fat: Add disable VFAT dual names support from Sony kernel (5dfab3c0) · Commits · e / devices / android_kernel_sony_msm8998

fs/fat/Kconfig

+21 −0

Original line number	Diff line number	Diff line
		@@ -74,6 +74,27 @@ config VFAT_FS
		To compile this as a module, choose M here: the module will be called
		vfat.

		config VFAT_FS_NO_DUALNAMES
		bool "disable VFAT dual names support (patent workaround)"
		depends on VFAT_FS
		help
		This option disables support for dual filenames on VFAT filesystems.
		If this option is enabled then file creation will either put
		a short (8.3) name or a long name on the file, but never both.
		The field where a shortname would normally go is filled with
		invalid characters such that it cannot be considered a valid
		short filename.

		That means that long filenames created with this option
		disabled will not be accessible at all to operating systems
		that do not understand the FAT long filename extensions.

		Users considering disabling this option should consider the
		implications of any patents that may exist on dual filenames
		in VFAT.

		If unsure, say N

		config FAT_DEFAULT_CODEPAGE
		int "Default codepage for FAT"
		depends on MSDOS_FS \|\| VFAT_FS

fs/fat/dir.c

+14 −0

Original line number	Diff line number	Diff line
		@@ -498,6 +498,13 @@ parse_record:
		goto end_of_dir;
		}

		/*
		* The FAT_NO_83NAME flag is used to mark files
		* created with no 8.3 short name
		*/
		if (de->lcase & FAT_NO_83NAME)
		goto compare_longname;

		/* Never prepend '.' to hidden files here.
		* That is done only for msdos mounts (and only when
		* 'dotsOK=yes'); if we are executing here, it is in the
		@@ -511,6 +518,7 @@ parse_record:
		if (fat_name_match(sbi, name, name_len, bufname, len))
		goto found;

		compare_longname:
		if (nr_slots) {
		void *longname = unicode + FAT_MAX_UNI_CHARS;
		int size = PATH_MAX - FAT_MAX_UNI_SIZE;
		@@ -602,6 +610,8 @@ parse_record:
		if (de->attr != ATTR_EXT && IS_FREE(de->name))
		goto record_end;
		} else {
		if (de->lcase & FAT_NO_83NAME)
		goto record_end;
		if ((de->attr & ATTR_VOLUME) \|\| IS_FREE(de->name))
		goto record_end;
		}
		@@ -960,6 +970,10 @@ int fat_scan(struct inode dir, const unsigned char name,
		sinfo->bh = NULL;
		while (fat_get_short_entry(dir, &sinfo->slot_off, &sinfo->bh,
		&sinfo->de) >= 0) {
		/* skip files marked as having no 8.3 short name */
		if (sinfo->de->lcase & FAT_NO_83NAME)
		continue;

		if (!strncmp(sinfo->de->name, name, MSDOS_NAME)) {
		sinfo->slot_off -= sizeof(*sinfo->de);
		sinfo->nr_slots = 1;

fs/fat/namei_vfat.c

+81 −2

Original line number	Diff line number	Diff line
		@@ -20,6 +20,7 @@
		#include <linux/slab.h>
		#include <linux/namei.h>
		#include "fat.h"
		#include <linux/random.h>

		/*
		* If new entry was created in the parent, it could create the 8.3
		@@ -322,6 +323,17 @@ static int vfat_create_shortname(struct inode dir, struct nls_table nls,
		int sz = 0, extlen, baselen, i, numtail_baselen, numtail2_baselen;
		int is_shortname;
		struct shortname_info base_info, ext_info;
		unsigned opts_shortname = opts->shortname;

		#ifdef CONFIG_VFAT_FS_NO_DUALNAMES
		/*
		* When we do not have dualnames, we want to maximise the
		* chance that a file will be able to be represented with just
		* a 8.3 entry. We can do that by using the WINNT case
		* handling extensions to FAT.
		*/
		opts_shortname = VFAT_SFN_CREATE_WINNT;
		#endif

		is_shortname = 1;
		INIT_SHORTNAME_INFO(&base_info);
		@@ -434,9 +446,9 @@ static int vfat_create_shortname(struct inode dir, struct nls_table nls,
		if (vfat_find_form(dir, name_res) == 0)
		return -EEXIST;

		if (opts->shortname & VFAT_SFN_CREATE_WIN95) {
		if (opts_shortname & VFAT_SFN_CREATE_WIN95) {
		return (base_info.upper && ext_info.upper);
		} else if (opts->shortname & VFAT_SFN_CREATE_WINNT) {
		} else if (opts_shortname & VFAT_SFN_CREATE_WINNT) {
		if ((base_info.upper \|\| base_info.lower) &&
		(ext_info.upper \|\| ext_info.lower)) {
		if (!base_info.upper && base_info.lower)
		@@ -575,6 +587,66 @@ xlate_to_uni(const unsigned char name, int len, unsigned char outname,
		return 0;
		}

		#ifdef CONFIG_VFAT_FS_NO_DUALNAMES
		/*
		* This function creates a dummy 8.3 entry which is as compatible as
		* possible with existing FAT devices, while not being a valid
		* filename under windows or Linux
		*/
		static void vfat_build_dummy_83_buffer(struct inode dir, char msdos_name,
		int is_dir)
		{
		/*
		* These characters are all invalid in 8.3 names, plus have
		* been shown to be harmless on all tested devices
		*/
		const char invalidchar[] = { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x0B,
		0x0C, 0x0E, 0x0F, 0x10, 0x11, 0x12, 0x13,
		0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A,
		0x1B, 0x1C, 0x1D, 0x1E, 0x1F, 0x22, 0x2a,
		0x3a, 0x3c, 0x3e, 0x3f, 0x5b, 0x5d, 0x7c };
		int i, tilde_pos, slash_pos;
		u32 rand_num = prandom_u32();

		/* We need a '~' in the prefix to make Win98 happy. */
		tilde_pos = rand_num % 8;
		rand_num >>= 3;

		/*
		* the '/' makes sure that even unpatched Linux systems can't
		* get at files by the 8.3 entry. Don't put in a / in
		* directories as it can cause problems with some
		* photo frames
		*/
		if (is_dir)
		slash_pos = -1;
		else {
		slash_pos = (tilde_pos + 1 + rand_num % 7) % 8;
		rand_num >>= 3;
		}

		/*
		* fill in the first 8 bytes with invalid characters. Note
		* that we need to be careful not to run out of randomness. We
		* leave the 3 byte extension in place as some cheap MP3
		* players need them.
		*/
		for (i = 0; i < 8; i++) {
		if (i == tilde_pos)
		msdos_name[i] = '~';
		else if (i == slash_pos)
		msdos_name[i] = '/';
		else {
		msdos_name[i] =
		invalidchar[rand_num % sizeof(invalidchar)];
		rand_num /= sizeof(invalidchar);
		if (rand_num < sizeof(invalidchar))
		rand_num = prandom_u32();
		}
		}
		}
		#endif

		static int vfat_build_slots(struct inode dir, const unsigned char name,
		int len, int is_dir, int cluster,
		struct timespec *ts,
		@@ -617,6 +689,13 @@ static int vfat_build_slots(struct inode dir, const unsigned char name,
		goto shortname;
		}

		#ifdef CONFIG_VFAT_FS_NO_DUALNAMES
		printk_once(KERN_INFO
		"VFAT: not creating 8.3 short filenames for long names\n");
		vfat_build_dummy_83_buffer(dir, msdos_name, is_dir);
		lcase = FAT_NO_83NAME;
		#endif

		/* build the entry of long file name */
		cksum = fat_checksum(msdos_name);

include/uapi/linux/msdos_fs.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -45,6 +45,7 @@

		#define CASE_LOWER_BASE 8 /* base is lower case */
		#define CASE_LOWER_EXT 16 /* extension is lower case */
		#define FAT_NO_83NAME 32 /* no 8.3 short filename for this file */

		#define DELETED_FLAG 0xe5 /* marks file as deleted when in name[0] */
		#define IS_FREE(n) (!(n) \|\| (n) == DELETED_FLAG)