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Message-Id: <20190708150525.110658846@linuxfoundation.org>
Date: Mon, 8 Jul 2019 17:13:18 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Eric Biggers <ebiggers@...gle.com>,
syzbot+fab6de82892b6b9c6191@...kaller.appspotmail.com,
syzbot+53c0b767f7ca0dc0c451@...kaller.appspotmail.com,
syzbot+a3accb352f9c22041cfa@...kaller.appspotmail.com,
Andrew Morton <akpm@...ux-foundation.org>,
Christoph Hellwig <hch@....de>,
Andrea Arcangeli <aarcange@...hat.com>,
Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 4.19 51/90] fs/userfaultfd.c: disable irqs for fault_pending and event locks
From: Eric Biggers <ebiggers@...gle.com>
commit cbcfa130a911c613a1d9d921af2eea171c414172 upstream.
When IOCB_CMD_POLL is used on a userfaultfd, aio_poll() disables IRQs
and takes kioctx::ctx_lock, then userfaultfd_ctx::fd_wqh.lock.
This may have to wait for userfaultfd_ctx::fd_wqh.lock to be released by
userfaultfd_ctx_read(), which in turn can be waiting for
userfaultfd_ctx::fault_pending_wqh.lock or
userfaultfd_ctx::event_wqh.lock.
But elsewhere the fault_pending_wqh and event_wqh locks are taken with
IRQs enabled. Since the IRQ handler may take kioctx::ctx_lock, lockdep
reports that a deadlock is possible.
Fix it by always disabling IRQs when taking the fault_pending_wqh and
event_wqh locks.
Commit ae62c16e105a ("userfaultfd: disable irqs when taking the
waitqueue lock") didn't fix this because it only accounted for the
fd_wqh lock, not the other locks nested inside it.
Link: http://lkml.kernel.org/r/20190627075004.21259-1-ebiggers@kernel.org
Fixes: bfe4037e722e ("aio: implement IOCB_CMD_POLL")
Signed-off-by: Eric Biggers <ebiggers@...gle.com>
Reported-by: syzbot+fab6de82892b6b9c6191@...kaller.appspotmail.com
Reported-by: syzbot+53c0b767f7ca0dc0c451@...kaller.appspotmail.com
Reported-by: syzbot+a3accb352f9c22041cfa@...kaller.appspotmail.com
Reviewed-by: Andrew Morton <akpm@...ux-foundation.org>
Cc: Christoph Hellwig <hch@....de>
Cc: Andrea Arcangeli <aarcange@...hat.com>
Cc: <stable@...r.kernel.org> [4.19+]
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
fs/userfaultfd.c | 42 ++++++++++++++++++++++++++----------------
1 file changed, 26 insertions(+), 16 deletions(-)
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -40,6 +40,16 @@ enum userfaultfd_state {
/*
* Start with fault_pending_wqh and fault_wqh so they're more likely
* to be in the same cacheline.
+ *
+ * Locking order:
+ * fd_wqh.lock
+ * fault_pending_wqh.lock
+ * fault_wqh.lock
+ * event_wqh.lock
+ *
+ * To avoid deadlocks, IRQs must be disabled when taking any of the above locks,
+ * since fd_wqh.lock is taken by aio_poll() while it's holding a lock that's
+ * also taken in IRQ context.
*/
struct userfaultfd_ctx {
/* waitqueue head for the pending (i.e. not read) userfaults */
@@ -459,7 +469,7 @@ vm_fault_t handle_userfault(struct vm_fa
blocking_state = return_to_userland ? TASK_INTERRUPTIBLE :
TASK_KILLABLE;
- spin_lock(&ctx->fault_pending_wqh.lock);
+ spin_lock_irq(&ctx->fault_pending_wqh.lock);
/*
* After the __add_wait_queue the uwq is visible to userland
* through poll/read().
@@ -471,7 +481,7 @@ vm_fault_t handle_userfault(struct vm_fa
* __add_wait_queue.
*/
set_current_state(blocking_state);
- spin_unlock(&ctx->fault_pending_wqh.lock);
+ spin_unlock_irq(&ctx->fault_pending_wqh.lock);
if (!is_vm_hugetlb_page(vmf->vma))
must_wait = userfaultfd_must_wait(ctx, vmf->address, vmf->flags,
@@ -553,13 +563,13 @@ vm_fault_t handle_userfault(struct vm_fa
* kernel stack can be released after the list_del_init.
*/
if (!list_empty_careful(&uwq.wq.entry)) {
- spin_lock(&ctx->fault_pending_wqh.lock);
+ spin_lock_irq(&ctx->fault_pending_wqh.lock);
/*
* No need of list_del_init(), the uwq on the stack
* will be freed shortly anyway.
*/
list_del(&uwq.wq.entry);
- spin_unlock(&ctx->fault_pending_wqh.lock);
+ spin_unlock_irq(&ctx->fault_pending_wqh.lock);
}
/*
@@ -584,7 +594,7 @@ static void userfaultfd_event_wait_compl
init_waitqueue_entry(&ewq->wq, current);
release_new_ctx = NULL;
- spin_lock(&ctx->event_wqh.lock);
+ spin_lock_irq(&ctx->event_wqh.lock);
/*
* After the __add_wait_queue the uwq is visible to userland
* through poll/read().
@@ -614,15 +624,15 @@ static void userfaultfd_event_wait_compl
break;
}
- spin_unlock(&ctx->event_wqh.lock);
+ spin_unlock_irq(&ctx->event_wqh.lock);
wake_up_poll(&ctx->fd_wqh, EPOLLIN);
schedule();
- spin_lock(&ctx->event_wqh.lock);
+ spin_lock_irq(&ctx->event_wqh.lock);
}
__set_current_state(TASK_RUNNING);
- spin_unlock(&ctx->event_wqh.lock);
+ spin_unlock_irq(&ctx->event_wqh.lock);
if (release_new_ctx) {
struct vm_area_struct *vma;
@@ -919,10 +929,10 @@ wakeup:
* the last page faults that may have been already waiting on
* the fault_*wqh.
*/
- spin_lock(&ctx->fault_pending_wqh.lock);
+ spin_lock_irq(&ctx->fault_pending_wqh.lock);
__wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, &range);
__wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, &range);
- spin_unlock(&ctx->fault_pending_wqh.lock);
+ spin_unlock_irq(&ctx->fault_pending_wqh.lock);
/* Flush pending events that may still wait on event_wqh */
wake_up_all(&ctx->event_wqh);
@@ -1135,7 +1145,7 @@ static ssize_t userfaultfd_ctx_read(stru
if (!ret && msg->event == UFFD_EVENT_FORK) {
ret = resolve_userfault_fork(ctx, fork_nctx, msg);
- spin_lock(&ctx->event_wqh.lock);
+ spin_lock_irq(&ctx->event_wqh.lock);
if (!list_empty(&fork_event)) {
/*
* The fork thread didn't abort, so we can
@@ -1181,7 +1191,7 @@ static ssize_t userfaultfd_ctx_read(stru
if (ret)
userfaultfd_ctx_put(fork_nctx);
}
- spin_unlock(&ctx->event_wqh.lock);
+ spin_unlock_irq(&ctx->event_wqh.lock);
}
return ret;
@@ -1220,14 +1230,14 @@ static ssize_t userfaultfd_read(struct f
static void __wake_userfault(struct userfaultfd_ctx *ctx,
struct userfaultfd_wake_range *range)
{
- spin_lock(&ctx->fault_pending_wqh.lock);
+ spin_lock_irq(&ctx->fault_pending_wqh.lock);
/* wake all in the range and autoremove */
if (waitqueue_active(&ctx->fault_pending_wqh))
__wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL,
range);
if (waitqueue_active(&ctx->fault_wqh))
__wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, range);
- spin_unlock(&ctx->fault_pending_wqh.lock);
+ spin_unlock_irq(&ctx->fault_pending_wqh.lock);
}
static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx,
@@ -1882,7 +1892,7 @@ static void userfaultfd_show_fdinfo(stru
wait_queue_entry_t *wq;
unsigned long pending = 0, total = 0;
- spin_lock(&ctx->fault_pending_wqh.lock);
+ spin_lock_irq(&ctx->fault_pending_wqh.lock);
list_for_each_entry(wq, &ctx->fault_pending_wqh.head, entry) {
pending++;
total++;
@@ -1890,7 +1900,7 @@ static void userfaultfd_show_fdinfo(stru
list_for_each_entry(wq, &ctx->fault_wqh.head, entry) {
total++;
}
- spin_unlock(&ctx->fault_pending_wqh.lock);
+ spin_unlock_irq(&ctx->fault_pending_wqh.lock);
/*
* If more protocols will be added, there will be all shown
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