[PATCH] xfs_db: check for valid inode data pointer before dereferencing

[Dave Chinner <david@fromorbit.com>]

From: Dave Chinner <dchinner@redhat.com>

When processing an inode, the code checks various flags to determine
whether to output messages or not. When checking the CLI provided
inode numbers to be verbose about, we fail to check if the inode
data structre returned is valid or not before dereferencing it.
Hence running xfs_check with the "serious errors only" flag, xfs_db
will crash. Fix up the "should we output" logic to be safe.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
 db/check.c |   29 ++++++++++++++++-------------
 1 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/db/check.c b/db/check.c
index c62321b..4f8a62a 100644
--- a/db/check.c
+++ b/db/check.c
@@ -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 || (id && id->ilist) || CHECK_BLIST(bno))
 		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)
 			dbprintf(_("bad nextents %d for inode %lld, counted %d\n"),
 				idic.di_nextents, id->ino, nextents);
 		error++;
 	}
 	if (anextents != idic.di_anextents) {
-		if (!sflag || id->ilist || CHECK_BLIST(bno))
+		if (v)
 			dbprintf(_("bad anextents %d for inode %lld, counted "
 				 "%d\n"),
 				idic.di_anextents, id->ino, anextents);
-- 
1.7.1

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