git: 6bae6625e0e0 - main - Improve handling of missing '.' and '..' in UFS directories.

The branch main has been updated by mckusick:

URL: https://cgit.FreeBSD.org/src/commit/?id=6bae6625e0e06816c80ac4971dfccf0643abe3f0

commit 6bae6625e0e06816c80ac4971dfccf0643abe3f0
Author:     Kirk McKusick <mckusick@FreeBSD.org>
AuthorDate: 2022-08-17 21:19:59 +0000
Commit:     Kirk McKusick <mckusick@FreeBSD.org>
CommitDate: 2022-08-17 21:19:59 +0000

    Improve handling of missing '.' and '..' in UFS directories.
    
    The UFS filesystem expects to find '.' and '..' as the first two entries
    in a directory. The kernel's UFS name cache can become quite confused
    when these two entries are not present as the first two entries.
    
    Prior to this change, when the fsck_ffs(8) utility detected that
    '.' and/or '..' were missing, it would report them, but only offered
    to replace them if the space at the beginning of the directory was
    available. Otherwise it was left to the system administrator to
    move the offending file(s) out of the way and then rerun fsck_ffs(8)
    to create the '.' and '..' entries.
    
    With this change, fsck_ffs(8) will always be able to create the '.'
    and/or '..' entries. It moves any files in the way elsewhere in the
    directory block. If there is no room in the directory block to which
    to move them, they are placed in the lost+found directory.
    
    Reported by:  Peter Holm
    Sponsored by: The FreeBSD Foundation
---
 sbin/fsck_ffs/pass2.c | 127 ++++++++++++++++++++++++++++++++------------------
 1 file changed, 82 insertions(+), 45 deletions(-)

diff --git a/sbin/fsck_ffs/pass2.c b/sbin/fsck_ffs/pass2.c
index 8632cf4878b1..78815493fba8 100644
--- a/sbin/fsck_ffs/pass2.c
+++ b/sbin/fsck_ffs/pass2.c
@@ -217,9 +217,9 @@ pass2(void)
 			continue;
 		if (inp->i_dotdot == 0) {
 			inp->i_dotdot = inp->i_parent;
-			fileerror(inp->i_parent, inp->i_number, "MISSING '..'");
-			if (reply("FIX") == 0)
-				continue;
+			if (debug)
+				fileerror(inp->i_parent, inp->i_number,
+				    "DEFERRED MISSING '..' FIX");
 			(void)makeentry(inp->i_number, inp->i_parent, "..");
 			inoinfo(inp->i_parent)->ino_linkcnt--;
 			continue;
@@ -289,7 +289,7 @@ pass2check(struct inodesc *idesc)
 	struct inode ip;
 	union dinode *dp;
 	const char *errmsg;
-	struct direct proto;
+	struct direct proto, *newdirp;
 
 	/*
 	 * check for "."
@@ -301,45 +301,52 @@ pass2check(struct inodesc *idesc)
 	if (dirp->d_ino != 0 && strcmp(dirp->d_name, ".") == 0) {
 		if (dirp->d_ino != idesc->id_number) {
 			direrror(idesc->id_number, "BAD INODE NUMBER FOR '.'");
-			dirp->d_ino = idesc->id_number;
-			if (reply("FIX") == 1)
+			if (reply("FIX") == 1) {
+				dirp->d_ino = idesc->id_number;
 				ret |= ALTERED;
+			}
 		}
 		if (dirp->d_type != DT_DIR) {
 			direrror(idesc->id_number, "BAD TYPE VALUE FOR '.'");
-			dirp->d_type = DT_DIR;
-			if (reply("FIX") == 1)
+			if (reply("FIX") == 1) {
+				dirp->d_type = DT_DIR;
 				ret |= ALTERED;
+			}
 		}
 		goto chk1;
 	}
-	direrror(idesc->id_number, "MISSING '.'");
 	proto.d_ino = idesc->id_number;
 	proto.d_type = DT_DIR;
 	proto.d_namlen = 1;
 	(void)strcpy(proto.d_name, ".");
 	entrysize = DIRSIZ(0, &proto);
-	if (dirp->d_ino != 0 && strcmp(dirp->d_name, "..") != 0) {
-		pfatal("CANNOT FIX, FIRST ENTRY IN DIRECTORY CONTAINS %s\n",
-			dirp->d_name);
-	} else if (dirp->d_reclen < entrysize) {
-		pfatal("CANNOT FIX, INSUFFICIENT SPACE TO ADD '.'\n");
-	} else if (dirp->d_reclen < 2 * entrysize) {
+	direrror(idesc->id_number, "MISSING '.'");
+	errmsg = "ADD '.' ENTRY";
+	if (dirp->d_reclen < entrysize + DIRSIZ(0, dirp)) {
+		/* Not enough space to add '.', replace first entry with '.' */
+		if (dirp->d_ino != 0) {
+			pwarn("\nFIRST ENTRY IN DIRECTORY CONTAINS %s\n",
+			     dirp->d_name);
+			errmsg = "REPLACE WITH '.'";
+		}
+		if (reply(errmsg) == 0)
+			goto chk1;
 		proto.d_reclen = dirp->d_reclen;
 		memmove(dirp, &proto, (size_t)entrysize);
-		if (reply("FIX") == 1)
-			ret |= ALTERED;
+		ret |= ALTERED;
 	} else {
-		n = dirp->d_reclen - entrysize;
+		/* Move over first entry and add '.' entry */
+		if (reply(errmsg) == 0)
+			goto chk1;
+		newdirp = (struct direct *)((char *)(dirp) + entrysize);
+		dirp->d_reclen -= entrysize;
+		memmove(newdirp, dirp, dirp->d_reclen);
 		proto.d_reclen = entrysize;
 		memmove(dirp, &proto, (size_t)entrysize);
 		idesc->id_entryno++;
-		inoinfo(dirp->d_ino)->ino_linkcnt--;
-		dirp = (struct direct *)((char *)(dirp) + entrysize);
-		memset(dirp, 0, (size_t)n);
-		dirp->d_reclen = n;
-		if (reply("FIX") == 1)
-			ret |= ALTERED;
+		inoinfo(idesc->id_number)->ino_linkcnt--;
+		dirp = newdirp;
+		ret |= ALTERED;
 	}
 chk1:
 	if (idesc->id_entryno > 1)
@@ -372,30 +379,60 @@ chk1:
 		}
 		goto chk2;
 	}
-	if (dirp->d_ino != 0 && strcmp(dirp->d_name, ".") != 0) {
-		fileerror(inp->i_parent, idesc->id_number, "MISSING '..'");
-		pfatal("CANNOT FIX, SECOND ENTRY IN DIRECTORY CONTAINS %s\n",
-			dirp->d_name);
-		inp->i_dotdot = (ino_t)-1;
-	} else if (dirp->d_reclen < entrysize) {
-		fileerror(inp->i_parent, idesc->id_number, "MISSING '..'");
-		pfatal("CANNOT FIX, INSUFFICIENT SPACE TO ADD '..'\n");
-		inp->i_dotdot = (ino_t)-1;
-	} else if (inp->i_parent != 0) {
-		/*
-		 * We know the parent, so fix now.
-		 */
-		inp->i_dotdot = inp->i_parent;
-		fileerror(inp->i_parent, idesc->id_number, "MISSING '..'");
+	fileerror(inp->i_parent != 0 ? inp->i_parent : idesc->id_number,
+	    idesc->id_number, "MISSING '..'");
+	errmsg = "ADD '..' ENTRY";
+	if (dirp->d_reclen < entrysize + DIRSIZ(0, dirp)) {
+		/* No space to add '..', replace second entry with '..' */
+		if (dirp->d_ino != 0) {
+			pfatal("SECOND ENTRY IN DIRECTORY CONTAINS %s\n",
+			    dirp->d_name);
+			errmsg = "REPLACE WITH '..'";
+		}
+		if (reply(errmsg) == 0) {
+			inp->i_dotdot = (ino_t)-1;
+			goto chk2;
+		}
+		if (proto.d_ino == 0) {
+			/* Defer processing until parent known */
+			idesc->id_entryno++;
+			if (debug)
+				printf("(FIX DEFERRED)\n");
+		}
+		inp->i_dotdot = proto.d_ino;
 		proto.d_reclen = dirp->d_reclen;
 		memmove(dirp, &proto, (size_t)entrysize);
-		if (reply("FIX") == 1)
-			ret |= ALTERED;
+		ret |= ALTERED;
+	} else {
+		/* Move over second entry and add '..' entry */
+		if (reply(errmsg) == 0) {
+			inp->i_dotdot = (ino_t)-1;
+			goto chk2;
+		}
+		if (proto.d_ino == 0) {
+			/* Defer processing until parent known */
+			idesc->id_entryno++;
+			if (debug)
+				printf("(FIX DEFERRED)\n");
+		}
+		inp->i_dotdot = proto.d_ino;
+		if (dirp->d_ino == 0) {
+			proto.d_reclen = dirp->d_reclen;
+			memmove(dirp, &proto, (size_t)entrysize);
+		} else {
+			newdirp = (struct direct *)((char *)(dirp) + entrysize);
+			dirp->d_reclen -= entrysize;
+			memmove(newdirp, dirp, dirp->d_reclen);
+			proto.d_reclen = entrysize;
+			memmove(dirp, &proto, (size_t)entrysize);
+			if (dirp->d_ino != 0) {
+				idesc->id_entryno++;
+				inoinfo(dirp->d_ino)->ino_linkcnt--;
+			}
+			dirp = newdirp;
+		}
+		ret |= ALTERED;
 	}
-	idesc->id_entryno++;
-	if (dirp->d_ino != 0)
-		inoinfo(dirp->d_ino)->ino_linkcnt--;
-	return (ret|KEEPON);
 chk2:
 	if (dirp->d_ino == 0)
 		return (ret|KEEPON);