[syslinux] fix Syslinux installation for some media

* Some disk devices, such as O2Micro PCI-E SD card readers, return ERROR_INVALID_PARAMETER
  when attempting to use ReadFile() on a volume against a non 8-byte aligned buffer.
* This patch ensures that the Syslinux buffers for sector patching are 16-byte aligned.
* HUGE THANKS to 424778940z, for the numerous testing that allowed to troubleshoot this issue.
* Closes #767

src/rufus.rc

@@ -33,7 +33,7 @@ LANGUAGE LANG_NEUTRAL, SUBLANG_NEUTRAL
 IDD_DIALOG DIALOGEX 12, 12, 242, 376
 STYLE DS_SETFONT | DS_MODALFRAME | DS_CENTER | WS_MINIMIZEBOX | WS_POPUP | WS_CAPTION | WS_SYSMENU
 EXSTYLE WS_EX_ACCEPTFILES
-CAPTION "Rufus 2.10.956"
+CAPTION "Rufus 2.10.957"
 FONT 8, "Segoe UI Symbol", 400, 0, 0x0
 BEGIN
     LTEXT           "Device",IDS_DEVICE_TXT,9,6,200,8
@@ -320,8 +320,8 @@ END
 //
 
 VS_VERSION_INFO VERSIONINFO
- FILEVERSION 2,10,956,0
+ FILEVERSION 2,10,957,0
- PRODUCTVERSION 2,10,956,0
+ PRODUCTVERSION 2,10,957,0
  FILEFLAGSMASK 0x3fL
 #ifdef _DEBUG
  FILEFLAGS 0x1L
@@ -338,13 +338,13 @@ BEGIN
         BEGIN
             VALUE "CompanyName", "Akeo Consulting (http://akeo.ie)"
             VALUE "FileDescription", "Rufus"
-            VALUE "FileVersion", "2.10.956"
+            VALUE "FileVersion", "2.10.957"
             VALUE "InternalName", "Rufus"
             VALUE "LegalCopyright", "© 2011-2016 Pete Batard (GPL v3)"
             VALUE "LegalTrademarks", "http://www.gnu.org/copyleft/gpl.html"
             VALUE "OriginalFilename", "rufus.exe"
             VALUE "ProductName", "Rufus"
-            VALUE "ProductVersion", "2.10.956"
+            VALUE "ProductVersion", "2.10.957"
         END
     END
     BLOCK "VarFileInfo"

src/syslinux.c

@@ -105,18 +105,19 @@ BOOL InstallSyslinux(DWORD drive_index, char drive_letter, int fs_type)
 	const char* ldlinux_ext[3] = { "sys", "bss", "c32" };
 	const char* mboot_c32 = "mboot.c32";
 	char path[MAX_PATH], tmp[64];
+	const char *errmsg;
 	struct libfat_filesystem *fs;
 	libfat_sector_t s, *secp;
 	libfat_sector_t *sectors = NULL;
 	int ldlinux_sectors;
 	uint32_t ldlinux_cluster;
-	int i, nsectors;
+	int i, nsectors, sl_fs_stype;
 	int bt = (int)ComboBox_GetItemData(hBootType, ComboBox_GetCurSel(hBootType));
 	BOOL use_v5 = (bt == BT_SYSLINUX_V6) || ((bt == BT_ISO) && (SL_MAJOR(img_report.sl_version) >= 5));
 
 	PrintInfoDebug(0, MSG_234, (bt == BT_ISO)?img_report.sl_version_str:embedded_sl_version_str[use_v5?1:0]);
 
-	// 4K sector size workaround
+	/* 4K sector size workaround */
 	SECTOR_SHIFT = 0;
 	SECTOR_SIZE = SelectedDrive.SectorSize;
 	while (SECTOR_SIZE>>=1)
@@ -126,10 +127,32 @@ BOOL InstallSyslinux(DWORD drive_index, char drive_letter, int fs_type)
 	LIBFAT_SECTOR_SIZE = SECTOR_SIZE;
 	LIBFAT_SECTOR_MASK = SECTOR_SIZE - 1;
 
-	sectbuf = malloc(SECTOR_SIZE);
+	/* sectbuf should be aligned to at least 8 bytes - see github #767 */
+	sectbuf = _aligned_malloc(SECTOR_SIZE, 16);
 	if (sectbuf == NULL)
 		goto out;
 
+	/* First, reopen the volume (we already have a lock) */
+	d_handle = GetLogicalHandle(drive_index, TRUE, FALSE);
+	if ((d_handle == INVALID_HANDLE_VALUE) || (d_handle == NULL)) {
+		uprintf("Could open volume for Syslinux installation");
+		goto out;
+	}
+
+	/* Make sure we can read the boot sector (NB: Re-open already set us to offset 0) */
+	if (!ReadFile(d_handle, sectbuf, SECTOR_SIZE, &bytes_read, NULL)) {
+		uprintf("Could not read VBR");
+		goto out;
+	}
+	if (bytes_read != SECTOR_SIZE) {
+		uprintf("Could not read the whole VBR");
+		goto out;
+	}
+	if ((errmsg = syslinux_check_bootsect(sectbuf, &sl_fs_stype))) {
+		uprintf("Error: %s", errmsg);
+		goto out;
+	}
+
 	/* Initialize the ADV -- this should be smarter */
 	syslinux_reset_adv(syslinux_adv);
 
@@ -201,13 +224,6 @@ BOOL InstallSyslinux(DWORD drive_index, char drive_letter, int fs_type)
 		goto out;
 	}
 
-	/* Reopen the volume (we already have a lock) */
-	d_handle = GetLogicalHandle(drive_index, TRUE, FALSE);
-	if ((d_handle == INVALID_HANDLE_VALUE) || (d_handle == NULL)) {
-		uprintf("Could open volume for Syslinux installation");
-		goto out;
-	}
-
 	/* Map the file (is there a better way to do this?) */
 	ldlinux_sectors = (syslinux_ldlinux_len[0] + 2 * ADV_SIZE + SECTOR_SIZE - 1) >> SECTOR_SHIFT;
 	sectors = (libfat_sector_t*) calloc(ldlinux_sectors, sizeof *sectors);
@@ -366,7 +382,8 @@ BOOL InstallSyslinux(DWORD drive_index, char drive_letter, int fs_type)
 	r = TRUE;
 
 out:
-	safe_free(sectbuf);
+	if (sectbuf != NULL)
+		_aligned_free(sectbuf);
 	safe_free(syslinux_ldlinux[0]);
 	safe_free(syslinux_ldlinux[1]);
 	safe_free(sectors);

src/syslinux/libfat/cache.c

@@ -19,6 +19,20 @@
 #include <stdlib.h>
 #include "libfatint.h"
 
+/*
+ * We need to align our sector buffers to at least the 8-byte mark, as some Windows
+ * disk devices, notably O2Micro PCI-E SD card readers, return ERROR_INVALID_PARAMETER
+ * when attempting to use ReadFile() against a non 8-byte aligned buffer.
+ * For good measure, we'll go further and align our buffers on a 16-byte boundary.
+ * Also, since struct libfat_sector's data[0] is our buffer, this means we must BOTH
+ * align that member in the struct declaration, and use aligned malloc/free.
+ */
+#if defined(__MINGW32__)
+#define _aligned_malloc                 __mingw_aligned_malloc
+#define _aligned_free                   __mingw_aligned_free
+#endif
+
+extern void _uprintf(const char *format, ...);
 void *libfat_get_sector(struct libfat_filesystem *fs, libfat_sector_t n)
 {
     struct libfat_sector *ls;
@@ -29,10 +43,10 @@ void *libfat_get_sector(struct libfat_filesystem *fs, libfat_sector_t n)
     }
 
     /* Not found in cache */
-    ls = malloc(sizeof(struct libfat_sector) + LIBFAT_SECTOR_SIZE);
+    ls = _aligned_malloc(sizeof(struct libfat_sector) + LIBFAT_SECTOR_SIZE, 16);
     if (!ls) {
 	libfat_flush(fs);
-	ls = malloc(sizeof(struct libfat_sector) + LIBFAT_SECTOR_SIZE);
+	ls = _aligned_malloc(sizeof(struct libfat_sector) + LIBFAT_SECTOR_SIZE, 16);
 
 	if (!ls)
 	    return NULL;	/* Can't allocate memory */
@@ -40,7 +54,7 @@ void *libfat_get_sector(struct libfat_filesystem *fs, libfat_sector_t n)
 
     if (fs->read(fs->readptr, ls->data, LIBFAT_SECTOR_SIZE, n)
 	!= LIBFAT_SECTOR_SIZE) {
-	free(ls);
+	_aligned_free(ls);
 	return NULL;		/* I/O error */
     }
 
@@ -60,6 +74,6 @@ void libfat_flush(struct libfat_filesystem *fs)
 
     for (ls = lsnext; ls; ls = lsnext) {
 	lsnext = ls->next;
-	free(ls);
+	_aligned_free(ls);
     }
 }

src/syslinux/libfat/libfatint.h

@@ -22,10 +22,19 @@
 #include "libfat.h"
 #include "fat.h"
 
+#if defined(__GNUC__)
+#define ALIGN_START(m)
+#define ALIGN_END(m) __attribute__ ((__aligned__(m)))
+#elif defined(_MSC_VER)
+#define ALIGN_START(m) __declspec(align(m))
+#define ALIGN_END(m)
+#endif
+
 struct libfat_sector {
-    libfat_sector_t n;		/* Sector number */
+	libfat_sector_t n;		/* Sector number */
-    struct libfat_sector *next;	/* Next in list */
+	struct libfat_sector *next;	/* Next in list */
-    char data[0];
+	/* data[0] MUST be aligned to at least 8 bytes - see cache.c */
+	ALIGN_START(16) char data[0] ALIGN_END(16);
 };
 
 enum fat_type {