ksmbd: bound DACL dedup walk to copied ACEs

set_ntacl_dacl() can stop copying ACEs before consuming the full input
DACL when size accounting overflows.

When that happens, num_aces reflects only the ACEs that were actually
copied into the output DACL, but set_posix_acl_entries_dacl() still
receives nt_num_aces and uses it to walk the existing ACE array during
dedup.

That makes the dedup walk scan past the copied ACE array and inspect
buffer tail that does not contain valid ACEs.

Split the two meanings currently carried by the NT ACE count. Pass the
number of copied NT ACEs to bound the dedup walk, and preserve the
original "input DACL had NT ACEs" state separately for the
Everyone/default ACL fallback.

This keeps the dedup walk aligned with the ACEs that are actually
present in the rebuilt DACL.

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 10 insertions, 6 deletions

diff --git a/fs/smb/server/smbacl.c b/fs/smb/server/smbacl.c
index 67b39b4d218c..d28289188e44 100644
--- a/fs/smb/server/smbacl.c
+++ b/fs/smb/server/smbacl.c
@@ -608,7 +608,8 @@ static void parse_dacl(struct mnt_idmap *idmap,
 static void set_posix_acl_entries_dacl(struct mnt_idmap *idmap,
 				       struct smb_ace *pndace,
 				       struct smb_fattr *fattr, u16 *num_aces,
-				       u16 *size, u32 nt_aces_num)
+				       u16 *size, u16 existing_nt_aces,
+				       bool had_nt_aces)
 {
 	struct posix_acl_entry *pace;
 	struct smb_sid *sid;
@@ -640,14 +641,14 @@ static void set_posix_acl_entries_dacl(struct mnt_idmap *idmap,
 
 			gid = posix_acl_gid_translate(idmap, pace);
 			id_to_sid(gid, SIDUNIX_GROUP, sid);
-		} else if (pace->e_tag == ACL_OTHER && !nt_aces_num) {
+		} else if (pace->e_tag == ACL_OTHER && !had_nt_aces) {
 			smb_copy_sid(sid, &sid_everyone);
 		} else {
 			kfree(sid);
 			continue;
 		}
 		ntace = pndace;
-		for (j = 0; j < nt_aces_num; j++) {
+		for (j = 0; j < existing_nt_aces; j++) {
 			if (ntace->sid.sub_auth[ntace->sid.num_subauth - 1] ==
 					sid->sub_auth[sid->num_subauth - 1])
 				goto pass_same_sid;
@@ -689,7 +690,7 @@ pass_same_sid:
 		kfree(sid);
 	}
 
-	if (nt_aces_num)
+	if (had_nt_aces)
 		return;
 
 posix_default_acl:
@@ -742,6 +743,7 @@ static void set_ntacl_dacl(struct mnt_idmap *idmap,
 {
 	struct smb_ace *ntace, *pndace;
 	u16 nt_num_aces = le16_to_cpu(nt_dacl->num_aces), num_aces = 0;
+	u16 copied_nt_aces;
 	unsigned short size = 0;
 	int i;
 
@@ -773,8 +775,10 @@ next_ace:
 		}
 	}
 
+	copied_nt_aces = num_aces;
 	set_posix_acl_entries_dacl(idmap, pndace, fattr,
-				   &num_aces, &size, nt_num_aces);
+				   &num_aces, &size, copied_nt_aces,
+				   nt_num_aces != 0);
 	pndacl->num_aces = cpu_to_le16(num_aces);
 	pndacl->size = cpu_to_le16(le16_to_cpu(pndacl->size) + size);
 }
@@ -792,7 +796,7 @@ static void set_mode_dacl(struct mnt_idmap *idmap,
 
 	if (fattr->cf_acls) {
 		set_posix_acl_entries_dacl(idmap, pndace, fattr,
-					   &num_aces, &size, num_aces);
+					   &num_aces, &size, num_aces, false);
 		goto out;
 	}