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Correcting miscalculation of sector number in some cases.

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mkdosfs will incorrectly calculate the number of sectors of a
given FAT partition if the number sectors are odd due to
count_blocks incorrectly handling the remainder of a division
operation. This miscalculation causes the OMAP4 bootloader to
fail to boot.

This bug can be observed by comparing the total sector size in
fdisk expert more to fsck.msdos; this discrepancy only shows up
when the number of sectors are odd.

See https://bugs.launchpad.net/ubuntu/+source/dosfstools/+bug/794043
for more information.

Signed-off-by: Daniel Baumann <mail@daniel-baumann.ch>
This commit is contained in:
Michael Casadevall 2011-06-07 19:19:30 +02:00 committed by Daniel Baumann
parent 91a1fb9536
commit 025b4f04fe
1 changed files with 9 additions and 5 deletions
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14
src/mkdosfs.c
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@ -305,6 +305,7 @@ static char *blank_sector; /* Blank sector - all zeros */
static int hidden_sectors = 0; /* Number of hidden sectors */ static int hidden_sectors = 0; /* Number of hidden sectors */
static int malloc_entire_fat = FALSE; /* Whether we should malloc() the entire FAT or not */ static int malloc_entire_fat = FALSE; /* Whether we should malloc() the entire FAT or not */
static int align_structures = TRUE; /* Whether to enforce alignment */ static int align_structures = TRUE; /* Whether to enforce alignment */
static int orphaned_sectors = 0; /* Sectors that exist in the last block of filesystem */
/* Function prototype definitions */ /* Function prototype definitions */
@ -316,7 +317,7 @@ static void alarm_intr(int alnum);
static void check_blocks(void); static void check_blocks(void);
static void get_list_blocks(char *filename); static void get_list_blocks(char *filename);
static int valid_offset(int fd, loff_t offset); static int valid_offset(int fd, loff_t offset);
static unsigned long long count_blocks(char *filename); static unsigned long long count_blocks(char *filename, int *remainder);
static void check_mount(char *device_name); static void check_mount(char *device_name);
static void establish_params(int device_num, int size); static void establish_params(int device_num, int size);
static void setup_tables(void); static void setup_tables(void);
@ -503,7 +504,8 @@ static int valid_offset(int fd, loff_t offset)
/* Given a filename, look to see how many blocks of BLOCK_SIZE are present, returning the answer */ /* Given a filename, look to see how many blocks of BLOCK_SIZE are present, returning the answer */
static unsigned long long count_blocks(char *filename) static unsigned long long count_blocks(char *filename, int *remainder)
{ {
loff_t high, low; loff_t high, low;
int fd; int fd;
@ -529,7 +531,8 @@ static unsigned long long count_blocks(char *filename)
} }
close(fd); close(fd);
return low / BLOCK_SIZE; *remainder = (low%BLOCK_SIZE)/sector_size;
return(low / BLOCK_SIZE);
} }
/* Check to see if the specified device is currently mounted - abort if it is */ /* Check to see if the specified device is currently mounted - abort if it is */
@ -829,7 +832,8 @@ static void setup_tables(void)
memcpy(&bs.hidden, &hidden, 2); memcpy(&bs.hidden, &hidden, 2);
} }
num_sectors = (long long)blocks *BLOCK_SIZE / sector_size; num_sectors = (long long)(blocks *BLOCK_SIZE / sector_size)+orphaned_sectors;
if (!atari_format) { if (!atari_format) {
unsigned fatdata1216; /* Sectors for FATs + data area (FAT12/16) */ unsigned fatdata1216; /* Sectors for FATs + data area (FAT12/16) */
unsigned fatdata32; /* Sectors for FATs + data area (FAT32) */ unsigned fatdata32; /* Sectors for FATs + data area (FAT32) */
@ -1617,7 +1621,7 @@ int main(int argc, char **argv)
} }
if (!create) if (!create)
cblocks = count_blocks(device_name); /* Have a look and see! */ cblocks = count_blocks(device_name, &orphaned_sectors); /* Have a look and see! */
} }
if (optind == argc - 2) { /* Either check the user specified number */ if (optind == argc - 2) { /* Either check the user specified number */
blocks = strtoull(argv[optind + 1], &tmp, 0); blocks = strtoull(argv[optind + 1], &tmp, 0);