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    Subject[PATCH 4.8 123/140] ceph: fix error handling in ceph_read_iter
    Date
    4.8-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Nikolay Borisov <kernel@kyup.com>

    commit 0d7718f666be181fda1ba2d08f137d87c1419347 upstream.

    In case __ceph_do_getattr returns an error and the retry_op in
    ceph_read_iter is not READ_INLINE, then it's possible to invoke
    __free_page on a page which is NULL, this naturally leads to a crash.
    This can happen when, for example, a process waiting on a MDS reply
    receives sigterm.

    Fix this by explicitly checking whether the page is set or not.

    Signed-off-by: Nikolay Borisov <kernel@kyup.com>
    Reviewed-by: Yan, Zheng <zyan@redhat.com>
    Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/ceph/file.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    --- a/fs/ceph/file.c
    +++ b/fs/ceph/file.c
    @@ -1272,7 +1272,8 @@ again:
    statret = __ceph_do_getattr(inode, page,
    CEPH_STAT_CAP_INLINE_DATA, !!page);
    if (statret < 0) {
    - __free_page(page);
    + if (page)
    + __free_page(page);
    if (statret == -ENODATA) {
    BUG_ON(retry_op != READ_INLINE);
    goto again;

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