diff options
| -rw-r--r-- | sbin/fsck_msdosfs/fat.c | 36 |
1 files changed, 27 insertions, 9 deletions
diff --git a/sbin/fsck_msdosfs/fat.c b/sbin/fsck_msdosfs/fat.c index 55f9bbb..0b0bd9e 100644 --- a/sbin/fsck_msdosfs/fat.c +++ b/sbin/fsck_msdosfs/fat.c @@ -77,7 +77,7 @@ checkdirty(int fs, struct bootblock *boot) u_char *buffer; int ret = 0; - if (boot->ClustMask == CLUST12_MASK) + if (boot->ClustMask != CLUST16_MASK && boot->ClustMask != CLUST32_MASK) return 0; off = boot->ResSectors; @@ -99,14 +99,32 @@ checkdirty(int fs, struct bootblock *boot) goto err; } - if (buffer[0] == boot->Media && buffer[1] == 0xff && buffer[2] == 0xff - && ((boot->ClustMask == CLUST16_MASK && buffer[3] == 0x7f) - || (boot->ClustMask == CLUST32_MASK && buffer[3] == 0x0f - && buffer[4] == 0xff && buffer[5] == 0xff - && buffer[6] == 0xff && buffer[7] == 0x07))) - ret = 0; - else - ret = 1; + /* + * If we don't understand the FAT, then the file system must be + * assumed to be unclean. + */ + if (buffer[0] != boot->Media || buffer[1] != 0xff) + goto err; + if (boot->ClustMask == CLUST16_MASK) { + if ((buffer[2] & 0xf8) != 0xf8 || (buffer[3] & 0x3f) != 0x3f) + goto err; + } else { + if (buffer[2] != 0xff || (buffer[3] & 0x0f) != 0x0f + || (buffer[4] & 0xf8) != 0xf8 || buffer[5] != 0xff + || buffer[6] != 0xff || (buffer[7] & 0x03) != 0x03) + goto err; + } + + /* + * Now check the actual clean flag (and the no-error flag). + */ + if (boot->ClustMask == CLUST16_MASK) { + if ((buffer[3] & 0xc0) == 0xc0) + ret = 1; + } else { + if ((buffer[7] & 0x0c) == 0x0c) + ret = 1; + } err: free(buffer); |
