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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: c6be2bd0a5 ("erofs: register fscache volume")
Fixes: 8b7adf1dff ("erofs: introduce fscache-based domain")
Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Jia Zhu <zhujia.zj@bytedance.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20221021023153.1330-1-jefflexu@linux.alibaba.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
This commit is contained in:
Jingbo Xu 2022-10-21 10:31:53 +08:00 committed by Gao Xiang
parent e6d9f9ba11
commit 39bfcb8138
4 changed files with 37 additions and 30 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
fs/erofs/fscache.c
View File

@ -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);

6
fs/erofs/internal.h
View File

@ -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)

39
fs/erofs/super.c
View File

@ -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;
}

8
fs/erofs/sysfs.c
View File

@ -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;