1 files changed, 52 insertions, 17 deletions

diff --git a/fs/qnx4/dir.c b/fs/qnx4/dir.c
index b218f965817b..613cc38c9efa 100644
--- a/fs/qnx4/dir.c
+++ b/fs/qnx4/dir.c
@@ -14,13 +14,48 @@
 #include <linux/buffer_head.h>
 #include "qnx4.h"
 
+/*
+ * A qnx4 directory entry is an inode entry or link info
+ * depending on the status field in the last byte. The
+ * first byte is where the name start either way, and a
+ * zero means it's empty.
+ *
+ * Also, due to a bug in gcc, we don't want to use the
+ * real (differently sized) name arrays in the inode and
+ * link entries, but always the 'de_name[]' one in the
+ * fake struct entry.
+ *
+ * See
+ *
+ *   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578#c6
+ *
+ * for details, but basically gcc will take the size of the
+ * 'name' array from one of the used union entries randomly.
+ *
+ * This use of 'de_name[]' (48 bytes) avoids the false positive
+ * warnings that would happen if gcc decides to use 'inode.di_name'
+ * (16 bytes) even when the pointer and size were to come from
+ * 'link.dl_name' (48 bytes).
+ *
+ * In all cases the actual name pointer itself is the same, it's
+ * only the gcc internal 'what is the size of this field' logic
+ * that can get confused.
+ */
+union qnx4_directory_entry {
+	struct {
+		const char de_name[48];
+		u8 de_pad[15];
+		u8 de_status;
+	};
+	struct qnx4_inode_entry inode;
+	struct qnx4_link_info link;
+};
+
 static int qnx4_readdir(struct file *file, struct dir_context *ctx)
 {
 	struct inode *inode = file_inode(file);
 	unsigned int offset;
 	struct buffer_head *bh;
-	struct qnx4_inode_entry *de;
-	struct qnx4_link_info *le;
 	unsigned long blknum;
 	int ix, ino;
 	int size;
@@ -37,27 +72,27 @@ static int qnx4_readdir(struct file *file, struct dir_context *ctx)
 		}
 		ix = (ctx->pos >> QNX4_DIR_ENTRY_SIZE_BITS) % QNX4_INODES_PER_BLOCK;
 		for (; ix < QNX4_INODES_PER_BLOCK; ix++, ctx->pos += QNX4_DIR_ENTRY_SIZE) {
+			union qnx4_directory_entry *de;
+
 			offset = ix * QNX4_DIR_ENTRY_SIZE;
-			de = (struct qnx4_inode_entry *) (bh->b_data + offset);
-			if (!de->di_fname[0])
+			de = (union qnx4_directory_entry *) (bh->b_data + offset);
+
+			if (!de->de_name[0])
 				continue;
-			if (!(de->di_status & (QNX4_FILE_USED|QNX4_FILE_LINK)))
+			if (!(de->de_status & (QNX4_FILE_USED|QNX4_FILE_LINK)))
 				continue;
-			if (!(de->di_status & QNX4_FILE_LINK))
-				size = QNX4_SHORT_NAME_MAX;
-			else
-				size = QNX4_NAME_MAX;
-			size = strnlen(de->di_fname, size);
-			QNX4DEBUG((KERN_INFO "qnx4_readdir:%.*s\n", size, de->di_fname));
-			if (!(de->di_status & QNX4_FILE_LINK))
+			if (!(de->de_status & QNX4_FILE_LINK)) {
+				size = sizeof(de->inode.di_fname);
 				ino = blknum * QNX4_INODES_PER_BLOCK + ix - 1;
-			else {
-				le  = (struct qnx4_link_info*)de;
-				ino = ( le32_to_cpu(le->dl_inode_blk) - 1 ) *
+			} else {
+				size = sizeof(de->link.dl_fname);
+				ino = ( le32_to_cpu(de->link.dl_inode_blk) - 1 ) *
 					QNX4_INODES_PER_BLOCK +
-					le->dl_inode_ndx;
+					de->link.dl_inode_ndx;
 			}
-			if (!dir_emit(ctx, de->di_fname, size, ino, DT_UNKNOWN)) {
+			size = strnlen(de->de_name, size);
+			QNX4DEBUG((KERN_INFO "qnx4_readdir:%.*s\n", size, name));
+			if (!dir_emit(ctx, de->de_name, size, ino, DT_UNKNOWN)) {
 				brelse(bh);
 				return 0;
 			}