diff options
| author | Bart Van Assche <bvanassche@acm.org> | 2023-03-14 11:21:54 -0700 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2023-03-14 19:20:48 -0600 |
| commit | 9b0cb770f5d7b1ff40bea7ca385438ee94570eec (patch) | |
| tree | 3c6a907cc5d5dde18a91df6dc36e4b7106a4f33c /drivers/block/loop.c | |
| parent | 34e0a279a993debaff03158fc2fbf6a00c093643 (diff) | |
| download | linux-9b0cb770f5d7b1ff40bea7ca385438ee94570eec.tar.gz | |
loop: Fix use-after-free issues
do_req_filebacked() calls blk_mq_complete_request() synchronously or
asynchronously when using asynchronous I/O unless memory allocation fails.
Hence, modify loop_handle_cmd() such that it does not dereference 'cmd' nor
'rq' after do_req_filebacked() finished unless we are sure that the request
has not yet been completed. This patch fixes the following kernel crash:
Unable to handle kernel NULL pointer dereference at virtual address 0000000000000054
Call trace:
css_put.42938+0x1c/0x1ac
loop_process_work+0xc8c/0xfd4
loop_rootcg_workfn+0x24/0x34
process_one_work+0x244/0x558
worker_thread+0x400/0x8fc
kthread+0x16c/0x1e0
ret_from_fork+0x10/0x20
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Dan Schatzberg <schatzberg.dan@gmail.com>
Fixes: c74d40e8b5e2 ("loop: charge i/o to mem and blk cg")
Fixes: bc07c10a3603 ("block: loop: support DIO & AIO")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20230314182155.80625-1-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'drivers/block/loop.c')
| -rw-r--r-- | drivers/block/loop.c | 25 |
1 files changed, 17 insertions, 8 deletions
diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 839373451c2b7d..28eb59fd71ca23 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1859,35 +1859,44 @@ static blk_status_t loop_queue_rq(struct blk_mq_hw_ctx *hctx, static void loop_handle_cmd(struct loop_cmd *cmd) { + struct cgroup_subsys_state *cmd_blkcg_css = cmd->blkcg_css; + struct cgroup_subsys_state *cmd_memcg_css = cmd->memcg_css; struct request *rq = blk_mq_rq_from_pdu(cmd); const bool write = op_is_write(req_op(rq)); struct loop_device *lo = rq->q->queuedata; int ret = 0; struct mem_cgroup *old_memcg = NULL; + const bool use_aio = cmd->use_aio; if (write && (lo->lo_flags & LO_FLAGS_READ_ONLY)) { ret = -EIO; goto failed; } - if (cmd->blkcg_css) - kthread_associate_blkcg(cmd->blkcg_css); - if (cmd->memcg_css) + if (cmd_blkcg_css) + kthread_associate_blkcg(cmd_blkcg_css); + if (cmd_memcg_css) old_memcg = set_active_memcg( - mem_cgroup_from_css(cmd->memcg_css)); + mem_cgroup_from_css(cmd_memcg_css)); + /* + * do_req_filebacked() may call blk_mq_complete_request() synchronously + * or asynchronously if using aio. Hence, do not touch 'cmd' after + * do_req_filebacked() has returned unless we are sure that 'cmd' has + * not yet been completed. + */ ret = do_req_filebacked(lo, rq); - if (cmd->blkcg_css) + if (cmd_blkcg_css) kthread_associate_blkcg(NULL); - if (cmd->memcg_css) { + if (cmd_memcg_css) { set_active_memcg(old_memcg); - css_put(cmd->memcg_css); + css_put(cmd_memcg_css); } failed: /* complete non-aio request */ - if (!cmd->use_aio || ret) { + if (!use_aio || ret) { if (ret == -EOPNOTSUPP) cmd->ret = ret; else |