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userfaultfd: disable irqs when taking the waitqueue lock

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userfaultfd contains howe-grown locking of the waitqueue lock, and does
not disable interrupts.  This relies on the fact that no one else takes it
from interrupt context and violates an invariat of the normal waitqueue
locking scheme.  With aio poll it is easy to trigger other locks that
disable interrupts (or are called from interrupt context).

Link: http://lkml.kernel.org/r/20181018154101.18750-1-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: <stable@vger.kernel.org>	[4.19.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Christoph Hellwig 2018-10-26 15:02:19 -07:00 committed by Linus Torvalds
parent fa76da461b
commit ae62c16e10
1 changed files with 4 additions and 4 deletions
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8
fs/userfaultfd.c
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@ -1026,7 +1026,7 @@ static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait,
struct userfaultfd_ctx *fork_nctx = NULL;
/* always take the fd_wqh lock before the fault_pending_wqh lock */
spin_lock(&ctx->fd_wqh.lock);
spin_lock_irq(&ctx->fd_wqh.lock);
__add_wait_queue(&ctx->fd_wqh, &wait);
for (;;) {
set_current_state(TASK_INTERRUPTIBLE);
@ -1112,13 +1112,13 @@ static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait,
ret = -EAGAIN;
break;
}
spin_unlock(&ctx->fd_wqh.lock);
spin_unlock_irq(&ctx->fd_wqh.lock);
schedule();
spin_lock(&ctx->fd_wqh.lock);
spin_lock_irq(&ctx->fd_wqh.lock);
}
__remove_wait_queue(&ctx->fd_wqh, &wait);
__set_current_state(TASK_RUNNING);
spin_unlock(&ctx->fd_wqh.lock);
spin_unlock_irq(&ctx->fd_wqh.lock);
if (!ret && msg->event == UFFD_EVENT_FORK) {
ret = resolve_userfault_fork(ctx, fork_nctx, msg);