146 lines
4.3 KiB
Diff
146 lines
4.3 KiB
Diff
diff --git a/fs/fat/Kconfig b/fs/fat/Kconfig
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index 182f9ff..907a5de 100644
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--- a/fs/fat/Kconfig
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+++ b/fs/fat/Kconfig
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@@ -74,6 +74,26 @@ config VFAT_FS
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To compile this as a module, choose M here: the module will be called
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vfat.
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+config VFAT_FS_DUALNAMES
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+ bool "VFAT dual names support"
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+ depends on VFAT_FS
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+ help
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+ This option provides support for dual filenames on VFAT filesystems.
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+ If this option is disabled then file creation will either put
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+ a short (8.3) name or a long name on the file, but never both.
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+ The field where a shortname would normally go is filled with
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+ invalid characters such that it cannot be considered a valid
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+ short filename.
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+
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+ That means that long filenames created with this option
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+ disabled will not be accessible at all to operating systems
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+ that do not understand the VFAT extensions.
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+
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+ Users considering enabling this option should consider the implications
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+ of any patents that may exist on dual filenames in VFAT.
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+
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+ If unsure, say N
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+
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config FAT_DEFAULT_CODEPAGE
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int "Default codepage for FAT"
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depends on MSDOS_FS || VFAT_FS
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diff --git a/fs/fat/dir.c b/fs/fat/dir.c
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index 38ff75a..cd5d3ec 100644
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--- a/fs/fat/dir.c
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+++ b/fs/fat/dir.c
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@@ -415,14 +415,13 @@
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}
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i += chl;
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}
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- if (!last_u)
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- continue;
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-
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- /* Compare shortname */
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- bufuname[last_u] = 0x0000;
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- len = fat_uni_to_x8(sb, bufuname, bufname, sizeof(bufname));
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- if (fat_name_match(sbi, name, name_len, bufname, len))
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- goto found;
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+ if (last_u) {
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+ /* Compare shortname */
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+ bufuname[last_u] = 0x0000;
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+ len = fat_uni_to_x8(sb, bufuname, bufname, sizeof(bufname));
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+ if (fat_name_match(sbi, name, name_len, bufname, len))
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+ goto found;
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+ }
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if (nr_slots) {
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void *longname = unicode + FAT_MAX_UNI_CHARS;
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diff --git a/fs/fat/namei_vfat.c b/fs/fat/namei_vfat.c
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index 73471b7..894f44d 100644
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--- a/fs/fat/namei_vfat.c
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+++ b/fs/fat/namei_vfat.c
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@@ -22,6 +22,7 @@
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#include <linux/smp_lock.h>
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#include <linux/buffer_head.h>
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#include <linux/namei.h>
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+#include <linux/random.h>
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#include "fat.h"
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/*
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@@ -586,6 +587,59 @@ xlate_to_uni(const unsigned char *name, int len, unsigned char *outname,
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return 0;
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}
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+#ifndef CONFIG_VFAT_FS_DUALNAMES
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+/*
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+ * build a 11 byte 8.3 buffer which is not a short filename. We want 11
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+ * bytes which:
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+ * - will be seen as a constant string to all APIs on Linux and Windows
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+ * - cannot be matched with wildcard patterns
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+ * - cannot be used to access the file
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+ * - has a low probability of collision within a directory
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+ * - has an invalid 3 byte extension
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+ * - contains at least one non-space and non-nul byte
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+ */
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+static void vfat_build_dummy_83_buffer(struct inode *dir, char *msdos_name)
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+{
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+ u32 rand_num = random32() & 0x3FFFFFFF;
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+ int i;
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+
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+ /* a value of zero would leave us with only nul and spaces,
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+ * which would not work with older linux systems
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+ */
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+ if (rand_num == 0)
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+ rand_num = 1;
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+
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+ /* we start with a space followed by nul as spaces at the
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+ * start of an entry are trimmed in FAT, which means that
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+ * starting the 11 bytes with 0x20 0x00 gives us a value which
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+ * cannot be used to access the file. It also means that the
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+ * value as seen from all Windows and Linux APIs is a constant
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+ */
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+ msdos_name[0] = ' ';
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+ msdos_name[1] = 0;
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+
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+ /* we use / and 2 nul bytes for the extension. These are
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+ * invalid in FAT and mean that utilities that show the
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+ * directory show no extension, but still work via the long
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+ * name for old Linux kernels
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+ */
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+ msdos_name[8] = '/';
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+ msdos_name[9] = 0;
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+ msdos_name[10] = 0;
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+
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+ /*
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+ * fill the remaining 6 bytes with random invalid values
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+ * This gives us a low collision rate, which means a low
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+ * chance of problems with chkdsk.exe and WindowsXP
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+ */
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+ for (i = 2; i < 8; i++) {
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+ msdos_name[i] = rand_num & 0x1F;
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+ rand_num >>= 5;
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+ }
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+}
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+#endif
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+
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+
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static int vfat_build_slots(struct inode *dir, const unsigned char *name,
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int len, int is_dir, int cluster,
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struct timespec *ts,
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@@ -628,6 +682,11 @@ static int vfat_build_slots(struct inode *dir, const unsigned char *name,
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goto shortname;
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}
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+#ifndef CONFIG_VFAT_FS_DUALNAMES
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+ vfat_build_dummy_83_buffer(dir, msdos_name);
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+ lcase = 0;
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+#endif
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+
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/* build the entry of long file name */
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cksum = fat_checksum(msdos_name);
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--
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1.6.0.4
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