segment fault when running xfs_check -s

Hi,

Recently I was playing with xfsprogs, and did some test on xfs_check tools in this mothod:
1.make a xfs fs on one partition.
mkfs.xfs -f /dev/sda2
2.randomly modify some blocks on this volume using xfs_db. xfs_db -x -c blockget -c "blocktrash -3 -s 36 -n 81" /dev/sda2 3.run xfs_check -s
xfs_check -s /dev/sda2

the output saying:
[root@test1 ~]# xfs_check -s /dev/sda2
bad version number 0x78 for inode 135
bad magic number 0xa855 for inode 154
bad magic number 0x5024 for inode 165
/usr/local/bin/xfs_check: line 28: 769 Segmentation fault xfs_db
$DBOPTS -F -i -p xfs_check -c "blockget$OPTS" $1

if I run xfs_check without -s option, don't have this fault.

Is this a known problem?

I tried the latest code ,also have this problem.

Quoted 19 lines · xiaowei hu

Hi,

Recently I was playing with xfsprogs, and did some test on xfs_check tools in this mothod:
1.make a xfs fs on one partition.
mkfs.xfs -f /dev/sda2
2.randomly modify some blocks on this volume using xfs_db. xfs_db -x -c blockget -c "blocktrash -3 -s 36 -n 81" /dev/sda2 3.run xfs_check -s
xfs_check -s /dev/sda2

the output saying:
[root@test1 ~]# xfs_check -s /dev/sda2
bad version number 0x78 for inode 135
bad magic number 0xa855 for inode 154
bad magic number 0x5024 for inode 165
/usr/local/bin/xfs_check: line 28: 769 Segmentation fault xfs_db
$DBOPTS -F -i -p xfs_check -c "blockget$OPTS" $1

Quoted 3 lines

if I run xfs_check without -s option, don't have this fault.

Is this a known problem?

No.

Quoted 1 line

I tried the latest code ,also have this problem.

Yeah, the code determining whether to output a message is broken:

2651 if (!isfree) {

2652                 id = find_inode(ino, 1);
2653                 bno = XFS_INO_TO_FSB(mp, ino);
2654                 blkmap = NULL;

2655 }

find_inode() checks a list created by the "-i <ino #>" command line option, so will always return NULL for this test case. Most of the checks do this:

2657 if (!sflag || isfree || id->ilist || CHECK_BLIST(bno))

sflag is set by the "-s" command line option, which is why this problem requires that to be set - the output checks don't get past this otherwise.

isfree is a parameter passed into to say whether the inode is allocated or not. The code hence assumes that if !isfree, then id != NULL, which is certainly not the case. Hence it can blow up if id = NULL.

The line it crashed on:

2670 if (isfree) {
2671 if (idic.di_nblocks != 0) {
2672 >>>>>> if (!sflag || id->ilist || CHECK_BLIST(bno))

Looks like a clear case of copy-n-paste error - if isfree is set, the id _must_ be null and we go kaboom.

It looks like none of the code in this function actually checks for whether id is valid or not after find_inode and dereferencing the reurn pointer.

The patch below should fix the problem.

Cheers,

Dave.

Signature · 6 lines

Dave Chinner
[email protected]

---
 db/check.c |   29 ++++++++++++++++-------------
 1 files changed, 16 insertions(+), 13 deletions(-)

db/check.c +15 -12

index 7620d9c..e0dcf63 100644
@@ -2619,6 +2619,7 @@ process_inode(
 	xfs_qcnt_t		ic = 0;
 	xfs_qcnt_t		rc = 0;
 	xfs_dqid_t		dqprid;
+	int			v = 0;
 	static char		okfmts[] = {
 		0,				/* type 0 unused */
 		1 << XFS_DINODE_FMT_DEV,	/* FIFO */

@@ -2653,15 +2654,16 @@ process_inode(
 		bno = XFS_INO_TO_FSB(mp, ino);
 		blkmap = NULL;
 	}
+	v = (!sflag || (id && id->ilist) || CHECK_BLIST(bno));
 	if (idic.di_magic != XFS_DINODE_MAGIC) {
-		if (!sflag || isfree || id->ilist || CHECK_BLIST(bno))
+		if (isfree || v)
 			dbprintf(_("bad magic number %#x for inode %lld\n"),
 				idic.di_magic, ino);
 		error++;
 		return;
 	}
 	if (!XFS_DINODE_GOOD_VERSION(idic.di_version)) {
-		if (!sflag || isfree || id->ilist || CHECK_BLIST(bno))
+		if (isfree || v)
 			dbprintf(_("bad version number %#x for inode %lld\n"),
 				idic.di_version, ino);
 		error++;

@@ -2669,7 +2671,7 @@ process_inode(
 	}
 	if (isfree) {
 		if (idic.di_nblocks != 0) {
-			if (!sflag || id->ilist || CHECK_BLIST(bno))
+			if (v)
 				dbprintf(_("bad nblocks %lld for free inode "
 					 "%lld\n"),
 					idic.di_nblocks, ino);

@@ -2680,21 +2682,22 @@ process_inode(
 		else
 			nlink = idic.di_nlink;
 		if (nlink != 0) {
-			if (!sflag || id->ilist || CHECK_BLIST(bno))
+			if (v)
 				dbprintf(_("bad nlink %d for free inode %lld\n"),
 					nlink, ino);
 			error++;
 		}
 		if (idic.di_mode != 0) {
-			if (!sflag || id->ilist || CHECK_BLIST(bno))
+			if (v)
 				dbprintf(_("bad mode %#o for free inode %lld\n"),
 					idic.di_mode, ino);
 			error++;
 		}
 		return;
 	}
+
 	if (be32_to_cpu(dip->di_next_unlinked) != NULLAGINO) {
-		if (!sflag || isfree || id->ilist || CHECK_BLIST(bno))
+		if (v)
 			dbprintf(_("bad next unlinked %#x for inode %lld\n"),
 				be32_to_cpu(dip->di_next_unlinked), ino);
 		error++;

@@ -2704,27 +2707,27 @@ process_inode(
 	 */
 	if ((((idic.di_mode & S_IFMT) >> 12) > 15) ||
 	    (!(okfmts[(idic.di_mode & S_IFMT) >> 12] & (1 << idic.di_format)))) {
-		if (!sflag || id->ilist || CHECK_BLIST(bno))
+		if (v)
 			dbprintf(_("bad format %d for inode %lld type %#o\n"),
 				idic.di_format, id->ino, idic.di_mode & S_IFMT);
 		error++;
 		return;
 	}
 	if ((unsigned int)XFS_DFORK_ASIZE(dip, mp) >= XFS_LITINO(mp))  {
-		if (!sflag || id->ilist)
+		if (v)
 			dbprintf(_("bad fork offset %d for inode %lld\n"),
 				idic.di_forkoff, id->ino);
 		error++;
 		return;
 	}
 	if ((unsigned int)idic.di_aformat > XFS_DINODE_FMT_BTREE)  {
-		if (!sflag || id->ilist)
+		if (v)
 			dbprintf(_("bad attribute format %d for inode %lld\n"),
 				idic.di_aformat, id->ino);
 		error++;
 		return;
 	}
-	if (verbose || id->ilist || CHECK_BLIST(bno))
+	if (verbose || v)
 		dbprintf(_("inode %lld mode %#o fmt %s "
 			 "afmt %s "
 			 "nex %d anex %d nblk %lld sz %lld%s%s%s%s%s%s%s\n"),

@@ -2844,20 +2847,20 @@ process_inode(
 	}
 	totblocks = totdblocks + totiblocks + atotdblocks + atotiblocks;
 	if (totblocks != idic.di_nblocks) {
-		if (!sflag || id->ilist || CHECK_BLIST(bno))
+		if (v)
 			dbprintf(_("bad nblocks %lld for inode %lld, counted "
 				 "%lld\n"),
 				idic.di_nblocks, id->ino, totblocks);
 		error++;
 	}
 	if (nextents != idic.di_nextents) {
-		if (!sflag || id->ilist || CHECK_BLIST(bno))
+		if (v)