry *upperdir, *upperdentry = NULL;
-       struct dentry *origin = NULL;
-       struct dentry *index = NULL;
-       unsigned int ctr = 0;
-       struct inode *inode = NULL;
-       bool upperopaque = false;
        bool check_redirect = (ovl_redirect_follow(ofs) || ofs->numdatalayer);
+       struct dentry *upperdir;
        struct dentry *this;
-       unsigned int i;
-       int err;
+       struct dentry *origin = NULL;
+       bool upperopaque = false;
        bool uppermetacopy = false;
        int metacopy_size = 0;
-       struct ovl_lookup_data d = {
-               .sb = dentry->d_sb,
-               .dentry = dentry,
-               .name = dentry->d_name,
-               .is_dir = false,
-               .opaque = false,
-               .stop = false,
-               .last = check_redirect ? false : !ovl_numlower(poe),
-               .redirect = NULL,
-               .upperredirect = NULL,
-               .metacopy = 0,
-       };
-
-       if (dentry->d_name.len > ofs->namelen)
-               return ERR_PTR(-ENAMETOOLONG);
+       unsigned int i;
+       int err;
 
-       old_cred = ovl_override_creds(dentry->d_sb);
        upperdir = ovl_dentry_upper(dentry->d_parent);
        if (upperdir) {
-               d.layer = &ofs->layers[0];
-               err = ovl_lookup_layer(upperdir, &d, &upperdentry, true);
+               d->layer = &ofs->layers[0];
+               err = ovl_lookup_layer(upperdir, d, &ctx->upperdentry, true);
                if (err)
-                       goto out;
+                       return err;
 
-               if (upperdentry && upperdentry->d_flags & DCACHE_OP_REAL) {
-                       dput(upperdentry);
-                       err = -EREMOTE;
-                       goto out;
-               }
-               if (upperdentry && !d.is_dir) {
+               if (ctx->upperdentry && ctx->upperdentry->d_flags & DCACHE_OP_REAL)
+                       return -EREMOTE;
+
+               if (ctx->upperdentry && !d->is_dir) {
                        /*
                         * Lookup copy up origin by decoding origin file handle.
                         * We may get a disconnected dentry, which is fine,
@@ -1131,50 +1118,50 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
                         * number - it's the same as if we held a reference
                         * to a dentry in lower layer that was moved under us.
                         */
-                       err = ovl_check_origin(ofs, upperdentry, &origin_path);
+                       err = ovl_check_origin(ofs, ctx->upperdentry, &ctx->origin_path);
                        if (err)
-                               goto out_put_upper;
+                               return err;
 
-                       if (d.metacopy)
+                       if (d->metacopy)
                                uppermetacopy = true;
-                       metacopy_size = d.metacopy;
+                       metacopy_size = d->metacopy;
                }
 
-               if (d.redirect) {
+               if (d->redirect) {
                        err = -ENOMEM;
-                       d.upperredirect = kstrdup(d.redirect, GFP_KERNEL);
-                       if (!d.upperredirect)
-                               goto out_put_upper;
-                       if (d.redirect[0] == '/')
+                       d->upperredirect = kstrdup(d->redirect, GFP_KERNEL);
+                       if (!d->upperredirect)
+                               return err;
+                       if (d->redirect[0] == '/')
                                poe = roe;
                }
-               upperopaque = d.opaque;
+               upperopaque = d->opaque;
        }
 
-       if (!d.stop && ovl_numlower(poe)) {
+       if (!d->stop && ovl_numlower(poe)) {
                err = -ENOMEM;
-               stack = ovl_stack_alloc(ofs->numlayer - 1);
-               if (!stack)
-                       goto out_put_upper;
+               ctx->stack = ovl_stack_alloc(ofs->numlayer - 1);
+               if (!ctx->stack)
+                       return err;
        }
 
-       for (i = 0; !d.stop && i < ovl_numlower(poe); i++) {
+       for (i = 0; !d->stop && i < ovl_numlower(poe); i++) {
                struct ovl_path lower = ovl_lowerstack(poe)[i];
 
-               if (!ovl_check_follow_redirect(&d)) {
+               if (!ovl_check_follow_redirect(d)) {
                        err = -EPERM;
-                       goto out_put;
+                       return err;
                }
 
                if (!check_redirect)
-                       d.last = i == ovl_numlower(poe) - 1;
-               else if (d.is_dir || !ofs->numdatalayer)
-                       d.last = lower.layer->idx == ovl_numlower(roe);
+                       d->last = i == ovl_numlower(poe) - 1;
+               else if (d->is_dir || !ofs->numdatalayer)
+                       d->last = lower.layer->idx == ovl_numlower(roe);
 
-               d.layer = lower.layer;
-               err = ovl_lookup_layer(lower.dentry, &d, &this, false);
+               d->layer = lower.layer;
+               err = ovl_lookup_layer(lower.dentry, d, &this, false);
                if (err)
-                       goto out_put;
+                       return err;
 
                if (!this)
                        continue;
@@ -1183,11 +1170,11 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
                 * If no origin fh is stored in upper of a merge dir, store fh
                 * of lower dir and set upper parent "impure".
                 */
-               if (upperdentry && !ctr && !ofs->noxattr && d.is_dir) {
-                       err = ovl_fix_origin(ofs, dentry, this, upperdentry);
+               if (ctx->upperdentry && !ctx->ctr && !ofs->noxattr && d->is_dir) {
+                       err = ovl_fix_origin(ofs, dentry, this, ctx->upperdentry);
                        if (err) {
                                dput(this);
-                               goto out_put;
+                               return err;
                        }
                }
 
@@ -1200,23 +1187,23 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
                 * matches the dentry found using path based lookup,
                 * otherwise error out.
                 */
-               if (upperdentry && !ctr &&
-                   ((d.is_dir && ovl_verify_lower(dentry->d_sb)) ||
-                    (!d.is_dir && ofs->config.index && origin_path))) {
-                       err = ovl_verify_origin(ofs, upperdentry, this, false);
+               if (ctx->upperdentry && !ctx->ctr &&
+                   ((d->is_dir && ovl_verify_lower(dentry->d_sb)) ||
+                    (!d->is_dir && ofs->config.index && ctx->origin_path))) {
+                       err = ovl_verify_origin(ofs, ctx->upperdentry, this, false);
                        if (err) {
                                dput(this);
-                               if (d.is_dir)
+                               if (d->is_dir)
                                        break;
-                               goto out_put;
+                               return err;
                        }
                        origin = this;
                }
 
-               if (!upperdentry && !d.is_dir && !ctr && d.metacopy)
-                       metacopy_size = d.metacopy;
+               if (!ctx->upperdentry && !d->is_dir && !ctx->ctr && d->metacopy)
+                       metacopy_size = d->metacopy;
 
-               if (d.metacopy && ctr) {
+               if (d->metacopy && ctx->ctr) {
                        /*
                         * Do not store intermediate metacopy dentries in
                         * lower chain, except top most lower metacopy dentry.
@@ -1226,15 +1213,15 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
                        dput(this);
                        this = NULL;
                } else {
-                       stack[ctr].dentry = this;
-                       stack[ctr].layer = lower.layer;
-                       ctr++;
+                       ctx->stack[ctx->ctr].dentry = this;
+                       ctx->stack[ctx->ctr].layer = lower.layer;
+                       ctx->ctr++;
                }
 
-               if (d.stop)
+               if (d->stop)
                        break;
 
-               if (d.redirect && d.redirect[0] == '/' && poe != roe) {
+               if (d->redirect && d->redirect[0] == '/' && poe != roe) {
                        poe = roe;
                        /* Find the current layer on the root dentry */
                        i = lower.layer->idx - 1;
@@ -1245,12 +1232,12 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
         * Defer lookup of lowerdata in data-only layers to first access.
         * Don't require redirect=follow and metacopy=on in this case.
         */
-       if (d.metacopy && ctr && ofs->numdatalayer && d.absolute_redirect) {
-               d.metacopy = 0;
-               ctr++;
-       } else if (!ovl_check_follow_redirect(&d)) {
+       if (d->metacopy && ctx->ctr && ofs->numdatalayer && d->absolute_redirect) {
+               d->metacopy = 0;
+               ctx->ctr++;
+       } else if (!ovl_check_follow_redirect(d)) {
                err = -EPERM;
-               goto out_put;
+               return err;
        }
 
        /*
@@ -1261,20 +1248,20 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
         * For metacopy dentry, path based lookup will find lower dentries.
         * Just make sure a corresponding data dentry has been found.
         */
-       if (d.metacopy || (uppermetacopy && !ctr)) {
+       if (d->metacopy || (uppermetacopy && !ctx->ctr)) {
                pr_warn_ratelimited("metacopy with no lower data found - abort lookup (%pd2)\n",
                                    dentry);
                err = -EIO;
-               goto out_put;
-       } else if (!d.is_dir && upperdentry && !ctr && origin_path) {
-               if (WARN_ON(stack != NULL)) {
+               return err;
+       } else if (!d->is_dir && ctx->upperdentry && !ctx->ctr && ctx->origin_path) {
+               if (WARN_ON(ctx->stack != NULL)) {
                        err = -EIO;
-                       goto out_put;
+                       return err;
                }
-               stack = origin_path;
-               ctr = 1;
-               origin = origin_path->dentry;
-               origin_path = NULL;
+               ctx->stack = ctx->origin_path;
+               ctx->ctr = 1;
+               origin = ctx->origin_path->dentry;
+               ctx->origin_path = NULL;
        }
 
        /*
@@ -1296,38 +1283,39 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
         * is enabled and if upper had an ORIGIN xattr.
         *
         */
-       if (!upperdentry && ctr)
-               origin = stack[0].dentry;
+       if (!ctx->upperdentry && ctx->ctr)
+               origin = ctx->stack[0].dentry;
 
        if (origin && ovl_indexdir(dentry->d_sb) &&
-           (!d.is_dir || ovl_index_all(dentry->d_sb))) {
-               index = ovl_lookup_index(ofs, upperdentry, origin, true);
-               if (IS_ERR(index)) {
-                       err = PTR_ERR(index);
-                       index = NULL;
-                       goto out_put;
+           (!d->is_dir || ovl_index_all(dentry->d_sb))) {
+               ctx->index = ovl_lookup_index(ofs, ctx->upperdentry, origin, true);
+               if (IS_ERR(ctx->index)) {
+                       err = PTR_ERR(ctx->index);
+                       ctx->index = NULL;
+                       return err;
                }
        }
 
-       if (ctr) {
-               oe = ovl_alloc_entry(ctr);
+       if (ctx->ctr) {
+               ctx->oe = ovl_alloc_entry(ctx->ctr);
                err = -ENOMEM;
-               if (!oe)
-                       goto out_put;
+               if (!ctx->oe)
+                       return err;
 
-               ovl_stack_cpy(ovl_lowerstack(oe), stack, ctr);
+               ovl_stack_cpy(ovl_lowerstack(ctx->oe), ctx->stack, ctx->ctr);
        }
 
        if (upperopaque)
                ovl_dentry_set_opaque(dentry);
-       if (d.xwhiteouts)
+       if (d->xwhiteouts)
                ovl_dentry_set_xwhiteouts(dentry);
 
-       if (upperdentry)
+       if (ctx->upperdentry)
                ovl_dentry_set_upper_alias(dentry);
-       else if (index) {
+       else if (ctx->index) {
+               char *upperredirect;
                struct path upperpath = {
-                       .dentry = upperdentry = dget(index),
+                       .dentry = ctx->upperdentry = dget(ctx->index),
                        .mnt = ovl_upper_mnt(ofs),
                };
 
@@ -1336,77 +1324,97 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
                 * assignment happens only if upperdentry is non-NULL, and
                 * this one only if upperdentry is NULL.
                 */
-               d.upperredirect = ovl_get_redirect_xattr(ofs, &upperpath, 0);
-               if (IS_ERR(d.upperredirect)) {
-                       err = PTR_ERR(d.upperredirect);
-                       d.upperredirect = NULL;
-                       goto out_free_oe;
-               }
+               upperredirect = ovl_get_redirect_xattr(ofs, &upperpath, 0);
+               if (IS_ERR(upperredirect))
+                       return PTR_ERR(upperredirect);
+               d->upperredirect = upperredirect;
 
                err = ovl_check_metacopy_xattr(ofs, &upperpath, NULL);
                if (err < 0)
-                       goto out_free_oe;
-               d.metacopy = uppermetacopy = err;
+                       return err;
+               d->metacopy = uppermetacopy = err;
                metacopy_size = err;
 
-               if (!ovl_check_follow_redirect(&d)) {
+               if (!ovl_check_follow_redirect(d)) {
                        err = -EPERM;
-                       goto out_free_oe;
+                       return err;
                }
        }
 
-       if (upperdentry || ctr) {
+       if (ctx->upperdentry || ctx->ctr) {
+               struct inode *inode;
                struct ovl_inode_params oip = {
-                       .upperdentry = upperdentry,
-                       .oe = oe,
-                       .index = index,
-                       .redirect = d.upperredirect,
+                       .upperdentry = ctx->upperdentry,
+                       .oe = ctx->oe,
+                       .index = ctx->index,
+                       .redirect = d->upperredirect,
                };
 
                /* Store lowerdata redirect for lazy lookup */
-               if (ctr > 1 && !d.is_dir && !stack[ctr - 1].dentry) {
-                       oip.lowerdata_redirect = d.redirect;
-                       d.redirect = NULL;
+               if (ctx->ctr > 1 && !d->is_dir && !ctx->stack[ctx->ctr - 1].dentry) {
+                       oip.lowerdata_redirect = d->redirect;
+                       d->redirect = NULL;
                }
+
                inode = ovl_get_inode(dentry->d_sb, &oip);
-               err = PTR_ERR(inode);
                if (IS_ERR(inode))
-                       goto out_free_oe;
-               if (upperdentry && !uppermetacopy)
-                       ovl_set_flag(OVL_UPPERDATA, inode);
+                       return PTR_ERR(inode);
+
+               ctx->inode = inode;
+               if (ctx->upperdentry && !uppermetacopy)
+                       ovl_set_flag(OVL_UPPERDATA, ctx->inode);
 
                if (metacopy_size > OVL_METACOPY_MIN_SIZE)
-                       ovl_set_flag(OVL_HAS_DIGEST, inode);
+                       ovl_set_flag(OVL_HAS_DIGEST, ctx->inode);
        }
 
-       ovl_dentry_init_reval(dentry, upperdentry, OVL_I_E(inode));
+       ovl_dentry_init_reval(dentry, ctx->upperdentry, OVL_I_E(ctx->inode));
+
+       return 0;
+}
+
+struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
+                         unsigned int flags)
+{
+       const struct cred *old_cred;
+       struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
+       struct ovl_entry *poe = OVL_E(dentry->d_parent);
+       bool check_redirect = (ovl_redirect_follow(ofs) || ofs->numdatalayer);
+       int err;
+       struct ovl_lookup_ctx ctx = {
+               .dentry = dentry,
+       };
+       struct ovl_lookup_data d = {
+               .sb     = dentry->d_sb,
+               .dentry = dentry,
+               .name   = dentry->d_name,
+               .last   = check_redirect ? false : !ovl_numlower(poe),
+       };
+
+       if (dentry->d_name.len > ofs->namelen)
+               return ERR_PTR(-ENAMETOOLONG);
+
+       old_cred = ovl_override_creds(dentry->d_sb);
+
+       err = ovl_lookup_layers(&ctx, &d);
 
        ovl_revert_creds(old_cred);
-       if (origin_path) {
-               dput(origin_path->dentry);
-               kfree(origin_path);
+       if (ctx.origin_path) {
+               dput(ctx.origin_path->dentry);
+               kfree(ctx.origin_path);
        }
-       dput(index);
-       ovl_stack_free(stack, ctr);
+       dput(ctx.index);
+       ovl_stack_free(ctx.stack, ctx.ctr);
        kfree(d.redirect);
-       return d_splice_alias(inode, dentry);
 
-out_free_oe:
-       ovl_free_entry(oe);
-out_put:
-       dput(index);
-       ovl_stack_free(stack, ctr);
-out_put_upper:
-       if (origin_path) {
-               dput(origin_path->dentry);
-               kfree(origin_path);
+       if (err) {
+               ovl_free_entry(ctx.oe);
+               dput(ctx.upperdentry);
+               kfree(d.upperredirect);
+               return ERR_PTR(err);
        }
-       dput(upperdentry);
-       kfree(d.upperredirect);
-out:
-       kfree(d.redirect);
-       ovl_revert_creds(old_cred);
-       return ERR_PTR(err);
+
+       return d_splice_alias(ctx.inode, dentry);
 }
 
 bool ovl_lower_positive(struct dentry *dentry)