From: Dave Chinner dchinner@redhat.com
commit c7f87f3984cfa1e6d32806a715f35c5947ad9c09 upstream.
xlog_wait() on the CIL context can reference a freed context if the waiter doesn't get scheduled before the CIL context is freed. This can happen when a task is on the hard throttle and the CIL push aborts due to a shutdown. This was detected by generic/019:
thread 1 thread 2
__xfs_trans_commit xfs_log_commit_cil <CIL size over hard throttle limit> xlog_wait schedule xlog_cil_push_work wake_up_all <shutdown aborts commit> xlog_cil_committed kmem_free
remove_wait_queue spin_lock_irqsave --> UAF
Fix it by moving the wait queue to the CIL rather than keeping it in in the CIL context that gets freed on push completion. Because the wait queue is now independent of the CIL context and we might have multiple contexts in flight at once, only wake the waiters on the push throttle when the context we are pushing is over the hard throttle size threshold.
Fixes: 0e7ab7efe7745 ("xfs: Throttle commits on delayed background CIL push") Reported-by: Yu Kuai yukuai3@huawei.com Signed-off-by: Dave Chinner dchinner@redhat.com Reviewed-by: Darrick J. Wong darrick.wong@oracle.com Signed-off-by: Darrick J. Wong darrick.wong@oracle.com Reviewed-by: Christoph Hellwig hch@lst.de Acked-by: Darrick J. Wong djwong@kernel.org Signed-off-by: Chandan Babu R chandan.babu@oracle.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/xfs/xfs_log_cil.c | 10 +++++----- fs/xfs/xfs_log_priv.h | 2 +- 2 files changed, 6 insertions(+), 6 deletions(-)
--- a/fs/xfs/xfs_log_cil.c +++ b/fs/xfs/xfs_log_cil.c @@ -673,7 +673,8 @@ xlog_cil_push( /* * Wake up any background push waiters now this context is being pushed. */ - wake_up_all(&ctx->push_wait); + if (ctx->space_used >= XLOG_CIL_BLOCKING_SPACE_LIMIT(log)) + wake_up_all(&cil->xc_push_wait);
/* * Check if we've anything to push. If there is nothing, then we don't @@ -745,13 +746,12 @@ xlog_cil_push(
/* * initialise the new context and attach it to the CIL. Then attach - * the current context to the CIL committing lsit so it can be found + * the current context to the CIL committing list so it can be found * during log forces to extract the commit lsn of the sequence that * needs to be forced. */ INIT_LIST_HEAD(&new_ctx->committing); INIT_LIST_HEAD(&new_ctx->busy_extents); - init_waitqueue_head(&new_ctx->push_wait); new_ctx->sequence = ctx->sequence + 1; new_ctx->cil = cil; cil->xc_ctx = new_ctx; @@ -946,7 +946,7 @@ xlog_cil_push_background( if (cil->xc_ctx->space_used >= XLOG_CIL_BLOCKING_SPACE_LIMIT(log)) { trace_xfs_log_cil_wait(log, cil->xc_ctx->ticket); ASSERT(cil->xc_ctx->space_used < log->l_logsize); - xlog_wait(&cil->xc_ctx->push_wait, &cil->xc_push_lock); + xlog_wait(&cil->xc_push_wait, &cil->xc_push_lock); return; }
@@ -1222,12 +1222,12 @@ xlog_cil_init( INIT_LIST_HEAD(&cil->xc_committing); spin_lock_init(&cil->xc_cil_lock); spin_lock_init(&cil->xc_push_lock); + init_waitqueue_head(&cil->xc_push_wait); init_rwsem(&cil->xc_ctx_lock); init_waitqueue_head(&cil->xc_commit_wait);
INIT_LIST_HEAD(&ctx->committing); INIT_LIST_HEAD(&ctx->busy_extents); - init_waitqueue_head(&ctx->push_wait); ctx->sequence = 1; ctx->cil = cil; cil->xc_ctx = ctx; --- a/fs/xfs/xfs_log_priv.h +++ b/fs/xfs/xfs_log_priv.h @@ -247,7 +247,6 @@ struct xfs_cil_ctx { struct xfs_log_vec *lv_chain; /* logvecs being pushed */ struct list_head iclog_entry; struct list_head committing; /* ctx committing list */ - wait_queue_head_t push_wait; /* background push throttle */ struct work_struct discard_endio_work; };
@@ -281,6 +280,7 @@ struct xfs_cil { wait_queue_head_t xc_commit_wait; xfs_lsn_t xc_current_sequence; struct work_struct xc_push_work; + wait_queue_head_t xc_push_wait; /* background push throttle */ } ____cacheline_aligned_in_smp;
/*