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    Subject[PATCH 5.18 091/231] xen/gntdev: Ignore failure to unmap INVALID_GRANT_HANDLE
    Date
    From: Demi Marie Obenour <demi@invisiblethingslab.com>

    [ Upstream commit 166d3863231667c4f64dee72b77d1102cdfad11f ]

    The error paths of gntdev_mmap() can call unmap_grant_pages() even
    though not all of the pages have been successfully mapped. This will
    trigger the WARN_ON()s in __unmap_grant_pages_done(). The number of
    warnings can be very large; I have observed thousands of lines of
    warnings in the systemd journal.

    Avoid this problem by only warning on unmapping failure if the handle
    being unmapped is not INVALID_GRANT_HANDLE. The handle field of any
    page that was not successfully mapped will be INVALID_GRANT_HANDLE, so
    this catches all cases where unmapping can legitimately fail.

    Fixes: dbe97cff7dd9 ("xen/gntdev: Avoid blocking in unmap_grant_pages()")
    Cc: stable@vger.kernel.org
    Suggested-by: Juergen Gross <jgross@suse.com>
    Signed-off-by: Demi Marie Obenour <demi@invisiblethingslab.com>
    Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
    Reviewed-by: Juergen Gross <jgross@suse.com>
    Link: https://lore.kernel.org/r/20220710230522.1563-1-demi@invisiblethingslab.com
    Signed-off-by: Juergen Gross <jgross@suse.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/xen/gntdev.c | 6 ++++--
    1 file changed, 4 insertions(+), 2 deletions(-)

    diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
    index 4b56c39f766d..84b143eef395 100644
    --- a/drivers/xen/gntdev.c
    +++ b/drivers/xen/gntdev.c
    @@ -396,13 +396,15 @@ static void __unmap_grant_pages_done(int result,
    unsigned int offset = data->unmap_ops - map->unmap_ops;

    for (i = 0; i < data->count; i++) {
    - WARN_ON(map->unmap_ops[offset+i].status);
    + WARN_ON(map->unmap_ops[offset + i].status != GNTST_okay &&
    + map->unmap_ops[offset + i].handle != INVALID_GRANT_HANDLE);
    pr_debug("unmap handle=%d st=%d\n",
    map->unmap_ops[offset+i].handle,
    map->unmap_ops[offset+i].status);
    map->unmap_ops[offset+i].handle = INVALID_GRANT_HANDLE;
    if (use_ptemod) {
    - WARN_ON(map->kunmap_ops[offset+i].status);
    + WARN_ON(map->kunmap_ops[offset + i].status != GNTST_okay &&
    + map->kunmap_ops[offset + i].handle != INVALID_GRANT_HANDLE);
    pr_debug("kunmap handle=%u st=%d\n",
    map->kunmap_ops[offset+i].handle,
    map->kunmap_ops[offset+i].status);
    --
    2.35.1


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