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fs/fat: Address missing bpb validity checks. Fixes #351 and #352

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mintsuki 2024-05-22 04:44:11 +02:00
parent 59ac73d753
commit 5b1cd9d01b
1 changed files with 29 additions and 4 deletions
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33
common/fs/fat32.s2.c
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@ -104,24 +104,49 @@ static int fat32_init_context(struct fat32_context* context, struct volume *part
struct fat32_bpb bpb;
volume_read(context->part, &bpb, 0, sizeof(struct fat32_bpb));
// Sanity check of bpb
// Checks for FAT12/16
if (strncmp((((void *)&bpb) + 0x36), "FAT", 3) == 0) {
goto valid;
goto signature_valid;
}
// Checks for FAT32
if (strncmp((((void *)&bpb) + 0x52), "FAT", 3) == 0) {
goto valid;
goto signature_valid;
}
// Checks for FAT32 (with 64-bit sector count)
if (strncmp((((void *)&bpb) + 0x03), "FAT32", 5) == 0) {
goto valid;
goto signature_valid;
}
return 1;
valid:;
signature_valid:;
const uint8_t sector_per_cluster_valid_values[] = { 1, 2, 4, 8, 16, 32, 64, 128 };
for (size_t i = 0; i < SIZEOF_ARRAY(sector_per_cluster_valid_values); i++) {
if (bpb.sectors_per_cluster == sector_per_cluster_valid_values[i]) {
goto sector_per_cluster_valid;
}
}
return 1;
sector_per_cluster_valid:;
const uint16_t bytes_per_sector_valid_values[] = { 512, 1024, 2048, 4096 };
for (size_t i = 0; i < SIZEOF_ARRAY(bytes_per_sector_valid_values); i++) {
if (bpb.bytes_per_sector == bytes_per_sector_valid_values[i]) {
goto bytes_per_sector_valid;
}
}
return 1;
bytes_per_sector_valid:;
// The following mess to identify the FAT type is from the FAT spec
// at paragraph 3.5
size_t root_dir_sects = ((bpb.root_entries_count * 32) + (bpb.bytes_per_sector - 1)) / bpb.bytes_per_sector;