diff options
| -rw-r--r-- | util-linux/mkfs_vfat.c | 12 |
1 files changed, 9 insertions, 3 deletions
diff --git a/util-linux/mkfs_vfat.c b/util-linux/mkfs_vfat.c index 10de2af5b..de88a7443 100644 --- a/util-linux/mkfs_vfat.c +++ b/util-linux/mkfs_vfat.c @@ -391,16 +391,22 @@ int mkfs_vfat_main(int argc UNUSED_PARAM, char **argv) while (1) { while (1) { int spf_adj; - off_t tcl = (volume_size_sect - reserved_sect - NUM_FATS * sect_per_fat) / sect_per_clust; + uoff_t tcl = (volume_size_sect - reserved_sect - NUM_FATS * sect_per_fat) / sect_per_clust; // tcl may be > MAX_CLUST_32 here, but it may be // because sect_per_fat is underestimated, // and with increased sect_per_fat it still may become // <= MAX_CLUST_32. Therefore, we do not check // against MAX_CLUST_32, but against a bigger const: - if (tcl > 0x7fffffff) + if (tcl > 0x80ffffff) goto next; total_clust = tcl; // fits in uint32_t - spf_adj = ((total_clust + 2) * 4 + bytes_per_sect - 1) / bytes_per_sect - sect_per_fat; + // Every cluster needs 4 bytes in FAT. +2 entries since + // FAT has space for non-existent clusters 0 and 1. + // Let's see how many sectors that needs. + //May overflow at "*4": + //spf_adj = ((total_clust+2) * 4 + bytes_per_sect-1) / bytes_per_sect - sect_per_fat; + //Same in the more obscure, non-overflowing form: + spf_adj = ((total_clust+2) + (bytes_per_sect/4)-1) / (bytes_per_sect/4) - sect_per_fat; #if 0 bb_error_msg("sect_per_clust:%u sect_per_fat:%u total_clust:%u", sect_per_clust, sect_per_fat, (int)tcl); |