Commit 39bfcb81 authored by Jingbo Xu's avatar Jingbo Xu Committed by Gao Xiang
Browse files

erofs: fix use-after-free of fsid and domain_id string 



When erofs instance is remounted with fsid or domain_id mount option
specified, the original fsid and domain_id string pointer in sbi->opt
is directly overridden with the fsid and domain_id string in the new
fs_context, without freeing the original fsid and domain_id string.
What's worse, when the new fsid and domain_id string is transferred to
sbi, they are not reset to NULL in fs_context, and thus they are freed
when remount finishes, while sbi is still referring to these strings.

Reconfiguration for fsid and domain_id seems unusual. Thus clarify this
restriction explicitly and dump a warning when users are attempting to
do this.

Besides, to fix the use-after-free issue, move fsid and domain_id from
erofs_mount_opts to outside.

Fixes: c6be2bd0 ("erofs: register fscache volume")
Fixes: 8b7adf1d ("erofs: introduce fscache-based domain")
Signed-off-by: default avatarJingbo Xu <jefflexu@linux.alibaba.com>
Reviewed-by: default avatarJia Zhu <zhujia.zj@bytedance.com>
Reviewed-by: default avatarChao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20221021023153.1330-1-jefflexu@linux.alibaba.com


Signed-off-by: default avatarGao Xiang <hsiangkao@linux.alibaba.com>
parent e6d9f9ba

fs/erofs/fscache.c

+7 −7
Original line number Diff line number Diff line
@@ -406,13 +406,13 @@ static void erofs_fscache_domain_put(struct erofs_domain *domain) 
static int erofs_fscache_register_volume(struct super_block *sb)

{

	struct erofs_sb_info *sbi = EROFS_SB(sb);

	char *domain_id = sbi->opt.domain_id;

	char *domain_id = sbi->domain_id;

	struct fscache_volume *volume;

	char *name;

	int ret = 0;



	name = kasprintf(GFP_KERNEL, "erofs,%s",

			 domain_id ? domain_id : sbi->opt.fsid);

			 domain_id ? domain_id : sbi->fsid);

	if (!name)

		return -ENOMEM;
@@ -438,7 +438,7 @@ static int erofs_fscache_init_domain(struct super_block *sb) 
	if (!domain)

		return -ENOMEM;



	domain->domain_id = kstrdup(sbi->opt.domain_id, GFP_KERNEL);

	domain->domain_id = kstrdup(sbi->domain_id, GFP_KERNEL);

	if (!domain->domain_id) {

		kfree(domain);

		return -ENOMEM;
@@ -475,7 +475,7 @@ static int erofs_fscache_register_domain(struct super_block *sb) 


	mutex_lock(&erofs_domain_list_lock);

	list_for_each_entry(domain, &erofs_domain_list, list) {

		if (!strcmp(domain->domain_id, sbi->opt.domain_id)) {

		if (!strcmp(domain->domain_id, sbi->domain_id)) {

			sbi->domain = domain;

			sbi->volume = domain->volume;

			refcount_inc(&domain->ref);
@@ -612,7 +612,7 @@ struct erofs_fscache *erofs_domain_register_cookie(struct super_block *sb, 
struct erofs_fscache *erofs_fscache_register_cookie(struct super_block *sb,

						    char *name, bool need_inode)

{

	if (EROFS_SB(sb)->opt.domain_id)

	if (EROFS_SB(sb)->domain_id)

		return erofs_domain_register_cookie(sb, name, need_inode);

	return erofs_fscache_acquire_cookie(sb, name, need_inode);

}
@@ -644,7 +644,7 @@ int erofs_fscache_register_fs(struct super_block *sb) 
	struct erofs_sb_info *sbi = EROFS_SB(sb);

	struct erofs_fscache *fscache;



	if (sbi->opt.domain_id)

	if (sbi->domain_id)

		ret = erofs_fscache_register_domain(sb);

	else

		ret = erofs_fscache_register_volume(sb);
@@ -652,7 +652,7 @@ int erofs_fscache_register_fs(struct super_block *sb) 
		return ret;



	/* acquired domain/volume will be relinquished in kill_sb() on error */

	fscache = erofs_fscache_register_cookie(sb, sbi->opt.fsid, true);

	fscache = erofs_fscache_register_cookie(sb, sbi->fsid, true);

	if (IS_ERR(fscache))

		return PTR_ERR(fscache);

fs/erofs/internal.h

+4 −2
Original line number Diff line number Diff line
@@ -75,8 +75,6 @@ struct erofs_mount_opts { 
	unsigned int max_sync_decompress_pages;

#endif

	unsigned int mount_opt;

	char *fsid;

	char *domain_id;

};



struct erofs_dev_context {
@@ -89,6 +87,8 @@ struct erofs_dev_context { 
struct erofs_fs_context {

	struct erofs_mount_opts opt;

	struct erofs_dev_context *devs;

	char *fsid;

	char *domain_id;

};



/* all filesystem-wide lz4 configurations */
@@ -170,6 +170,8 @@ struct erofs_sb_info { 
	struct fscache_volume *volume;

	struct erofs_fscache *s_fscache;

	struct erofs_domain *domain;

	char *fsid;

	char *domain_id;

};



#define EROFS_SB(sb) ((struct erofs_sb_info *)(sb)->s_fs_info)

fs/erofs/super.c

+22 −17
Original line number Diff line number Diff line
@@ -579,9 +579,9 @@ static int erofs_fc_parse_param(struct fs_context *fc, 
		break;

	case Opt_fsid:

#ifdef CONFIG_EROFS_FS_ONDEMAND

		kfree(ctx->opt.fsid);

		ctx->opt.fsid = kstrdup(param->string, GFP_KERNEL);

		if (!ctx->opt.fsid)

		kfree(ctx->fsid);

		ctx->fsid = kstrdup(param->string, GFP_KERNEL);

		if (!ctx->fsid)

			return -ENOMEM;

#else

		errorfc(fc, "fsid option not supported");
@@ -589,9 +589,9 @@ static int erofs_fc_parse_param(struct fs_context *fc, 
		break;

	case Opt_domain_id:

#ifdef CONFIG_EROFS_FS_ONDEMAND

		kfree(ctx->opt.domain_id);

		ctx->opt.domain_id = kstrdup(param->string, GFP_KERNEL);

		if (!ctx->opt.domain_id)

		kfree(ctx->domain_id);

		ctx->domain_id = kstrdup(param->string, GFP_KERNEL);

		if (!ctx->domain_id)

			return -ENOMEM;

#else

		errorfc(fc, "domain_id option not supported");
@@ -728,10 +728,12 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc) 


	sb->s_fs_info = sbi;

	sbi->opt = ctx->opt;

	ctx->opt.fsid = NULL;

	ctx->opt.domain_id = NULL;

	sbi->devs = ctx->devs;

	ctx->devs = NULL;

	sbi->fsid = ctx->fsid;

	ctx->fsid = NULL;

	sbi->domain_id = ctx->domain_id;

	ctx->domain_id = NULL;



	if (erofs_is_fscache_mode(sb)) {

		sb->s_blocksize = EROFS_BLKSIZ;
@@ -820,7 +822,7 @@ static int erofs_fc_get_tree(struct fs_context *fc) 
{

	struct erofs_fs_context *ctx = fc->fs_private;



	if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && ctx->opt.fsid)

	if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && ctx->fsid)

		return get_tree_nodev(fc, erofs_fc_fill_super);



	return get_tree_bdev(fc, erofs_fc_fill_super);
@@ -834,6 +836,9 @@ static int erofs_fc_reconfigure(struct fs_context *fc) 


	DBG_BUGON(!sb_rdonly(sb));



	if (ctx->fsid || ctx->domain_id)

		erofs_info(sb, "ignoring reconfiguration for fsid|domain_id.");



	if (test_opt(&ctx->opt, POSIX_ACL))

		fc->sb_flags |= SB_POSIXACL;

	else
@@ -873,8 +878,8 @@ static void erofs_fc_free(struct fs_context *fc) 
	struct erofs_fs_context *ctx = fc->fs_private;



	erofs_free_dev_context(ctx->devs);

	kfree(ctx->opt.fsid);

	kfree(ctx->opt.domain_id);

	kfree(ctx->fsid);

	kfree(ctx->domain_id);

	kfree(ctx);

}
@@ -944,8 +949,8 @@ static void erofs_kill_sb(struct super_block *sb) 
	erofs_free_dev_context(sbi->devs);

	fs_put_dax(sbi->dax_dev, NULL);

	erofs_fscache_unregister_fs(sb);

	kfree(sbi->opt.fsid);

	kfree(sbi->opt.domain_id);

	kfree(sbi->fsid);

	kfree(sbi->domain_id);

	kfree(sbi);

	sb->s_fs_info = NULL;

}
@@ -1098,10 +1103,10 @@ static int erofs_show_options(struct seq_file *seq, struct dentry *root) 
	if (test_opt(opt, DAX_NEVER))

		seq_puts(seq, ",dax=never");

#ifdef CONFIG_EROFS_FS_ONDEMAND

	if (opt->fsid)

		seq_printf(seq, ",fsid=%s", opt->fsid);

	if (opt->domain_id)

		seq_printf(seq, ",domain_id=%s", opt->domain_id);

	if (sbi->fsid)

		seq_printf(seq, ",fsid=%s", sbi->fsid);

	if (sbi->domain_id)

		seq_printf(seq, ",domain_id=%s", sbi->domain_id);

#endif

	return 0;

}

fs/erofs/sysfs.c

+4 −4
Original line number Diff line number Diff line
@@ -210,14 +210,14 @@ int erofs_register_sysfs(struct super_block *sb) 
	int err;



	if (erofs_is_fscache_mode(sb)) {

		if (sbi->opt.domain_id) {

			str = kasprintf(GFP_KERNEL, "%s,%s", sbi->opt.domain_id,

					sbi->opt.fsid);

		if (sbi->domain_id) {

			str = kasprintf(GFP_KERNEL, "%s,%s", sbi->domain_id,

					sbi->fsid);

			if (!str)

				return -ENOMEM;

			name = str;

		} else {

			name = sbi->opt.fsid;

			name = sbi->fsid;

		}

	} else {

		name = sb->s_id;