[Bug 111381] [CI][DRMTIP] igt at sw_sync@sync_multi_producer_single_consumer - incomplete - BUG: kernel NULL pointer dereference, address: 0000000000000000

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=111381

Chris Wilson <chris at chris-wilson.co.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #4 from Chris Wilson <chris at chris-wilson.co.uk> ---
commit d3c6dd1fb30d3853c2012549affe75c930f4a2f9 (HEAD -> drm-misc-next,
drm-misc/for-linux-next, drm-misc/drm-misc-next)
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Mon Aug 12 16:42:47 2019 +0100

    dma-buf/sw_sync: Synchronize signal vs syncpt free

    During release of the syncpt, we remove it from the list of syncpt and
    the tree, but only if it is not already been removed. However, during
    signaling, we first remove the syncpt from the list. So, if we
    concurrently free and signal the syncpt, the free may decide that it is
    not part of the tree and immediately free itself -- meanwhile the
    signaler goes on to use the now freed datastructure.

    In particular, we get struck by commit 0e2f733addbf ("dma-buf: make
    dma_fence structure a bit smaller v2") as the cb_list is immediately
    clobbered by the kfree_rcu.

    v2: Avoid calling into timeline_fence_release() from under the spinlock

    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111381
    Fixes: d3862e44daa7 ("dma-buf/sw-sync: Fix locking around sync_timeline
lists")
    References: 0e2f733addbf ("dma-buf: make dma_fence structure a bit smaller
v2")
    Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
    Cc: Sumit Semwal <sumit.semwal at linaro.org>
    Cc: Sean Paul <seanpaul at chromium.org>
    Cc: Gustavo Padovan <gustavo at padovan.org>
    Cc: Christian König <christian.koenig at amd.com>
    Cc: <stable at vger.kernel.org> # v4.14+
    Acked-by: Christian König <christian.koenig at amd.com>
    Link:
https://patchwork.freedesktop.org/patch/msgid/20190812154247.20508-1-chris@chris-wilson.co.uk

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