From c40235720ee0a742f4d8aca2333e1ccad726269a Mon Sep 17 00:00:00 2001
From: Karel Zak <kzak@redhat.com>
Date: Wed, 22 May 2024 10:52:04 +0200
Subject: [PATCH] libmount: add functions to use error buffer

* Add mnt_context_set_errmsg() and mnt_context_append_errmsg() functions.
* Replace custom code with mnt_context_syscall_save_status() function.
* Optionally use syscall name when generating error message.

Signed-off-by: Karel Zak <kzak@redhat.com>
---
 libmount/src/context.c           | 31 +++++++++++++++++++++++++++++--
 libmount/src/context_mount.c     | 11 +++++++----
 libmount/src/hook_mount.c        |  8 ++------
 libmount/src/hook_mount_legacy.c | 11 +++--------
 libmount/src/mountP.h            |  5 ++++-
 5 files changed, 45 insertions(+), 21 deletions(-)

diff --git a/libmount/src/context.c b/libmount/src/context.c
index ef5da32a0d..7cf4ef79ed 100644
--- a/libmount/src/context.c
+++ b/libmount/src/context.c
@@ -2635,8 +2635,35 @@ void mnt_context_syscall_reset_status(struct libmnt_context *cxt)
 	cxt->syscall_status = 0;
 	cxt->syscall_name = NULL;
 
-	free(cxt->syscall_errmsg);
-	cxt->syscall_errmsg = NULL;
+	free(cxt->errmsg);
+	cxt->errmsg = NULL;
+}
+
+int mnt_context_set_errmsg(struct libmnt_context *cxt, const char *msg)
+{
+	char *p = NULL;
+
+	if (msg) {
+		p = strdup(msg);
+		if (!p)
+			return -ENOMEM;
+	}
+
+	free(cxt->errmsg);
+	cxt->errmsg = p;
+
+	return 0;
+}
+
+int mnt_context_append_errmsg(struct libmnt_context *cxt, const char *msg)
+{
+	if (cxt->errmsg) {
+		int rc = strappend(&cxt->errmsg, "; ");
+		if (rc)
+			return rc;
+	}
+
+	return strappend(&cxt->errmsg, msg);
 }
 
 /**
diff --git a/libmount/src/context_mount.c b/libmount/src/context_mount.c
index f9d610f778..783244a61c 100644
--- a/libmount/src/context_mount.c
+++ b/libmount/src/context_mount.c
@@ -1572,10 +1572,13 @@ int mnt_context_get_mount_excode(
 	 */
 	syserr = mnt_context_get_syscall_errno(cxt);
 
-	if (buf && cxt->syscall_errmsg) {
-		snprintf(buf, bufsz, _("%s system call failed: %s"),
-					cxt->syscall_name ? : "mount",
-					cxt->syscall_errmsg);
+	if (buf && cxt->errmsg) {
+		if (cxt->syscall_name)
+			snprintf(buf, bufsz, _("%s system call failed: %s"),
+					cxt->syscall_name, cxt->errmsg);
+		else
+			xstrncpy(buf, cxt->errmsg, bufsz);
+
 		return MNT_EX_FAIL;
 	}
 
diff --git a/libmount/src/hook_mount.c b/libmount/src/hook_mount.c
index c85c92b983..6b7caff853 100644
--- a/libmount/src/hook_mount.c
+++ b/libmount/src/hook_mount.c
@@ -70,8 +70,7 @@ static void save_fd_messages(struct libmnt_context *cxt, int fd)
 	uint8_t buf[BUFSIZ];
 	int rc;
 
-	free(cxt->syscall_errmsg);
-	cxt->syscall_errmsg = NULL;
+	mnt_context_set_errmsg(cxt, NULL);
 
 	while ((rc = read(fd, buf, sizeof(buf))) != -1) {
 		if (rc > 0 && buf[rc - 1] == '\n')
@@ -80,10 +79,7 @@ static void save_fd_messages(struct libmnt_context *cxt, int fd)
 
 		if (rc < 3 || strncmp((char *) buf, "e ", 2) != 0)
 			continue;
-		if (cxt->syscall_errmsg)
-			strappend(&cxt->syscall_errmsg, "; ");
-
-		strappend(&cxt->syscall_errmsg, ((char *) buf) + 2);
+		mnt_context_append_errmsg(cxt, ((char *) buf) + 2);
 	}
 }
 
diff --git a/libmount/src/hook_mount_legacy.c b/libmount/src/hook_mount_legacy.c
index 7e62864673..df3a691e0d 100644
--- a/libmount/src/hook_mount_legacy.c
+++ b/libmount/src/hook_mount_legacy.c
@@ -76,10 +76,8 @@ static int hook_propagation(struct libmnt_context *cxt,
 
 	if (rc) {
 		/* Update global syscall status if only this function called */
-		if (mnt_context_propagation_only(cxt)) {
-			cxt->syscall_status = -errno;
-			cxt->syscall_name = "mount";
-		}
+		if (mnt_context_propagation_only(cxt))
+			mnt_context_syscall_save_status(cxt, "mount", rc == 0);
 
 		DBG(HOOK, ul_debugobj(hs, "  mount(2) failed [errno=%d %m]", errno));
 		rc = -MNT_ERR_APPLYFLAGS;
@@ -240,10 +238,7 @@ static int hook_mount(struct libmnt_context *cxt,
 			  options : "<none>"));
 
 	if (mount(src, target, type, flags, options)) {
-		cxt->syscall_status = -errno;
-		cxt->syscall_name = "mount";
-		DBG(HOOK, ul_debugobj(hs, "  mount(2) failed [errno=%d %m]",
-					-cxt->syscall_status));
+		mnt_context_syscall_save_status(cxt, "mount", 0);
 		rc = -cxt->syscall_status;
 		return rc;
 	}
diff --git a/libmount/src/mountP.h b/libmount/src/mountP.h
index 63a9675bbd..db58e9f749 100644
--- a/libmount/src/mountP.h
+++ b/libmount/src/mountP.h
@@ -432,7 +432,7 @@ struct libmnt_context
 
 	int	syscall_status;	/* 1: not called yet, 0: success, <0: -errno */
 	const char *syscall_name;	/* failed syscall name */
-	char	*syscall_errmsg;	/* message from kernel */
+	char	*errmsg;	/* library or kernel message */
 
 	struct libmnt_ns	ns_orig;	/* original namespace */
 	struct libmnt_ns	ns_tgt;		/* target namespace */
@@ -626,6 +626,9 @@ extern int mnt_context_update_tabs(struct libmnt_context *cxt);
 extern int mnt_context_umount_setopt(struct libmnt_context *cxt, int c, char *arg);
 extern int mnt_context_mount_setopt(struct libmnt_context *cxt, int c, char *arg);
 
+extern int mnt_context_set_errmsg(struct libmnt_context *cxt, const char *msg);
+extern int mnt_context_append_errmsg(struct libmnt_context *cxt, const char *msg);
+
 extern int mnt_context_propagation_only(struct libmnt_context *cxt)
 			__attribute__((nonnull));
 
-- 
2.47.2