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Implement checking of .' and ..' entries of subdirectory.

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Reviewed by:		pfg
Obtained from:		Android b6ee08aadb%5E%21/
MFC after:		2 weeks
Differential Revision:	https://reviews.freebsd.org/D19824
This commit is contained in:
delphij 2019-04-05 02:21:16 +00:00
parent 03ec60d5bb
commit 437a93c1f4
1 changed files with 101 additions and 3 deletions
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104
sbin/fsck_msdosfs/dir.c
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@ -444,6 +444,77 @@ checksize(struct bootblock *boot, struct fatEntry *fat, u_char *p,
return FSOK;
}
static const u_char dot_name[] = {
'.', ' ',' ',' ',' ',' ',' ',' ',' ',' ',' ' };
static const u_char dotdot_name[] = {
'.', '.',' ',' ',' ',' ',' ',' ',' ',' ',' ' };
/*
* 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) != 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
@ -491,9 +562,6 @@ 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;
@ -830,6 +898,36 @@ 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 */