Import revision 76844b29fc04ced003061bba03e7f6c947ed362c from FreeBSD.

Change-Id: I5d376e1121e10536530f66e6aae1df7d96ebfcaf

2 files changed, 128 insertions, 8 deletions

diff --git a/dir.c b/dir.c
index 38c7014..b990b0c 100644
--- a/dir.c
+++ b/dir.c
@@ -35,6 +35,8 @@ static const char rcsid[] =
   "$FreeBSD$";
 #endif /* not lint */
 
+#include <assert.h>
+#include <inttypes.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -329,8 +331,11 @@ delete(int f, struct bootblock *boot, struct fatEntry *fat, cl_t startcl,
 		}
 		off = startcl * boot->bpbSecPerClust + boot->ClusterOffset;
 		off *= boot->bpbBytesPerSec;
-		if (lseek(f, off, SEEK_SET) != off
-		    || read(f, delbuf, clsz) != clsz) {
+		if (lseek(f, off, SEEK_SET) != off) {
+			perr("Unable to lseek to %" PRId64, off);
+			return FSFATAL;
+		}
+		if (read(f, delbuf, clsz) != clsz) {
 			perr("Unable to read directory");
 			return FSFATAL;
 		}
@@ -338,8 +343,11 @@ delete(int f, struct bootblock *boot, struct fatEntry *fat, cl_t startcl,
 			*s = SLOT_DELETED;
 			s += 32;
 		}
-		if (lseek(f, off, SEEK_SET) != off
-		    || write(f, delbuf, clsz) != clsz) {
+		if (lseek(f, off, SEEK_SET) != off) {
+			perr("Unable to lseek to %" PRId64, off);
+			return FSFATAL;
+		}
+		if (write(f, delbuf, clsz) != clsz) {
 			perr("Unable to write directory");
 			return FSFATAL;
 		}
@@ -436,6 +444,75 @@ checksize(struct bootblock *boot, struct fatEntry *fat, u_char *p,
 	return FSOK;
 }
 
+static const u_char dot_name[11]    = ".          ";
+static const u_char dotdot_name[11] = "..         ";
+
+/*
+ * Basic sanity check if the subdirectory have good '.' and '..' entries,
+ * and they are directory entries.  Further sanity checks are performed
+ * when we traverse into it.
+ */
+static int
+check_subdirectory(int f, struct bootblock *boot, struct dosDirEntry *dir)
+{
+	u_char *buf, *cp;
+	off_t off;
+	cl_t cl;
+	int retval = FSOK;
+
+	cl = dir->head;
+	if (dir->parent && (cl < CLUST_FIRST || cl >= boot->NumClusters)) {
+		return FSERROR;
+	}
+
+	if (!(boot->flags & FAT32) && !dir->parent) {
+		off = boot->bpbResSectors + boot->bpbFATs *
+			boot->FATsecs;
+	} else {
+		off = cl * boot->bpbSecPerClust + boot->ClusterOffset;
+	}
+
+	/*
+	 * We only need to check the first two entries of the directory,
+	 * which is found in the first sector of the directory entry,
+	 * so read in only the first sector.
+	 */
+	buf = malloc(boot->bpbBytesPerSec);
+	if (buf == NULL) {
+		perr("No space for directory buffer (%u)",
+		    boot->bpbBytesPerSec);
+		return FSFATAL;
+	}
+
+	off *= boot->bpbBytesPerSec;
+	if (lseek(f, off, SEEK_SET) != off ||
+	    read(f, buf, boot->bpbBytesPerSec) != (ssize_t)boot->bpbBytesPerSec) {
+		perr("Unable to read directory");
+		free(buf);
+		return FSFATAL;
+	}
+
+	/*
+	 * Both `.' and `..' must be present and be the first two entries
+	 * and be ATTR_DIRECTORY of a valid subdirectory.
+	 */
+	cp = buf;
+	if (memcmp(cp, dot_name, sizeof(dot_name)) != 0 ||
+	    (cp[11] & ATTR_DIRECTORY) != ATTR_DIRECTORY) {
+		pwarn("%s: Incorrect `.' for %s.\n", __func__, dir->name);
+		retval |= FSERROR;
+	}
+	cp += 32;
+	if (memcmp(cp, dotdot_name, sizeof(dotdot_name)) != 0 ||
+	    (cp[11] & ATTR_DIRECTORY) != ATTR_DIRECTORY) {
+		pwarn("%s: Incorrect `..' for %s. \n", __func__, dir->name);
+		retval |= FSERROR;
+	}
+
+	free(buf);
+	return retval;
+}
+
 /*
  * Read a directory and
  *   - resolve long name records
@@ -483,9 +560,6 @@ readDosDirSection(int f, struct bootblock *boot, struct fatEntry *fat,
 			return FSFATAL;
 		}
 		last /= 32;
-		/*
-		 * Check `.' and `..' entries here?			XXX
-		 */
 		for (p = buffer, i = 0; i < last; i++, p += 32) {
 			if (dir->fsckflags & DIREMPWARN) {
 				*p = SLOT_EMPTY;
@@ -513,7 +587,8 @@ readDosDirSection(int f, struct bootblock *boot, struct fatEntry *fat,
 							   empcl, empty - buffer,
 							   cl, p - buffer, 1) == FSFATAL)
 							return FSFATAL;
-						q = empcl == cl ? empty : buffer;
+						q = ((empcl == cl) ? empty : buffer);
+						assert(q != NULL);
 						for (; q < p; q += 32)
 							*q = SLOT_DELETED;
 						mod |= THISMOD|FSDIRMOD;
@@ -821,6 +896,36 @@ readDosDirSection(int f, struct bootblock *boot, struct fatEntry *fat,
 						}
 					}
 					continue;
+				} else {
+					/*
+					 * Only one directory entry can point
+					 * to dir->head, it's '.'.
+					 */
+					if (dirent.head == dir->head) {
+						pwarn("%s entry in %s has incorrect start cluster\n",
+								dirent.name, fullpath(dir));
+						if (ask(1, "Remove")) {
+							*p = SLOT_DELETED;
+							mod |= THISMOD|FSDIRMOD;
+						} else
+							mod |= FSERROR;
+						continue;
+					} else if ((check_subdirectory(f, boot,
+					    &dirent) & FSERROR) == FSERROR) {
+						/*
+						 * A subdirectory should have
+						 * a dot (.) entry and a dot-dot
+						 * (..) entry of ATTR_DIRECTORY,
+						 * we will inspect further when
+						 * traversing into it.
+						 */
+						if (ask(1, "Remove")) {
+							*p = SLOT_DELETED;
+							mod |= THISMOD|FSDIRMOD;
+						} else
+							mod |= FSERROR;
+						continue;
+					}
 				}
 
 				/* create directory tree node */
@@ -964,6 +1069,7 @@ reconnect(int dosfs, struct bootblock *boot, struct fatEntry *fat, cl_t head)
 		if (lfcl < CLUST_FIRST || lfcl >= boot->NumClusters) {
 			/* Extend LOSTDIR?				XXX */
 			pwarn("No space in %s\n", LOSTDIR);
+			lfcl = (lostDir->head < boot->NumClusters) ? lostDir->head : 0;
 			return FSERROR;
 		}
 		lfoff = lfcl * boot->ClusterSize
diff --git a/fat.c b/fat.c
index 8a54837..7ea0274 100644
--- a/fat.c
+++ b/fat.c
@@ -705,6 +705,20 @@ checklost(int dosfs, struct bootblock *boot, struct fatEntry *fat)
 				ret = 1;
 			}
 		}
+		if (boot->FSNext != 0xffffffffU &&
+		    (boot->FSNext >= boot->NumClusters ||
+		    (boot->NumFree && fat[boot->FSNext].next != CLUST_FREE))) {
+			pwarn("Next free cluster in FSInfo block (%u) %s\n",
+			      boot->FSNext,
+			      (boot->FSNext >= boot->NumClusters) ? "invalid" : "not free");
+			if (ask(1, "fix"))
+				for (head = CLUST_FIRST; head < boot->NumClusters; head++)
+					if (fat[head].next == CLUST_FREE) {
+						boot->FSNext = head;
+						ret = 1;
+						break;
+					}
+		}
 		if (ret)
 			mod |= writefsinfo(dosfs, boot);
 	}