[PATCH] cifs: set the cred_uid/linux_uid/linux_gid when duplicating contexts

[Ronnie Sahlberg <lsahlber@xxxxxxxxxx>]

Use the nice helpers to initialize and the uid/gid/cred_uid when passed as mount
arguments.
Also, when we duplicate a context, for example in multiuser,cruid=xxx we need to
re-set these uid/gids to the current user or else we may get a crash.

Fixes: 24e0a1eff9e2 ("cifs: switch to new mount api")
Cc: stable@xxxxxxxxxxxxxxx # 5.11
Signed-off-by: Ronnie Sahlberg <lsahlber@xxxxxxxxxx>
---
 fs/cifs/fs_context.c | 27 ++++++++++++++++++++++-----
 fs/cifs/fs_context.h |  1 +
 2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/fs/cifs/fs_context.c b/fs/cifs/fs_context.c
index 92d4ab029c91..39bebe298387 100644
--- a/fs/cifs/fs_context.c
+++ b/fs/cifs/fs_context.c
@@ -322,7 +322,9 @@ smb3_fs_context_dup(struct smb3_fs_context *new_ctx, struct smb3_fs_context *ctx
 	new_ctx->UNC = NULL;
 	new_ctx->source = NULL;
 	new_ctx->iocharset = NULL;
-
+	new_ctx->linux_uid = current_fsuid();
+	new_ctx->cred_uid = current_fsuid();
+	new_ctx->linux_gid = current_fsgid();
 	/*
 	 * Make sure to stay in sync with smb3_cleanup_fs_context_contents()
 	 */
@@ -792,6 +794,8 @@ static int smb3_fs_context_parse_param(struct fs_context *fc,
 	int i, opt;
 	bool is_smb3 = !strcmp(fc->fs_type->name, "smb3");
 	bool skip_parsing = false;
+	kuid_t uid;
+	kgid_t gid;
 
 	cifs_dbg(FYI, "CIFS: parsing cifs mount option '%s'\n", param->key);
 
@@ -904,18 +908,31 @@ static int smb3_fs_context_parse_param(struct fs_context *fc,
 		}
 		break;
 	case Opt_uid:
-		ctx->linux_uid.val = result.uint_32;
+		uid = make_kuid(current_user_ns(), result.uint_32);
+		if (!uid_valid(uid))
+			goto cifs_parse_mount_err;
+		ctx->linux_uid = uid;
 		ctx->uid_specified = true;
 		break;
 	case Opt_cruid:
-		ctx->cred_uid.val = result.uint_32;
+		uid = make_kuid(current_user_ns(), result.uint_32);
+		if (!uid_valid(uid))
+			goto cifs_parse_mount_err;
+		ctx->cred_uid = uid;
+		ctx->cruid_specified = true;
 		break;
 	case Opt_backupgid:
-		ctx->backupgid.val = result.uint_32;
+		gid = make_kgid(current_user_ns(), result.uint_32);
+		if (!gid_valid(gid))
+			goto cifs_parse_mount_err;
+		ctx->backupgid = gid;
 		ctx->backupgid_specified = true;
 		break;
 	case Opt_gid:
-		ctx->linux_gid.val = result.uint_32;
+		gid = make_kgid(current_user_ns(), result.uint_32);
+		if (!gid_valid(gid))
+			goto cifs_parse_mount_err;
+		ctx->linux_gid = gid;
 		ctx->gid_specified = true;
 		break;
 	case Opt_port:
diff --git a/fs/cifs/fs_context.h b/fs/cifs/fs_context.h
index 2a71c8e411ac..b6243972edf3 100644
--- a/fs/cifs/fs_context.h
+++ b/fs/cifs/fs_context.h
@@ -155,6 +155,7 @@ enum cifs_param {
 
 struct smb3_fs_context {
 	bool uid_specified;
+	bool cruid_specified;
 	bool gid_specified;
 	bool sloppy;
 	bool got_ip;
-- 
2.30.2