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exfat: move freeing sbi, upcase table and dropping nls into rcu-delayed helper

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That stuff can be accessed by ->d_hash()/->d_compare(); as it is, we have
a hard-to-hit UAF if rcu pathwalk manages to get into ->d_hash() on a filesystem
that is in process of getting shut down.

Besides, having nls and upcase table cleanup moved from ->put_super() towards
the place where sbi is freed makes for simpler failure exits.

Acked-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2023-09-19 15:53:32 -04:00
parent 529f89a9e4
commit a13d1a4de3
3 changed files with 16 additions and 19 deletions
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1
fs/exfat/exfat_fs.h
View File

@ -275,6 +275,7 @@ struct exfat_sb_info {
spinlock_t inode_hash_lock;
struct hlist_head inode_hashtable[EXFAT_HASH_SIZE];
struct rcu_head rcu;
};
#define EXFAT_CACHE_VALID 0

14
fs/exfat/nls.c
View File

@ -655,7 +655,6 @@ static int exfat_load_upcase_table(struct super_block *sb,
unsigned int sect_size = sb->s_blocksize;
unsigned int i, index = 0;
u32 chksum = 0;
int ret;
unsigned char skip = false;
unsigned short *upcase_table;
@ -673,8 +672,7 @@ static int exfat_load_upcase_table(struct super_block *sb,
if (!bh) {
exfat_err(sb, "failed to read sector(0x%llx)",
(unsigned long long)sector);
ret = -EIO;
goto free_table;
return -EIO;
}
sector++;
for (i = 0; i < sect_size && index <= 0xFFFF; i += 2) {
@ -701,15 +699,12 @@ static int exfat_load_upcase_table(struct super_block *sb,
exfat_err(sb, "failed to load upcase table (idx : 0x%08x, chksum : 0x%08x, utbl_chksum : 0x%08x)",
index, chksum, utbl_checksum);
ret = -EINVAL;
free_table:
exfat_free_upcase_table(sbi);
return ret;
return -EINVAL;
}
static int exfat_load_default_upcase_table(struct super_block *sb)
{
int i, ret = -EIO;
int i;
struct exfat_sb_info *sbi = EXFAT_SB(sb);
unsigned char skip = false;
unsigned short uni = 0, *upcase_table;
@ -740,8 +735,7 @@ static int exfat_load_default_upcase_table(struct super_block *sb)
return 0;
/* FATAL error: default upcase table has error */
exfat_free_upcase_table(sbi);
return ret;
return -EIO;
}
int exfat_create_upcase_table(struct super_block *sb)

20
fs/exfat/super.c
View File

@ -39,9 +39,6 @@ static void exfat_put_super(struct super_block *sb)
exfat_free_bitmap(sbi);
brelse(sbi->boot_bh);
mutex_unlock(&sbi->s_lock);
unload_nls(sbi->nls_io);
exfat_free_upcase_table(sbi);
}
static int exfat_sync_fs(struct super_block *sb, int wait)
@ -600,7 +597,7 @@ static int __exfat_fill_super(struct super_block *sb)
ret = exfat_load_bitmap(sb);
if (ret) {
exfat_err(sb, "failed to load alloc-bitmap");
goto free_upcase_table;
goto free_bh;
}
ret = exfat_count_used_clusters(sb, &sbi->used_clusters);
@ -613,8 +610,6 @@ static int __exfat_fill_super(struct super_block *sb)
free_alloc_bitmap:
exfat_free_bitmap(sbi);
free_upcase_table:
exfat_free_upcase_table(sbi);
free_bh:
brelse(sbi->boot_bh);
return ret;
@ -701,12 +696,10 @@ put_inode:
sb->s_root = NULL;
free_table:
exfat_free_upcase_table(sbi);
exfat_free_bitmap(sbi);
brelse(sbi->boot_bh);
check_nls_io:
unload_nls(sbi->nls_io);
return err;
}
@ -771,13 +764,22 @@ static int exfat_init_fs_context(struct fs_context *fc)
return 0;
}
static void delayed_free(struct rcu_head *p)
{
struct exfat_sb_info *sbi = container_of(p, struct exfat_sb_info, rcu);
unload_nls(sbi->nls_io);
exfat_free_upcase_table(sbi);
exfat_free_sbi(sbi);
}
static void exfat_kill_sb(struct super_block *sb)
{
struct exfat_sb_info *sbi = sb->s_fs_info;
kill_block_super(sb);
if (sbi)
exfat_free_sbi(sbi);
call_rcu(&sbi->rcu, delayed_free);
}
static struct file_system_type exfat_fs_type = {