lkml.org 
[lkml]   [2014]   [Oct]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 3.16 313/357] blk-mq: Avoid race condition with uninitialized requests
    Date
    3.16-stable review patch.  If anyone has any objections, please let me know.

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

    From: David Hildenbrand <dahi@linux.vnet.ibm.com>

    commit 683d0e126232d898a481daa3a4ca032c2b1a9660 upstream.

    This patch should fix the bug reported in
    https://lkml.org/lkml/2014/9/11/249.

    We have to initialize at least the atomic_flags and the cmd_flags when
    allocating storage for the requests.

    Otherwise blk_mq_timeout_check() might dereference uninitialized
    pointers when racing with the creation of a request.

    Also move the reset of cmd_flags for the initializing code to the point
    where a request is freed. So we will never end up with pending flush
    request indicators that might trigger dereferences of invalid pointers
    in blk_mq_timeout_check().

    Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
    Reported-by: Paulo De Rezende Pinatti <ppinatti@linux.vnet.ibm.com>
    Tested-by: Paulo De Rezende Pinatti <ppinatti@linux.vnet.ibm.com>
    Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
    Signed-off-by: Jens Axboe <axboe@fb.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    block/blk-mq.c | 4 +++-
    1 file changed, 3 insertions(+), 1 deletion(-)

    --- a/block/blk-mq.c
    +++ b/block/blk-mq.c
    @@ -219,7 +219,6 @@ __blk_mq_alloc_request(struct blk_mq_all
    if (tag != BLK_MQ_TAG_FAIL) {
    rq = data->hctx->tags->rqs[tag];

    - rq->cmd_flags = 0;
    if (blk_mq_tag_busy(data->hctx)) {
    rq->cmd_flags = REQ_MQ_INFLIGHT;
    atomic_inc(&data->hctx->nr_active);
    @@ -274,6 +273,7 @@ static void __blk_mq_free_request(struct

    if (rq->cmd_flags & REQ_MQ_INFLIGHT)
    atomic_dec(&hctx->nr_active);
    + rq->cmd_flags = 0;

    clear_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
    blk_mq_put_tag(hctx, tag, &ctx->last_tag);
    @@ -1411,6 +1411,8 @@ static struct blk_mq_tags *blk_mq_init_r
    left -= to_do * rq_size;
    for (j = 0; j < to_do; j++) {
    tags->rqs[i] = p;
    + tags->rqs[i]->atomic_flags = 0;
    + tags->rqs[i]->cmd_flags = 0;
    if (set->ops->init_request) {
    if (set->ops->init_request(set->driver_data,
    tags->rqs[i], hctx_idx, i,



    \
     
     \ /
      Last update: 2014-10-04 02:01    [W:4.280 / U:0.900 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site