From: Karel Zak <kzak@redhat.com>
Date: Tue, 18 Apr 2023 13:54:25 +0000 (+0200)
Subject: libmount: cleanup all stat() use
X-Git-Tag: v2.39-rc3~14
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=f2663ba7d26283195b158b70038a04098080588c;p=thirdparty%2Futil-linux.git

libmount: cleanup all stat() use

* don't use STATX_MODE as we need only file type
* use fstatat() or stat() as fallback on EOPNOTSUPP
* use st_rdev from statx() too

* rename to mnt_stat_mountpoint() to more generic mnt_safe_stat()

* use mnt_is_path() on more places
* cleanup mnt_context_*_excode() to not use stat()
* use on others places mnt_safe_stat()

Note that on some places stat() remaining, but it's not related to the
mountpoints, it's about /run/mount/utab permissions, file locking and
/dev/* permissions for non-root mounts.

Signed-off-by: Karel Zak <kzak@redhat.com>
---

diff --git a/libmount/src/context.c b/libmount/src/context.c
index 2df4716a71..4c5e65659f 100644
--- a/libmount/src/context.c
+++ b/libmount/src/context.c
@@ -1407,7 +1407,7 @@ int mnt_context_get_mountinfo_for_target(struct libmnt_context *cxt,
 	if (mnt_context_is_nocanonicalize(cxt))
 		mnt_context_set_tabfilter(cxt, mountinfo_filter, (void *) tgt);
 
-	else if (mnt_stat_mountpoint(tgt, &st) == 0 && S_ISDIR(st.st_mode)) {
+	else if (mnt_safe_stat(tgt, &st) == 0 && S_ISDIR(st.st_mode)) {
 		cache = mnt_context_get_cache(cxt);
 		cn_tgt = mnt_resolve_path(tgt, cache);
 		if (cn_tgt)
@@ -2025,34 +2025,32 @@ int mnt_context_prepare_helper(struct libmnt_context *cxt, const char *name,
 	if (!ns_old)
 		return -MNT_ERR_NAMESPACE;
 
-	/* Ignore errors when search in $PATH and do not modify
-	 * @rc due to stat() etc.
+	/* Ignore errors when search in $PATH and do not modify @rc
 	 */
 	path = strtok_r(search_path, ":", &p);
 	while (path) {
 		char helper[PATH_MAX];
-		struct stat st;
-		int xrc;
+		int len, found = 0;
 
-		xrc = snprintf(helper, sizeof(helper), "%s/%s.%s",
+		len = snprintf(helper, sizeof(helper), "%s/%s.%s",
 						path, name, type);
 		path = strtok_r(NULL, ":", &p);
 
-		if (xrc < 0 || (size_t) xrc >= sizeof(helper))
+		if (len < 0 || (size_t) len >= sizeof(helper))
 			continue;
 
-		xrc = stat(helper, &st);
-		if (xrc == -1 && errno == ENOENT && strchr(type, '.')) {
+		found = mnt_is_path(helper);
+		if (!found && strchr(type, '.')) {
 			/* If type ends with ".subtype" try without it */
 			char *hs = strrchr(helper, '.');
 			if (hs)
 				*hs = '\0';
-			xrc = stat(helper, &st);
+			found = mnt_is_path(helper);
 		}
 
 		DBG(CXT, ul_debugobj(cxt, "%-25s ... %s", helper,
-					xrc ? "not found" : "found"));
-		if (xrc)
+					found ? "found" : "not found"));
+		if (!found)
 			continue;
 
 		/* success */
diff --git a/libmount/src/context_mount.c b/libmount/src/context_mount.c
index 7bda266825..b8499471af 100644
--- a/libmount/src/context_mount.c
+++ b/libmount/src/context_mount.c
@@ -1558,7 +1558,7 @@ int mnt_context_get_mount_excode(
 		if (!buf)
 			break;
 		if (geteuid() == 0) {
-			if (mnt_stat_mountpoint(tgt, &st) || !S_ISDIR(st.st_mode))
+			if (mnt_safe_stat(tgt, &st) || !S_ISDIR(st.st_mode))
 				snprintf(buf, bufsz, _("mount point is not a directory"));
 			else
 				snprintf(buf, bufsz, _("permission denied"));
@@ -1584,13 +1584,13 @@ int mnt_context_get_mount_excode(
 			snprintf(buf, bufsz, _("%s already mounted or mount point busy"), src);
 		break;
 	case ENOENT:
-		if (tgt && mnt_lstat_mountpoint(tgt, &st)) {
+		if (tgt && mnt_safe_lstat(tgt, &st)) {
 			if (buf)
 				snprintf(buf, bufsz, _("mount point does not exist"));
-		} else if (tgt && mnt_stat_mountpoint(tgt, &st)) {
+		} else if (tgt && mnt_safe_stat(tgt, &st)) {
 			if (buf)
 				snprintf(buf, bufsz, _("mount point is a symbolic link to nowhere"));
-		} else if (src && stat(src, &st)) {
+		} else if (src && !mnt_is_path(src)) {
 			if (uflags & MNT_MS_NOFAIL)
 				return MNT_EX_SUCCESS;
 			if (buf)
@@ -1602,10 +1602,10 @@ int mnt_context_get_mount_excode(
 		break;
 
 	case ENOTDIR:
-		if (mnt_stat_mountpoint(tgt, &st) || ! S_ISDIR(st.st_mode)) {
+		if (mnt_safe_stat(tgt, &st) || ! S_ISDIR(st.st_mode)) {
 			if (buf)
 				snprintf(buf, bufsz, _("mount point is not a directory"));
-		} else if (src && stat(src, &st) && errno == ENOTDIR) {
+		} else if (src && !mnt_is_path(src)) {
 			if (uflags & MNT_MS_NOFAIL)
 				return MNT_EX_SUCCESS;
 			if (buf)
@@ -1664,7 +1664,7 @@ int mnt_context_get_mount_excode(
 			return MNT_EX_SUCCESS;
 		if (!buf)
 			break;
-		if (src && stat(src, &st))
+		if (src && mnt_safe_stat(src, &st))
 			snprintf(buf, bufsz, _("%s is not a block device, and stat(2) fails?"), src);
 		else if (src && S_ISBLK(st.st_mode))
 			snprintf(buf, bufsz,
@@ -1710,7 +1710,7 @@ int mnt_context_get_mount_excode(
 
 	case EBADMSG:
 		/* Bad CRC for classic filesystems (e.g. extN or XFS) */
-		if (buf && src && stat(src, &st) == 0
+		if (buf && src && mnt_safe_stat(src, &st) == 0
 		    && (S_ISBLK(st.st_mode) || S_ISREG(st.st_mode))) {
 			snprintf(buf, bufsz, _("cannot mount; probably corrupted filesystem on %s"), src);
 			break;
diff --git a/libmount/src/context_umount.c b/libmount/src/context_umount.c
index efb6675b3a..26394d51ef 100644
--- a/libmount/src/context_umount.c
+++ b/libmount/src/context_umount.c
@@ -134,7 +134,7 @@ try_loopdev:
 		 */
 		struct stat st;
 
-		if (mnt_stat_mountpoint(tgt, &st) == 0 && S_ISREG(st.st_mode)) {
+		if (mnt_safe_stat(tgt, &st) == 0 && S_ISREG(st.st_mode)) {
 			int count;
 			struct libmnt_cache *cache = mnt_context_get_cache(cxt);
 			const char *bf = cache ? mnt_resolve_path(tgt, cache) : tgt;
@@ -275,7 +275,7 @@ static int lookup_umount_fs_by_statfs(struct libmnt_context *cxt, const char *tg
 	    || mnt_context_is_lazy(cxt)
 	    || mnt_context_is_nocanonicalize(cxt)
 	    || mnt_context_is_loopdel(cxt)
-	    || mnt_stat_mountpoint(tgt, &st) != 0 || !S_ISDIR(st.st_mode)
+	    || mnt_safe_stat(tgt, &st) != 0 || !S_ISDIR(st.st_mode)
 	    || has_utab_entry(cxt, tgt))
 		return 1; /* not found */
 
diff --git a/libmount/src/mountP.h b/libmount/src/mountP.h
index 4af212388c..bceb04a92b 100644
--- a/libmount/src/mountP.h
+++ b/libmount/src/mountP.h
@@ -128,8 +128,8 @@ extern void mnt_free_filesystems(char **filesystems);
 
 extern char *mnt_get_kernel_cmdline_option(const char *name);
 
-extern int mnt_stat_mountpoint(const char *target, struct stat *st);
-extern int mnt_lstat_mountpoint(const char *target, struct stat *st);
+extern int mnt_safe_stat(const char *target, struct stat *st);
+extern int mnt_safe_lstat(const char *target, struct stat *st);
 extern int mnt_is_path(const char *target);
 
 extern int mnt_tmptgt_unshare(int *old_ns_fd);
diff --git a/libmount/src/tab.c b/libmount/src/tab.c
index d8b239b305..60bef8b2d1 100644
--- a/libmount/src/tab.c
+++ b/libmount/src/tab.c
@@ -1775,7 +1775,7 @@ int __mnt_table_is_fs_mounted(struct libmnt_table *tb, struct libmnt_fs *fstab_f
 		struct stat st;
 
 		devno = mnt_fs_get_devno(fstab_fs);
-		if (!devno && stat(src, &st) == 0 && S_ISBLK(st.st_mode))
+		if (!devno && mnt_safe_stat(src, &st) == 0 && S_ISBLK(st.st_mode))
 			devno = st.st_rdev;
 	}
 
diff --git a/libmount/src/tab_parse.c b/libmount/src/tab_parse.c
index 526a0078bb..b8ec244f79 100644
--- a/libmount/src/tab_parse.c
+++ b/libmount/src/tab_parse.c
@@ -974,11 +974,10 @@ int mnt_table_parse_dir(struct libmnt_table *tb, const char *dirname)
 struct libmnt_table *__mnt_new_table_from_file(const char *filename, int fmt, int empty_for_enoent)
 {
 	struct libmnt_table *tb;
-	struct stat st;
 
 	if (!filename)
 		return NULL;
-	if (stat(filename, &st))
+	if (!mnt_is_path(filename))
 		return empty_for_enoent ? mnt_new_table() : NULL;
 
 	tb = mnt_new_table();
@@ -1149,7 +1148,7 @@ int mnt_table_parse_fstab(struct libmnt_table *tb, const char *filename)
 		filename = mnt_get_fstab_path();
 	if (!filename)
 		return -EINVAL;
-	if (stat(filename, &st) != 0)
+	if (mnt_safe_stat(filename, &st) != 0)
 		return -errno;
 
 	tb->fmt = MNT_FMT_FSTAB;
diff --git a/libmount/src/utils.c b/libmount/src/utils.c
index 1fa67b85f4..e03d932651 100644
--- a/libmount/src/utils.c
+++ b/libmount/src/utils.c
@@ -100,6 +100,10 @@ static int fstype_cmp(const void *v1, const void *v2)
 	return strcmp(s1, s2);
 }
 
+/* This very simplified stat() alternative uses cached VFS data and does not
+ * directly ask the filesystem for details. It requires a kernel that supports
+ * statx(). It's usable only for file type, rdev and ino!
+ */
 static int safe_stat(const char *target, struct stat *st, int nofollow)
 {
 	assert(target);
@@ -125,26 +129,28 @@ static int safe_stat(const char *target, struct stat *st, int nofollow)
 		if (rc == 0) {
 			st->st_ino  = stx.stx_ino;
 			st->st_dev  = makedev(stx.stx_dev_major, stx.stx_dev_minor);
+			st->st_rdev = makedev(stx.stx_rdev_major, stx.stx_rdev_minor);
 			st->st_mode = stx.stx_mode;
 		}
-		return rc;
+
+		if (rc == 0 || errno != EOPNOTSUPP)
+			return rc;
 	}
-#else
-# ifdef AT_NO_AUTOMOUNT
+#endif
+
+#ifdef AT_NO_AUTOMOUNT
 	return fstatat(AT_FDCWD, target, st,
 			AT_NO_AUTOMOUNT | (nofollow ? AT_SYMLINK_NOFOLLOW : 0));
-# else
-	return nofollow ? lstat(target, st) : stat(target, st);
-# endif
 #endif
+	return nofollow ? lstat(target, st) : stat(target, st);
 }
 
-int mnt_stat_mountpoint(const char *target, struct stat *st)
+int mnt_safe_stat(const char *target, struct stat *st)
 {
 	return safe_stat(target, st, 0);
 }
 
-int mnt_lstat_mountpoint(const char *target, struct stat *st)
+int mnt_safe_lstat(const char *target, struct stat *st)
 {
 	return safe_stat(target, st, 1);
 }
@@ -1074,7 +1080,7 @@ char *mnt_get_mountpoint(const char *path)
 	if (*mnt == '/' && *(mnt + 1) == '\0')
 		goto done;
 
-	if (mnt_stat_mountpoint(mnt, &st))
+	if (mnt_safe_stat(mnt, &st))
 		goto err;
 	base = st.st_dev;
 
@@ -1083,7 +1089,7 @@ char *mnt_get_mountpoint(const char *path)
 
 		if (!p)
 			break;
-		if (mnt_stat_mountpoint(*mnt ? mnt : "/", &st))
+		if (mnt_safe_stat(*mnt ? mnt : "/", &st))
 			goto err;
 		dir = st.st_dev;
 		if (dir != base) {
@@ -1488,9 +1494,9 @@ static int tests_stat(struct libmnt_test *ts, int argc, char *argv[])
 	int rc;
 
 	if (strcmp(argv[0], "--lstat") == 0)
-		rc = mnt_lstat_mountpoint(path, &st);
+		rc = mnt_safe_lstat(path, &st);
 	else
-		rc = mnt_stat_mountpoint(path, &st);
+		rc = mnt_safe_stat(path, &st);
 	if (rc)
 		printf("%s: failed: rc=%d: %m\n", path, rc);
 	else {