ksmbd: validate num_aces field of smb_acl validation

parse_dcal() validate num_aces to allocate posix_ace_state_array.

if (num_aces > ULONG_MAX / sizeof(struct smb_ace *))

It is an incorrect validation that we can create an array of size ULONG_MAX.
smb_acl has ->size field to calculate actual number of aces in request buffer
size. Use this to check for invalid num_aces.

Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3")
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

Author: namjaejeon

smbacl.c

@@ -387,7 +387,7 @@ void posix_state_to_acl(struct posix_acl_state *state,
 	pace->e_perm = state->other.allow;
 }
 
-int init_acl_state(struct posix_acl_state *state, int cnt)
+int init_acl_state(struct posix_acl_state *state, u16 cnt)
 {
 	int alloc;
 
@@ -426,7 +426,7 @@ static void parse_dacl(struct user_namespace *user_ns,
 		       struct smb_fattr *fattr)
 {
 	int i, ret;
-	int num_aces = 0;
+	u16 num_aces = 0;
 	unsigned int acl_size;
 	char *acl_base;
 	struct smb_ace **ppace;
@@ -447,16 +447,18 @@ static void parse_dacl(struct user_namespace *user_ns,
 
 	ksmbd_debug(SMB, "DACL revision %d size %d num aces %d\n",
 		    le16_to_cpu(pdacl->revision), le16_to_cpu(pdacl->size),
-		    le32_to_cpu(pdacl->num_aces));
+		    le16_to_cpu(pdacl->num_aces));
 
 	acl_base = (char *)pdacl;
 	acl_size = sizeof(struct smb_acl);
 
-	num_aces = le32_to_cpu(pdacl->num_aces);
+	num_aces = le16_to_cpu(pdacl->num_aces);
 	if (num_aces <= 0)
 		return;
 
-	if (num_aces > ULONG_MAX / sizeof(struct smb_ace *))
+	if (num_aces > (pdacl->size - sizeof(struct smb_acl)) /
+			(offsetof(struct smb_ace, sid) +
+			 offsetof(struct smb_sid, sub_auth) + sizeof(__le16)))
 		return;
 
 	ret = init_acl_state(&acl_state, num_aces);
@@ -490,6 +492,7 @@ static void parse_dacl(struct user_namespace *user_ns,
 			offsetof(struct smb_sid, sub_auth);
 
 		if (end_of_acl - acl_base < acl_size ||
+		    ppace[i]->sid.num_subauth == 0 ||
 		    ppace[i]->sid.num_subauth > SID_MAX_SUB_AUTHORITIES ||
 		    (end_of_acl - acl_base <
 		     acl_size + sizeof(__le32) * ppace[i]->sid.num_subauth) ||
@@ -646,7 +649,7 @@ static void set_posix_acl_entries_dacl(struct mnt_idmap *idmap,
 static void set_posix_acl_entries_dacl(struct user_namespace *user_ns,
 #endif
 				       struct smb_ace *pndace,
-				       struct smb_fattr *fattr, u32 *num_aces,
+				       struct smb_fattr *fattr, u16 *num_aces,
 				       u16 *size, u32 nt_aces_num)
 {
 	struct posix_acl_entry *pace;
@@ -787,7 +790,7 @@ static void set_ntacl_dacl(struct user_namespace *user_ns,
 			   struct smb_fattr *fattr)
 {
 	struct smb_ace *ntace, *pndace;
-	int nt_num_aces = le32_to_cpu(nt_dacl->num_aces), num_aces = 0;
+	u16 nt_num_aces = le16_to_cpu(nt_dacl->num_aces), num_aces = 0;
 	unsigned short size = 0;
 	int i;
 
@@ -830,7 +833,7 @@ static void set_mode_dacl(struct user_namespace *user_ns,
 			  struct smb_acl *pndacl, struct smb_fattr *fattr)
 {
 	struct smb_ace *pace, *pndace;
-	u32 num_aces = 0;
+	u16 num_aces = 0;
 	u16 size = 0, ace_size = 0;
 	uid_t uid;
 	const struct smb_sid *sid;
@@ -890,7 +893,7 @@ static void set_mode_dacl(struct user_namespace *user_ns,
 				 fattr->cf_mode, 0007);
 
 out:
-	pndacl->num_aces = cpu_to_le32(num_aces);
+	pndacl->num_aces = cpu_to_le16(num_aces);
 	pndacl->size = cpu_to_le16(le16_to_cpu(pndacl->size) + size);
 }
 
@@ -1137,7 +1140,8 @@ int smb_inherit_dacl(struct ksmbd_conn *conn,
 	struct user_namespace *user_ns = mnt_user_ns(path->mnt);
 #endif
 	int inherited_flags = 0, flags = 0, i, ace_cnt = 0, nt_size = 0, pdacl_size;
-	int rc = 0, num_aces, dacloffset, pntsd_type, pntsd_size, acl_len, aces_size;
+	int rc = 0, dacloffset, pntsd_type, pntsd_size, acl_len, aces_size;
+	u16 num_aces;
 	char *aces_base;
 	bool is_dir = S_ISDIR(d_inode(path->dentry)->i_mode);
 
@@ -1157,7 +1161,7 @@ int smb_inherit_dacl(struct ksmbd_conn *conn,
 
 	parent_pdacl = (struct smb_acl *)((char *)parent_pntsd + dacloffset);
 	acl_len = pntsd_size - dacloffset;
-	num_aces = le32_to_cpu(parent_pdacl->num_aces);
+	num_aces = le16_to_cpu(parent_pdacl->num_aces);
 	pntsd_type = le16_to_cpu(parent_pntsd->type);
 	pdacl_size = le16_to_cpu(parent_pdacl->size);
 
@@ -1317,7 +1321,7 @@ int smb_inherit_dacl(struct ksmbd_conn *conn,
 			pdacl = (struct smb_acl *)((char *)pntsd + le32_to_cpu(pntsd->dacloffset));
 			pdacl->revision = cpu_to_le16(2);
 			pdacl->size = cpu_to_le16(sizeof(struct smb_acl) + nt_size);
-			pdacl->num_aces = cpu_to_le32(ace_cnt);
+			pdacl->num_aces = cpu_to_le16(ace_cnt);
 			pace = (struct smb_ace *)((char *)pdacl + sizeof(struct smb_acl));
 			memcpy(pace, aces_base, nt_size);
 			pntsd_size += sizeof(struct smb_acl) + nt_size;
@@ -1411,7 +1415,7 @@ int smb_check_perm_dacl(struct ksmbd_conn *conn, const struct path *path,
 
 		ace = (struct smb_ace *)((char *)pdacl + sizeof(struct smb_acl));
 		aces_size = acl_size - sizeof(struct smb_acl);
-		for (i = 0; i < le32_to_cpu(pdacl->num_aces); i++) {
+		for (i = 0; i < le16_to_cpu(pdacl->num_aces); i++) {
 			if (offsetof(struct smb_ace, access_req) > aces_size)
 				break;
 			ace_size = le16_to_cpu(ace->size);
@@ -1432,7 +1436,7 @@ int smb_check_perm_dacl(struct ksmbd_conn *conn, const struct path *path,
 
 	ace = (struct smb_ace *)((char *)pdacl + sizeof(struct smb_acl));
 	aces_size = acl_size - sizeof(struct smb_acl);
-	for (i = 0; i < le32_to_cpu(pdacl->num_aces); i++) {
+	for (i = 0; i < le16_to_cpu(pdacl->num_aces); i++) {
 		if (offsetof(struct smb_ace, access_req) > aces_size)
 			break;
 		ace_size = le16_to_cpu(ace->size);

smbacl.h

@@ -140,7 +140,8 @@ struct smb_sid {
 struct smb_acl {
 	__le16 revision; /* revision level */
 	__le16 size;
-	__le32 num_aces;
+	__le16 num_aces;
+	__le16 reserved;
 } __packed;
 
 struct smb_ace {
@@ -206,7 +207,7 @@ int build_sec_desc(struct user_namespace *user_ns, struct smb_ntsd *pntsd,
 #endif
 		   struct smb_ntsd *ppntsd, int ppntsd_size, int addition_info,
 		   __u32 *secdesclen, struct smb_fattr *fattr);
-int init_acl_state(struct posix_acl_state *state, int cnt);
+int init_acl_state(struct posix_acl_state *state, u16 cnt);
 void free_acl_state(struct posix_acl_state *state);
 void posix_state_to_acl(struct posix_acl_state *state,
 			struct posix_acl_entry *pace);