d/freebsd-skq
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

When compacting directories, ufs_direnter() always trusted DIRSIZ()

Browse Source 
to supply the number of bytes to be bcopy()'d to move an entry. If
d_ino == 0 however, DIRSIZ() is not guaranteed to return a sensible
length, so ufs_direnter could end up corrupting a directory during
compaction. In practice I believe this can only happen after fsck_ffs
has fixed a previously-corrupted directory.

We now deal with any mid-block unused entries specially to avoid
using DIRSIZ() or bcopy() on such entries. We also ensure that the
variables 'dsize' and 'spacefree' contain meaningful values at all
times. Add a few comments to describe better this intricate piece
of code.

The special handling of mid-block unused entries makes the dirhash-
specific bugfix in the previous revision (1.53) now uncecessary,
so this change removes it.

Reviewed by:	mckusick
This commit is contained in:
iedowse 2001-08-26 01:25:12 +00:00
parent 8638e55f32
commit c8ef91ce6c
1 changed files with 29 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

40
sys/ufs/ufs/ufs_lookup.c
View File

@ -869,26 +869,39 @@ ufs_direnter(dvp, tvp, dirp, cnp, newdirbp)
* dp->i_offset + dp->i_count would yield the space.
*/
ep = (struct direct *)dirbuf;
dsize = DIRSIZ(OFSFMT(dvp), ep);
dsize = ep->d_ino ? DIRSIZ(OFSFMT(dvp), ep) : 0;
spacefree = ep->d_reclen - dsize;
for (loc = ep->d_reclen; loc < dp->i_count; ) {
nep = (struct direct *)(dirbuf + loc);
if (ep->d_ino) {
/* trim the existing slot */
ep->d_reclen = dsize;
ep = (struct direct *)((char *)ep + dsize);
} else {
/* overwrite; nothing there; header is ours */
spacefree += dsize;
/* Trim the existing slot (NB: dsize may be zero). */
ep->d_reclen = dsize;
ep = (struct direct *)((char *)ep + dsize);
/* Read nep->d_reclen now as the bcopy() may clobber it. */
loc += nep->d_reclen;
if (nep->d_ino == 0) {
/*
* A mid-block unused entry. Such entries are
* never created by the kernel, but fsck_ffs
* can create them (and it doesn't fix them).
*
* Add up the free space, and initialise the
* relocated entry since we don't bcopy it.
*/
spacefree += nep->d_reclen;
ep->d_ino = 0;
dsize = 0;
continue;
}
dsize = DIRSIZ(OFSFMT(dvp), nep);
spacefree += nep->d_reclen - dsize;
#ifdef UFS_DIRHASH
if (dp->i_dirhash != NULL && nep->d_ino)
ufsdirhash_move(dp, nep, dp->i_offset + loc,
if (dp->i_dirhash != NULL)
ufsdirhash_move(dp, nep,
dp->i_offset + ((char *)nep - dirbuf),
dp->i_offset + ((char *)ep - dirbuf));
#endif
loc += nep->d_reclen;
if (DOINGSOFTDEP(dvp))
softdep_change_directoryentry_offset(dp, dirbuf,
(caddr_t)nep, (caddr_t)ep, dsize);
@ -896,6 +909,11 @@ ufs_direnter(dvp, tvp, dirp, cnp, newdirbp)
bcopy((caddr_t)nep, (caddr_t)ep, dsize);
}
/*
* Here, `ep' points to a directory entry containing `dsize' in-use
* bytes followed by `spacefree' unused bytes. If ep->d_ino == 0,
* then the entry is completely unused (dsize == 0). The value
* of ep->d_reclen is always indeterminate.
*
* Update the pointer fields in the previous entry (if any),
* copy in the new entry, and write out the block.
*/