On Tue, Jan 16, 2018 at 09:34:32AM -0800, Darrick J. Wong wrote:

On Tue, Jan 16, 2018 at 07:48:46AM -0500, Brian Foster wrote:

quoted

On Mon, Jan 15, 2018 at 12:03:13PM -0800, Darrick J. Wong wrote:

quoted

From: Darrick J. Wong <redacted>

Currently, we don't check sb_agblocks or sb_agblklog when we validate
the superblock, which means that we can fuzz garbage values into those
values and the mount succeeds.  This leads to all sorts of UBSAN
warnings in xfs/350 since we can then coerce other parts of xfs into
shifting by ridiculously large values.

Signed-off-by: Darrick J. Wong <redacted>
---
v2: simplify ag min/max size definitions
---
 fs/xfs/libxfs/xfs_fs.h |    7 +++++++
 fs/xfs/libxfs/xfs_sb.c |    3 +++
 2 files changed, 10 insertions(+)

diff --git a/fs/xfs/libxfs/xfs_fs.h b/fs/xfs/libxfs/xfs_fs.h
index fc4386a..3ab1870 100644
--- a/fs/xfs/libxfs/xfs_fs.h
+++ b/fs/xfs/libxfs/xfs_fs.h

@@ -233,6 +233,13 @@ typedef struct xfs_fsop_resblks {
 #define XFS_MAX_LOG_BLOCKS	(1024 * 1024ULL)
 #define XFS_MIN_LOG_BYTES	(10 * 1024 * 1024ULL)
 
+/*
+ * Limits on sb_agblocks/sb_agblklog -- mkfs won't format AGs smaller than
+ * 16MB or larger than 1TB.
+ */
+#define XFS_AG_MIN_BYTES	(1ULL << 24)	/* 16 MB */
+#define XFS_AG_MAX_BYTES	(1ULL << 40)	/* 1 TB */
+

Dave's comment aside... just a nit: the definitions above use
XFS_[MIN|MAX]_* naming rather than XFS_AG_*. It would be nice to be
consistent there if we stick with these.

Since I was extracting the constants from xfs_multidisk.h I thought it
important to maintain the symbolic name to avoid breaking userspace.
I guess we /could/ just add XFS_MIN_AG_BYTES to libxfs and change
xfs_multidisk.h to do:

Oh, I missed that..

#define XFS_AG_MIN_BYTES	(XFS_MIN_AG_BYTES)

Or just decide that we don't care since we never install that header to
/usr/include ?

I think elevating these into libxfs warrant using whatever
sane/clean/consistent names fit in best from the perspective of libxfs.
If this is an internal define in xfsprogs, perhaps we can just
s/XFS_AG_MIN_BYTES/XFS_MIN_AG_BYTES/ there once this change trickles
down? Looks like it's only used in a handful of places.

Brian

--D

quoted

Brian

quoted

 /* keep the maximum size under 2^31 by a small amount */
 #define XFS_MAX_LOG_BYTES \
 	((2 * 1024 * 1024 * 1024ULL) - XFS_MIN_LOG_BYTES)

diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
index 08e44a0..bdb4f74 100644
--- a/fs/xfs/libxfs/xfs_sb.c
+++ b/fs/xfs/libxfs/xfs_sb.c

@@ -253,6 +253,9 @@ xfs_mount_validate_sb(
 	    sbp->sb_inodesize != (1 << sbp->sb_inodelog)		||
 	    sbp->sb_logsunit > XLOG_MAX_RECORD_BSIZE			||
 	    sbp->sb_inopblock != howmany(sbp->sb_blocksize,sbp->sb_inodesize) ||
+	    XFS_FSB_TO_B(mp, sbp->sb_agblocks) < XFS_AG_MIN_BYTES	||
+	    XFS_FSB_TO_B(mp, sbp->sb_agblocks) > XFS_AG_MAX_BYTES	||
+	    sbp->sb_agblklog != xfs_highbit32(sbp->sb_agblocks - 1) + 1	||
 	    (sbp->sb_blocklog - sbp->sb_inodelog != sbp->sb_inopblog)	||
 	    (sbp->sb_rextsize * sbp->sb_blocksize > XFS_MAX_RTEXTSIZE)	||
 	    (sbp->sb_rextsize * sbp->sb_blocksize < XFS_MIN_RTEXTSIZE)	||
--

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