From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
While running generic/103, I observed what looks like memory corruption
and (with slub debugging turned on) a slub redzone warning on i386 when
inactivating an inode with a 64k remote attr value.
On a v5 filesystem, maximally sized remote attr values require one block
more than 64k worth of space to hold both the remote attribute value
header (64 bytes). On a 4k block filesystem this results in a 68k
buffer; on a 64k block filesystem, this would be a 128k buffer. Note
that even though we'll never use more than 65,600 bytes of this buffer,
XFS_MAX_BLOCKSIZE is 64k.
This is a problem because the definition of struct xfs_buf_log_format
allows for XFS_MAX_BLOCKSIZE worth of dirty bitmap (64k). On i386 when we
invalidate a remote attribute, xfs_trans_binval zeroes all 68k worth of
the dirty map, writing right off the end of the log item and corrupting
memory. We've gotten away with this on x86_64 for years because the
compiler inserts a u32 padding on the end of struct xfs_buf_log_format.
Fortunately for us, remote attribute values are written to disk with
xfs_bwrite(), which is to say that they are not logged. Fix the problem
by removing all places where we could end up creating a buffer log item
for a remote attribute value and leave a note explaining why.
Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
---
fs/xfs/libxfs/xfs_attr_remote.c | 21 +++++++++++++++++++--
fs/xfs/xfs_attr_inactive.c | 34 ++++++----------------------------
2 files changed, 25 insertions(+), 30 deletions(-)
diff --git a/fs/xfs/libxfs/xfs_attr_remote.c b/fs/xfs/libxfs/xfs_attr_remote.c
index 6babdaac6057..1765f5351f9e 100644
--- a/fs/xfs/libxfs/xfs_attr_remote.c
+++ b/fs/xfs/libxfs/xfs_attr_remote.c
@@ -25,6 +25,23 @@
#define ATTR_RMTVALUE_MAPSIZE 1 /* # of map entries at once */
+/*
+ * Remote Attribute Values
+ * =======================
+ *
+ * Remote extended attribute values are conceptually simple -- they're written
+ * to data blocks mapped by an inode's attribute fork, and they have an upper
+ * size limit of 64k. Setting a value does not involve the XFS log.
+ *
+ * However, on a v5 filesystem, maximally sized remote attr values require one
+ * block more than 64k worth of space to hold both the remote attribute value
+ * header (64 bytes). On a 4k block filesystem this results in a 68k buffer;
+ * on a 64k block filesystem, this would be a 128k buffer. Note that the log
+ * format can only handle a dirty buffer of XFS_MAX_BLOCKSIZE length (64k).
+ * Therefore, we /must/ ensure that remote attribute value buffers never touch
+ * the logging system and therefore never have a log item.
+ */
+
/*
* Each contiguous block has a header, so it is not just a simple attribute
* length to FSB conversion.
@@ -401,7 +418,7 @@ xfs_attr_rmtval_get(
(map[i].br_startblock != HOLESTARTBLOCK));
dblkno = XFS_FSB_TO_DADDR(mp, map[i].br_startblock);
dblkcnt = XFS_FSB_TO_BB(mp, map[i].br_blockcount);
- error = xfs_trans_read_buf(mp, args->trans,
+ error = xfs_trans_read_buf(mp, NULL,
mp->m_ddev_targp,
dblkno, dblkcnt, 0, &bp,
&xfs_attr3_rmt_buf_ops);
@@ -411,7 +428,7 @@ xfs_attr_rmtval_get(
error = xfs_attr_rmtval_copyout(mp, bp, args->dp->i_ino,
&offset, &valuelen,
&dst);
- xfs_trans_brelse(args->trans, bp);
+ xfs_buf_relse(bp);
if (error)
return error;
diff --git a/fs/xfs/xfs_attr_inactive.c b/fs/xfs/xfs_attr_inactive.c
index 5ff49523d8ea..5c83dd3611af 100644
--- a/fs/xfs/xfs_attr_inactive.c
+++ b/fs/xfs/xfs_attr_inactive.c
@@ -30,17 +30,13 @@
*/
STATIC int
xfs_attr3_leaf_freextent(
- struct xfs_trans **trans,
struct xfs_inode *dp,
xfs_dablk_t blkno,
int blkcnt)
{
struct xfs_bmbt_irec map;
- struct xfs_buf *bp;
xfs_dablk_t tblkno;
- xfs_daddr_t dblkno;
int tblkcnt;
- int dblkcnt;
int nmap;
int error;
@@ -64,28 +60,12 @@ xfs_attr3_leaf_freextent(
ASSERT(map.br_startblock != DELAYSTARTBLOCK);
/*
- * If it's a hole, these are already unmapped
- * so there's nothing to invalidate.
+ * Mark any incore buffers for the remote value as stale. We
+ * never log remote attr value buffers, so the buffer should be
+ * easy to kill.
*/
- if (map.br_startblock != HOLESTARTBLOCK) {
-
- dblkno = XFS_FSB_TO_DADDR(dp->i_mount,
- map.br_startblock);
- dblkcnt = XFS_FSB_TO_BB(dp->i_mount,
- map.br_blockcount);
- bp = xfs_trans_get_buf(*trans,
- dp->i_mount->m_ddev_targp,
- dblkno, dblkcnt, 0);
- if (!bp)
- return -ENOMEM;
- xfs_trans_binval(*trans, bp);
- /*
- * Roll to next transaction.
- */
- error = xfs_trans_roll_inode(trans, dp);
- if (error)
- return error;
- }
+ if (map.br_startblock != HOLESTARTBLOCK)
+ xfs_attr_rmtval_stale(dp, &map);
tblkno += map.br_blockcount;
tblkcnt -= map.br_blockcount;
@@ -174,9 +154,7 @@ xfs_attr3_leaf_inactive(
*/
error = 0;
for (lp = list, i = 0; i < count; i++, lp++) {
- tmp = xfs_attr3_leaf_freextent(trans, dp,
- lp->valueblk, lp->valuelen);
-
+ tmp = xfs_attr3_leaf_freextent(dp, lp->valueblk, lp->valuelen);
if (error == 0)
error = tmp; /* save only the 1st errno */
}
