Messages in this thread | | | From | Niklas Cassel <> | Subject | Re: [PATCH] nvme: prevent double free in nvme_alloc_ns() error handling | Date | Mon, 27 Apr 2020 18:22:46 +0000 |
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On Mon, Apr 27, 2020 at 08:03:11PM +0200, Javier González wrote: > On 27.04.2020 14:34, Niklas Cassel wrote: > > When jumping to the out_put_disk label, we will call put_disk(), which will > > trigger a call to disk_release(), which calls blk_put_queue(). > > > > Later in the cleanup code, we do blk_cleanup_queue(), which will also call > > blk_put_queue(). > > > > Putting the queue twice is incorrect, and will generate a KASAN splat. > > > > Set the disk->queue pointer to NULL, before calling put_disk(), so that the > > first call to blk_put_queue() will not free the queue. > > > > The second call to blk_put_queue() uses another pointer to the same queue, > > so this call will still free the queue. > > > > Fixes: 85136c010285 ("lightnvm: simplify geometry enumeration") > > Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com> > > --- > > drivers/nvme/host/core.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c > > index 91c1bd659947..f2adea96b04c 100644 > > --- a/drivers/nvme/host/core.c > > +++ b/drivers/nvme/host/core.c > > @@ -3642,6 +3642,8 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid) > > > > return; > > out_put_disk: > > + /* prevent double queue cleanup */ > > + ns->disk->queue = NULL; > > put_disk(ns->disk); > > out_unlink_ns: > > mutex_lock(&ctrl->subsys->lock); > > -- > > 2.25.3 > > > What about delaying the assignment of ns->disk? > > diff --git i/drivers/nvme/host/core.c w/drivers/nvme/host/core.c > index a4d8c90ee7cc..6da4a9ced945 100644 > --- i/drivers/nvme/host/core.c > +++ w/drivers/nvme/host/core.c > @@ -3541,7 +3541,6 @@ static int nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid) > disk->queue = ns->queue; > disk->flags = flags; > memcpy(disk->disk_name, disk_name, DISK_NAME_LEN); > - ns->disk = disk; > > __nvme_revalidate_disk(disk, id); > > @@ -3553,6 +3552,8 @@ static int nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid) > } > } > > + ns->disk = disk; > +
Hello Javier!
The only case where we jump to the out_put_disk label, is if the nvme_nvm_register() call failed.
In that case, we want to undo the alloc_disk_node() operation, i.e., decrease the refcount.
If we don't set "ns->disk = disk;" before the call to nvme_nvm_register(), then, if register fails, and we jump to the put_disk(ns->disk) label, ns->disk will be NULL, so the recount will not be decreased, so I assume that this memory would then be a memory leak.
I think that the problem is that the block functions are a bit messy. Most drivers seem to do blk_cleanup_queue() first and then do put_disk(), but some drivers do it in the opposite way, so I think that we might have some more use-after-free bugs in some of these drivers that do it in the opposite way.
Kind regards, Niklas
> down_write(&ctrl->namespaces_rwsem); > list_add_tail(&ns->list, &ctrl->namespaces); > up_write(&ctrl->namespaces_rwsem); > > > Javier
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