Hi,
This patch makes detection of a FAT filesystem more exact than current
one by checking the first entry of FAT.
Please apply.
-- OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>diff -urN fat_chain_error-2.5.9/fs/fat/cache.c fat_check_FAT-2.5.9/fs/fat/cache.c --- fat_chain_error-2.5.9/fs/fat/cache.c Thu Apr 25 01:33:58 2002 +++ fat_check_FAT-2.5.9/fs/fat/cache.c Thu Apr 25 01:38:44 2002 @@ -34,16 +34,12 @@ return MSDOS_SB(inode->i_sb)->cvf_format->cvf_bmap(inode,sector); } -int default_fat_access(struct super_block *sb,int nr,int new_value) +int __fat_access(struct super_block *sb, int nr, int new_value) { struct buffer_head *bh, *bh2, *c_bh, *c_bh2; unsigned char *p_first, *p_last; int copy, first, last, next, b; - if (nr < 2 || MSDOS_SB(sb)->clusters + 2 <= nr) { - fat_fs_panic(sb, "invalid access to FAT (entry 0x%08x)", nr); - return -EIO; - } if (MSDOS_SB(sb)->fat_bits == 32) { first = last = nr*4; } else if (MSDOS_SB(sb)->fat_bits == 16) { @@ -73,25 +69,17 @@ (sb->s_blocksize - 1)) >> 2]); /* Fscking Microsoft marketing department. Their "32" is 28. */ next &= 0x0fffffff; - if (next >= BAD_FAT32) next = FAT_ENT_EOF; - PRINTK(("fat_bread: 0x%x, nr=0x%x, first=0x%x, next=0x%x\n", b, nr, first, next)); - } else if (MSDOS_SB(sb)->fat_bits == 16) { p_first = p_last = NULL; /* GCC needs that stuff */ next = CF_LE_W(((__u16 *) bh->b_data)[(first & (sb->s_blocksize - 1)) >> 1]); - if (next >= BAD_FAT16) next = FAT_ENT_EOF; } else { p_first = &((__u8 *)bh->b_data)[first & (sb->s_blocksize - 1)]; p_last = &((__u8 *)bh2->b_data)[(first + 1) & (sb->s_blocksize - 1)]; if (nr & 1) next = ((*p_first >> 4) | (*p_last << 4)) & 0xfff; else next = (*p_first+(*p_last << 8)) & 0xfff; - if (next >= BAD_FAT12) next = FAT_ENT_EOF; } if (new_value != -1) { - if (next == FAT_ENT_EOF) - next = EOF_FAT(sb); - if (MSDOS_SB(sb)->fat_bits == 32) { ((__u32 *)bh->b_data)[(first & (sb->s_blocksize - 1)) >> 2] = CT_LE_L(new_value); @@ -132,6 +120,27 @@ fat_brelse(sb, bh); if (bh != bh2) fat_brelse(sb, bh2); + return next; +} + +int default_fat_access(struct super_block *sb, int nr, int new_value) +{ + int next; + + next = -EIO; + if (nr < 2 || MSDOS_SB(sb)->clusters + 2 <= nr) { + fat_fs_panic(sb, "invalid access to FAT (entry 0x%08x)", nr); + goto out; + } + if (new_value == FAT_ENT_EOF) + new_value = EOF_FAT(sb); + + next = __fat_access(sb, nr, new_value); + if (next < 0) + goto out; + if (next >= BAD_FAT(sb)) + next = FAT_ENT_EOF; +out: return next; } diff -urN fat_chain_error-2.5.9/fs/fat/inode.c fat_check_FAT-2.5.9/fs/fat/inode.c --- fat_chain_error-2.5.9/fs/fat/inode.c Thu Apr 25 01:33:58 2002 +++ fat_check_FAT-2.5.9/fs/fat/inode.c Thu Apr 25 01:38:44 2002 @@ -591,8 +591,9 @@ struct buffer_head *bh; struct fat_boot_sector *b; struct msdos_sb_info *sbi; - int logical_sector_size, fat_clusters, debug, cp; + int logical_sector_size, fat_clusters, debug, cp, first; unsigned int total_sectors, rootdir_sectors; + unsigned char media; long error = -EIO; char buf[50]; int i; @@ -655,6 +656,13 @@ brelse(bh); goto out_invalid; } + media = b->media; + if (!FAT_VALID_MEDIA(media)) { + if (!silent) + printk("FAT: invalid media value (0x%02x)\n", media); + brelse(bh); + goto out_invalid; + } logical_sector_size = CF_LE_W(get_unaligned((unsigned short *) &b->sector_size)); if (!logical_sector_size @@ -776,6 +784,21 @@ sbi->clusters = fat_clusters - 2; brelse(bh); + + /* validity check of FAT */ + first = __fat_access(sb, 0, -1); + if (first < 0) { + error = first; + goto out_fail; + } + if (FAT_FIRST_ENT(sb, media) != first) { + if (!silent) { + printk("FAT: invalid first entry of FAT " + "(0x%x != 0x%x)\n", + FAT_FIRST_ENT(sb, media), first); + } + goto out_invalid; + } if (!strcmp(cvf_format, "none")) i = -1; diff -urN fat_chain_error-2.5.9/include/linux/msdos_fs.h fat_check_FAT-2.5.9/include/linux/msdos_fs.h --- fat_chain_error-2.5.9/include/linux/msdos_fs.h Thu Apr 25 01:33:58 2002 +++ fat_check_FAT-2.5.9/include/linux/msdos_fs.h Thu Apr 25 01:38:44 2002 @@ -54,6 +54,11 @@ #define MSDOS_FAT12 4084 /* maximum number of clusters in a 12 bit FAT */ +/* media of boot sector */ +#define FAT_VALID_MEDIA(x) ((0xF8 <= (x) && (x) <= 0xFF) || (x) == 0xF0) +#define FAT_FIRST_ENT(s, x) ((MSDOS_SB(s)->fat_bits == 32 ? 0x0FFFFF00 : \ + MSDOS_SB(s)->fat_bits == 16 ? 0xFF00 : 0xF00) | (x)) + /* bad cluster mark */ #define BAD_FAT12 0xFF7 #define BAD_FAT16 0xFFF7 @@ -114,7 +119,7 @@ __u8 fats; /* number of FATs */ __u8 dir_entries[2]; /* root directory entries */ __u8 sectors[2]; /* number of sectors */ - __u8 media; /* media code (unused) */ + __u8 media; /* media code */ __u16 fat_length; /* sectors/FAT */ __u16 secs_track; /* sectors per track */ __u16 heads; /* number of heads */ @@ -242,6 +247,7 @@ /* fat/cache.c */ extern int fat_access(struct super_block *sb, int nr, int new_value); +extern int __fat_access(struct super_block *sb, int nr, int new_value); extern int fat_bmap(struct inode *inode, int sector); extern void fat_cache_init(void); extern void fat_cache_lookup(struct inode *inode, int cluster, int *f_clu, - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Tue Apr 30 2002 - 22:00:11 EST