generic/388 can cause the following "use after free" error to occur,
=============================================================================
BUG xfs_efi_item (Not tainted): Poison overwritten
-----------------------------------------------------------------------------
Disabling lock debugging due to kernel taint
INFO: 0x00000000292c4bd4-0x00000000292c4bd4. First byte 0x6a instead of 0x6b
INFO: Allocated in .kmem_zone_alloc+0xcc/0x190 age=79 cpu=0 pid=12436
.__slab_alloc+0x54/0x80
.kmem_cache_alloc+0x124/0x350
.kmem_zone_alloc+0xcc/0x190
.xfs_efi_init+0x48/0xf0
.xfs_extent_free_create_intent+0x40/0x130
.xfs_defer_intake_work+0x74/0x1e0
.xfs_defer_finish+0xac/0x5c0
.xfs_itruncate_extents+0x170/0x590
.xfs_inactive_truncate+0xcc/0x170
.xfs_inactive+0x1d8/0x2f0
.xfs_fs_destroy_inode+0xe4/0x3d0
.destroy_inode+0x68/0xb0
.do_unlinkat+0x1e8/0x390
system_call+0x58/0x6c
INFO: Freed in .xfs_efi_item_free+0x44/0x80 age=79 cpu=0 pid=12436
.kmem_cache_free+0x120/0x2b0
.xfs_efi_item_free+0x44/0x80
.xfs_trans_free_items+0xd4/0x130
.__xfs_trans_commit+0xd0/0x350
.xfs_trans_roll+0x4c/0x90
.xfs_defer_trans_roll+0xa4/0x2b0
.xfs_defer_finish+0xb8/0x5c0
.xfs_itruncate_extents+0x170/0x590
.xfs_inactive_truncate+0xcc/0x170
.xfs_inactive+0x1d8/0x2f0
.xfs_fs_destroy_inode+0xe4/0x3d0
.destroy_inode+0x68/0xb0
.do_unlinkat+0x1e8/0x390
system_call+0x58/0x6c
This happens due to the following interaction,
1. xfs_defer_finish() creates "extent free" intent item and adds it to the
per-transction list of log items.
2. xfs_defer_trans_roll() invokes __xfs_trans_commit(). Here, if the
XFS_MOUNT_FS_SHUTDOWN flag is set, we invoke io_unlock() operation
for each of the log items in the per-transction list. For "extent
free" log items xfs_efi_item_unlock() gets invoked which then frees
the xfs_efi_log_item.
3. xfs_defer_trans_roll() then invokes xfs_defer_trans_abort(). Since the
xfs_defer_pending->dfp_intent is still set to the "extent free" intent
item, we invoke xfs_extent_free_abort_intent(). This accesses the
previously freed xfs_efi_log_item to decrement the ref count.
This commit fixes the bug by invoking xfs_defer_trans_abort() only when
the log items in the per-transaction list have been committed to the
CIL. The log item "committed" status is being tracked by
xfs_defer_ops->dop_committed. This was the behaviour prior to commit
3ab78df2a59a485f479d26852a060acfd8c4ecd7 (xfs: rework xfs_bmap_free
callers to use xfs_defer_ops).
Reported-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Chandan Rajendra <chandan@xxxxxxxxxxxxxxxxxx>
---
fs/xfs/libxfs/xfs_defer.c | 6 +++---
fs/xfs/xfs_bmap_util.c | 2 +-
fs/xfs/xfs_inode.c | 2 +-
fs/xfs/xfs_trans.c | 8 +++++++-
fs/xfs/xfs_trans.h | 2 +-
fs/xfs/xfs_trans_inode.c | 2 +-
6 files changed, 14 insertions(+), 8 deletions(-)
diff --git a/fs/xfs/libxfs/xfs_defer.c b/fs/xfs/libxfs/xfs_defer.c
index 087fea0..eb879a0 100644
--- a/fs/xfs/libxfs/xfs_defer.c
+++ b/fs/xfs/libxfs/xfs_defer.c
@@ -256,13 +256,13 @@ xfs_defer_trans_roll(
trace_xfs_defer_trans_roll((*tp)->t_mountp, dop);
/* Roll the transaction. */
- error = xfs_trans_roll(tp);
+ error = xfs_trans_roll(tp, &dop->dop_committed);
if (error) {
trace_xfs_defer_trans_roll_error((*tp)->t_mountp, dop, error);
- xfs_defer_trans_abort(*tp, dop, error);
+ if (dop->dop_committed == true)
+ xfs_defer_trans_abort(*tp, dop, error);
return error;
}
- dop->dop_committed = true;
/* Rejoin the joined inodes. */
for (i = 0; i < XFS_DEFER_OPS_NR_INODES && dop->dop_inodes[i]; i++)
diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index c83f549..9d84d36 100644
--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -1830,7 +1830,7 @@ xfs_swap_change_owner(
if (error != -EAGAIN)
break;
- error = xfs_trans_roll(tpp);
+ error = xfs_trans_roll(tpp, NULL);
if (error)
break;
tp = *tpp;
diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 604ee38..6419549 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -1049,7 +1049,7 @@ xfs_dir_ialloc(
tp->t_flags &= ~(XFS_TRANS_DQ_DIRTY);
}
- code = xfs_trans_roll(&tp);
+ code = xfs_trans_roll(&tp, NULL);
if (committed != NULL)
*committed = 1;
diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
index 86f92df..1bf2505 100644
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -1057,12 +1057,15 @@ xfs_trans_cancel(
*/
int
xfs_trans_roll(
- struct xfs_trans **tpp)
+ struct xfs_trans **tpp,
+ bool *committed)
{
struct xfs_trans *trans = *tpp;
struct xfs_trans_res tres;
int error;
+ if (committed)
+ *committed = false;
/*
* Copy the critical parameters from one trans to the next.
*/
@@ -1082,6 +1085,9 @@ xfs_trans_roll(
if (error)
return error;
+ if (committed)
+ *committed = true;
+
/*
* Reserve space in the log for the next transaction.
* This also pushes items in the "AIL", the list of logged items,
diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h
index 9d542df..d4deb49 100644
--- a/fs/xfs/xfs_trans.h
+++ b/fs/xfs/xfs_trans.h
@@ -230,7 +230,7 @@ int xfs_trans_free_extent(struct xfs_trans *,
struct xfs_efd_log_item *, xfs_fsblock_t,
xfs_extlen_t, struct xfs_owner_info *);
int xfs_trans_commit(struct xfs_trans *);
-int xfs_trans_roll(struct xfs_trans **);
+int xfs_trans_roll(struct xfs_trans **, bool *);
int xfs_trans_roll_inode(struct xfs_trans **, struct xfs_inode *);
void xfs_trans_cancel(xfs_trans_t *);
int xfs_trans_ail_init(struct xfs_mount *);
diff --git a/fs/xfs/xfs_trans_inode.c b/fs/xfs/xfs_trans_inode.c
index 4a89da4..bedd5fd 100644
--- a/fs/xfs/xfs_trans_inode.c
+++ b/fs/xfs/xfs_trans_inode.c
@@ -147,7 +147,7 @@ xfs_trans_roll_inode(
int error;
xfs_trans_log_inode(*tpp, ip, XFS_ILOG_CORE);
- error = xfs_trans_roll(tpp);
+ error = xfs_trans_roll(tpp, NULL);
if (!error)
xfs_trans_ijoin(*tpp, ip, 0);
return error;
--
2.9.5
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