From 39bfcb8138f6dc3375f23b1e62ccfc7c0d83295d Mon Sep 17 00:00:00 2001 From: Jingbo Xu Date: Fri, 21 Oct 2022 10:31:53 +0800 Subject: [PATCH] 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: c6be2bd0a5dd ("erofs: register fscache volume") Fixes: 8b7adf1dff3d ("erofs: introduce fscache-based domain") Signed-off-by: Jingbo Xu Reviewed-by: Jia Zhu Reviewed-by: Chao Yu Link: https://lore.kernel.org/r/20221021023153.1330-1-jefflexu@linux.alibaba.com Signed-off-by: Gao Xiang --- fs/erofs/fscache.c | 14 +++++++------- fs/erofs/internal.h | 6 ++++-- fs/erofs/super.c | 39 ++++++++++++++++++++++----------------- fs/erofs/sysfs.c | 8 ++++---- 4 files changed, 37 insertions(+), 30 deletions(-) diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c index 260fa4737fc0..6eaf4a4ab95c 100644 --- a/fs/erofs/fscache.c +++ b/fs/erofs/fscache.c @@ -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); diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h index 1701df48c446..05dc68627722 100644 --- a/fs/erofs/internal.h +++ b/fs/erofs/internal.h @@ -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) diff --git a/fs/erofs/super.c b/fs/erofs/super.c index 2cf96ce1c32e..1c7dcca702b3 100644 --- a/fs/erofs/super.c +++ b/fs/erofs/super.c @@ -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; } diff --git a/fs/erofs/sysfs.c b/fs/erofs/sysfs.c index 783bb7b21b51..fd476961f742 100644 --- a/fs/erofs/sysfs.c +++ b/fs/erofs/sysfs.c @@ -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; -- 2.11.0