[PATCH B] xfs: More robust inode extent count validation

[Tim Gardner]

From: Dave Chinner <dchinner at redhat.com>

When the inode is in extent format, it can't have more extents that
fit in the inode fork. We don't currenty check this, and so this
corruption goes unnoticed by the inode verifiers. This can lead to
crashes operating on invalid in-memory structures.

Attempts to access such a inode will now error out in the verifier
rather than allowing modification operations to proceed.

Reported-by: Wen Xu <wen.xu at gatech.edu>
Signed-off-by: Dave Chinner <dchinner at redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong at oracle.com>
[darrick: fix a typedef, add some braces and breaks to shut up compiler warnings]
Signed-off-by: Darrick J. Wong <darrick.wong at oracle.com>
(backported from commit 23fcb3340d033d9f081e21e6c12c2db7eaa541d3)
Signed-off-by: Tim Gardner <tim.gardner at canonical.com>

---
[ Conflicts:
	fs/xfs/libxfs/xfs_inode_buf.c
	Return false if xfs_dinode_verify_fork() is non-zero ]
	
 fs/xfs/libxfs/xfs_format.h    |  3 ++
 fs/xfs/libxfs/xfs_inode_buf.c | 73 ++++++++++++++++++++++-------------
 2 files changed, 49 insertions(+), 27 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
index 42956d8d95ed..3fe13c890289 100644
--- a/fs/xfs/libxfs/xfs_format.h
+++ b/fs/xfs/libxfs/xfs_format.h
@@ -971,6 +971,9 @@ typedef enum xfs_dinode_fmt {
 		XFS_DFORK_DSIZE(dip, mp) : \
 		XFS_DFORK_ASIZE(dip, mp))
 
+#define XFS_DFORK_MAXEXT(dip, mp, w) \
+	(XFS_DFORK_SIZE(dip, mp, w) / sizeof(struct xfs_bmbt_rec))
+
 /*
  * Return pointers to the data or attribute forks.
  */
diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
index 2ff83364e352..eb239cf52eb4 100644
--- a/fs/xfs/libxfs/xfs_inode_buf.c
+++ b/fs/xfs/libxfs/xfs_inode_buf.c
@@ -381,12 +381,54 @@ xfs_log_dinode_to_disk(
 	}
 }
 
+static xfs_failaddr_t
+xfs_dinode_verify_fork(
+	struct xfs_dinode	*dip,
+	struct xfs_mount	*mp,
+	int			whichfork)
+{
+	uint32_t		di_nextents = XFS_DFORK_NEXTENTS(dip, whichfork);
+
+	switch (XFS_DFORK_FORMAT(dip, whichfork)) {
+	case XFS_DINODE_FMT_LOCAL:
+		/*
+		 * no local regular files yet
+		 */
+		if (whichfork == XFS_DATA_FORK) {
+			if (S_ISREG(be16_to_cpu(dip->di_mode)))
+				return __this_address;
+			if (be64_to_cpu(dip->di_size) >
+					XFS_DFORK_SIZE(dip, mp, whichfork))
+				return __this_address;
+		}
+		if (di_nextents)
+			return __this_address;
+		break;
+	case XFS_DINODE_FMT_EXTENTS:
+		if (di_nextents > XFS_DFORK_MAXEXT(dip, mp, whichfork))
+			return __this_address;
+		break;
+	case XFS_DINODE_FMT_BTREE:
+		if (whichfork == XFS_ATTR_FORK) {
+			if (di_nextents > MAXAEXTNUM)
+				return __this_address;
+		} else if (di_nextents > MAXEXTNUM) {
+			return __this_address;
+		}
+		break;
+	default:
+		return __this_address;
+	}
+	return NULL;
+}
+
 bool
 xfs_dinode_verify(
 	struct xfs_mount	*mp,
 	xfs_ino_t		ino,
 	struct xfs_dinode	*dip)
 {
+	xfs_failaddr_t		fa;
 	uint16_t		mode;
 	uint16_t		flags;
 	uint64_t		flags2;
@@ -434,24 +476,9 @@ xfs_dinode_verify(
 	case S_IFREG:
 	case S_IFLNK:
 	case S_IFDIR:
-		switch (dip->di_format) {
-		case XFS_DINODE_FMT_LOCAL:
-			/*
-			 * no local regular files yet
-			 */
-			if (S_ISREG(mode))
-				return false;
-			if (di_size > XFS_DFORK_DSIZE(dip, mp))
-				return false;
-			if (dip->di_nextents)
-				return false;
-			/* fall through */
-		case XFS_DINODE_FMT_EXTENTS:
-		case XFS_DINODE_FMT_BTREE:
-			break;
-		default:
+		fa = xfs_dinode_verify_fork(dip, mp, XFS_DATA_FORK);
+		if (fa)
 			return false;
-		}
 		break;
 	case 0:
 		/* Uninitialized inode ok. */
@@ -461,17 +488,9 @@ xfs_dinode_verify(
 	}
 
 	if (XFS_DFORK_Q(dip)) {
-		switch (dip->di_aformat) {
-		case XFS_DINODE_FMT_LOCAL:
-			if (dip->di_anextents)
-				return false;
-		/* fall through */
-		case XFS_DINODE_FMT_EXTENTS:
-		case XFS_DINODE_FMT_BTREE:
-			break;
-		default:
+		fa = xfs_dinode_verify_fork(dip, mp, XFS_ATTR_FORK);
+		if (fa)
 			return false;
-		}
 	} else {
 		/*
 		 * If there is no fork offset, this may be a freshly-made inode
-- 
2.17.1