[PATCH v4 4/5] exfat: add dir-entry set checksum validation

Tetsuhiro Kohada
2020-08-26T11:58:40Z

Add checksum validation for dir-entry set when getting it.
exfat_calc_entry_set_chksum_with() also validates entry-type.

Signed-off-by: Tetsuhiro Kohada <kohada.t2@gmail.com>
---
Changes in v2
- Add error log if checksum mismatch
Changes in v3:
- Nothing
Changes in v4:
- Into patch series '[PATCH v4] exfat: integrates dir-entry getting and validation'

fs/exfat/dir.c | 34 +++++++++++++++++++++++-----------
1 file changed, 23 insertions(+), 11 deletions(-)

diff --git a/fs/exfat/dir.c b/fs/exfat/dir.c
index cd37091844fa..d4beea796708 100644
--- a/fs/exfat/dir.c
+++ b/fs/exfat/dir.c
@@ -565,18 +565,26 @@ int exfat_remove_entries(struct inode *inode, struct exfat_chain *p_dir,
return 0;
}

-void exfat_update_dir_chksum_with_entry_set(struct exfat_entry_set_cache *es)
+static int exfat_calc_entry_set_chksum(struct exfat_entry_set_cache *es, u16 *chksum)
{
- int chksum_type = CS_DIR_ENTRY, i;
- u16 chksum = 0;
struct exfat_dentry *ep;
+ int i;

- for (i = 0; i < es->num_entries; i++) {
- ep = exfat_get_validated_dentry(es, i, TYPE_ALL);
- chksum = exfat_calc_chksum16(ep, DENTRY_SIZE, chksum,
- chksum_type);
- chksum_type = CS_DEFAULT;
+ *chksum = exfat_calc_chksum16(es->ep_file, DENTRY_SIZE, 0, CS_DIR_ENTRY);
+ for (i = 0; i < ES_FILE(es).num_ext; i++) {
+ ep = exfat_get_validated_dentry(es, 1 + i, TYPE_SECONDARY);
+ if (!ep)
+ return -EIO;
+ *chksum = exfat_calc_chksum16(ep, DENTRY_SIZE, *chksum, CS_DEFAULT);
}
+ return 0;
+}
+
+void exfat_update_dir_chksum_with_entry_set(struct exfat_entry_set_cache *es)
+{
+ u16 chksum;
+
+ exfat_calc_entry_set_chksum(es, &chksum);
ES_FILE(es).checksum = cpu_to_le16(chksum);
es->modified = true;
}
@@ -776,6 +784,7 @@ struct exfat_entry_set_cache *exfat_get_dentry_set(struct super_block *sb,
struct exfat_sb_info *sbi = EXFAT_SB(sb);
struct exfat_entry_set_cache *es;
struct buffer_head *bh;
+ u16 chksum;

if (p_dir->dir == DIR_DELETED) {
exfat_err(sb, "access to deleted dentry");
@@ -839,9 +848,12 @@ struct exfat_entry_set_cache *exfat_get_dentry_set(struct super_block *sb,
goto free_es;

if (max_entries == ES_ALL_ENTRIES) {
- for (i = 0; i < ES_FILE(es).num_ext; i++)
- if (!exfat_get_validated_dentry(es, ES_INDEX_STREAM + i, TYPE_SECONDARY))
- goto free_es;
+ if (exfat_calc_entry_set_chksum(es, &chksum) ||
+ chksum != le16_to_cpu(ES_FILE(es).checksum)) {
+ exfat_err(sb, "invalid entry-set checksum (entry : 0x%08x, set-checksum : 0x%04x, checksum : 0x%04x)",
+ entry, le16_to_cpu(ES_FILE(es).checksum), chksum);
+ goto free_es;
+ }
for (i = 0; i * EXFAT_FILE_NAME_LEN < ES_STREAM(es).name_len; i++)
if (!exfat_get_validated_dentry(es, ES_INDEX_NAME + i, TYPE_NAME))
goto free_es;
--
2.25.1