| Message ID | 20171003104845.10417-2-hch@lst.de (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
On 10/03/2017 12:48 PM, Christoph Hellwig wrote: > From: Benjamin Block <bblock@linux.vnet.ibm.com> > > When under memory-pressure it is possible that the mempool which backs > the 'struct request_queue' will make use of up to BLKDEV_MIN_RQ count > emergency buffers - in case it can't get a regular allocation. These > buffers are preallocated and once they are also used, they are > re-supplied with old finished requests from the same request_queue (see > mempool_free()). > > The bug is, when re-supplying the emergency pool, the old requests are > not again ran through the callback mempool_t->alloc(), and thus also not > through the callback bsg_init_rq(). Thus we skip initialization, and > while the sense-buffer still should be good, scsi_request->cmd might > have become to be an invalid pointer in the meantime. When the request > is initialized in bsg.c, and the user's CDB is larger than BLK_MAX_CDB, > bsg will replace it with a custom allocated buffer, which is freed when > the user's command is finished, thus it dangles afterwards. When next a > command is sent by the user that has a smaller/similar CDB as > BLK_MAX_CDB, bsg will assume that scsi_request->cmd is backed by > scsi_request->__cmd, will not make a custom allocation, and write into > undefined memory. > > Fix this by splitting bsg_init_rq() into two functions: > - bsg_init_rq() is changed to only do the allocation of the > sense-buffer, which is used to back the bsg job's reply buffer. This > pointer should never change during the lifetime of a scsi_request, so > it doesn't need re-initialization. > - bsg_initialize_rq() is a new function that makes use of > 'struct request_queue's initialize_rq_fn callback (which was > introduced in v4.12). This is always called before the request is > given out via blk_get_request(). This function does the remaining > initialization that was previously done in bsg_init_rq(), and will > also do it when the request is taken from the emergency-pool of the > backing mempool. > > Fixes: 50b4d485528d ("bsg-lib: fix kernel panic resulting from missing allocation of reply-buffer") > Cc: <stable@vger.kernel.org> # 4.11+ > Reviewed-by: Christoph Hellwig <hch@lst.de> > Signed-off-by: Benjamin Block <bblock@linux.vnet.ibm.com> > --- > block/bsg-lib.c | 27 +++++++++++++++++++++------ > 1 file changed, 21 insertions(+), 6 deletions(-) > Reviewed-by: Hannes Reinecke <hare@suse.com> Cheers, Hannes
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
diff --git a/block/bsg-lib.c b/block/bsg-lib.c index dbddff8174e5..15d25ccd51a5 100644 --- a/block/bsg-lib.c +++ b/block/bsg-lib.c @@ -207,20 +207,34 @@ static int bsg_init_rq(struct request_queue *q, struct request *req, gfp_t gfp) struct bsg_job *job = blk_mq_rq_to_pdu(req); struct scsi_request *sreq = &job->sreq; + /* called right after the request is allocated for the request_queue */ + + sreq->sense = kzalloc(SCSI_SENSE_BUFFERSIZE, gfp); + if (!sreq->sense) + return -ENOMEM; + + return 0; +} + +static void bsg_initialize_rq(struct request *req) +{ + struct bsg_job *job = blk_mq_rq_to_pdu(req); + struct scsi_request *sreq = &job->sreq; + void *sense = sreq->sense; + + /* called right before the request is given to the request_queue user */ + memset(job, 0, sizeof(*job)); scsi_req_init(sreq); + + sreq->sense = sense; sreq->sense_len = SCSI_SENSE_BUFFERSIZE; - sreq->sense = kzalloc(sreq->sense_len, gfp); - if (!sreq->sense) - return -ENOMEM; job->req = req; - job->reply = sreq->sense; + job->reply = sense; job->reply_len = sreq->sense_len; job->dd_data = job + 1; - - return 0; } static void bsg_exit_rq(struct request_queue *q, struct request *req) @@ -251,6 +265,7 @@ struct request_queue *bsg_setup_queue(struct device *dev, const char *name, q->cmd_size = sizeof(struct bsg_job) + dd_job_size; q->init_rq_fn = bsg_init_rq; q->exit_rq_fn = bsg_exit_rq; + q->initialize_rq_fn = bsg_initialize_rq; q->request_fn = bsg_request_fn; ret = blk_init_allocated_queue(q);