| Message ID | 20250314205033.762641-1-joannelkoong@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] fuse: fix uring race condition for null dereference of fc | expand |
On Fri, Mar 14, 2025 at 1:50 PM Joanne Koong <joannelkoong@gmail.com> wrote: > > There is a race condition leading to a kernel crash from a null > dereference when attemping to access fc->lock in > fuse_uring_create_queue(). fc may be NULL in the case where another > thread is creating the uring in fuse_uring_create() and has set > fc->ring but has not yet set ring->fc when fuse_uring_create_queue() > reads ring->fc. > > This fix passes fc to fuse_uring_create_queue() instead of accessing it > through ring->fc. > > Signed-off-by: Joanne Koong <joannelkoong@gmail.com> > Fixes: 24fe962c86f5 ("fuse: {io-uring} Handle SQEs - register commands") Thought I added the changelog between v1 -> v2 to the patch but I guess not. including it here now: Changes between v1 -> v2: * v1 implementation may be reordered by compiler (Bernd) * link to v1: https://lore.kernel.org/linux-fsdevel/20250314191334.215741-1-joannelkoong@gmail.com/ Thanks, Joanne > --- > fs/fuse/dev_uring.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/fs/fuse/dev_uring.c b/fs/fuse/dev_uring.c > index ab8c26042aa8..64f1ae308dc4 100644 > --- a/fs/fuse/dev_uring.c > +++ b/fs/fuse/dev_uring.c > @@ -250,10 +250,10 @@ static struct fuse_ring *fuse_uring_create(struct fuse_conn *fc) > return res; > } > > -static struct fuse_ring_queue *fuse_uring_create_queue(struct fuse_ring *ring, > +static struct fuse_ring_queue *fuse_uring_create_queue(struct fuse_conn *fc, > + struct fuse_ring *ring, > int qid) > { > - struct fuse_conn *fc = ring->fc; > struct fuse_ring_queue *queue; > struct list_head *pq; > > @@ -1088,7 +1088,7 @@ static int fuse_uring_register(struct io_uring_cmd *cmd, > > queue = ring->queues[qid]; > if (!queue) { > - queue = fuse_uring_create_queue(ring, qid); > + queue = fuse_uring_create_queue(fc, ring, qid); > if (!queue) > return err; > } > -- > 2.47.1 >
On 3/14/25 21:50, Joanne Koong wrote: > There is a race condition leading to a kernel crash from a null > dereference when attemping to access fc->lock in > fuse_uring_create_queue(). fc may be NULL in the case where another > thread is creating the uring in fuse_uring_create() and has set > fc->ring but has not yet set ring->fc when fuse_uring_create_queue() > reads ring->fc. > > This fix passes fc to fuse_uring_create_queue() instead of accessing it > through ring->fc. > > Signed-off-by: Joanne Koong <joannelkoong@gmail.com> > Fixes: 24fe962c86f5 ("fuse: {io-uring} Handle SQEs - register commands") > --- > fs/fuse/dev_uring.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/fs/fuse/dev_uring.c b/fs/fuse/dev_uring.c > index ab8c26042aa8..64f1ae308dc4 100644 > --- a/fs/fuse/dev_uring.c > +++ b/fs/fuse/dev_uring.c > @@ -250,10 +250,10 @@ static struct fuse_ring *fuse_uring_create(struct fuse_conn *fc) > return res; > } > > -static struct fuse_ring_queue *fuse_uring_create_queue(struct fuse_ring *ring, > +static struct fuse_ring_queue *fuse_uring_create_queue(struct fuse_conn *fc, > + struct fuse_ring *ring, > int qid) > { > - struct fuse_conn *fc = ring->fc; > struct fuse_ring_queue *queue; > struct list_head *pq; > > @@ -1088,7 +1088,7 @@ static int fuse_uring_register(struct io_uring_cmd *cmd, > > queue = ring->queues[qid]; > if (!queue) { > - queue = fuse_uring_create_queue(ring, qid); > + queue = fuse_uring_create_queue(fc, ring, qid); > if (!queue) > return err; > } I wonder if we could get more issues, fuse_uring_register() { struct fuse_ring *ring = smp_load_acquire(&fc->ring); ... if (qid >= ring->nr_queues) { ... } In fuse_uring_create() { ... fc->ring = ring; ring->nr_queues = nr_queues; ring->fc = fc; ring->max_payload_sz = max_payload_size; ... } I.e. we cannot trust any of the values assigned after fc->ring? Sorry about this, I should have noticed before :( Thanks, Bernd
diff --git a/fs/fuse/dev_uring.c b/fs/fuse/dev_uring.c index ab8c26042aa8..64f1ae308dc4 100644 --- a/fs/fuse/dev_uring.c +++ b/fs/fuse/dev_uring.c @@ -250,10 +250,10 @@ static struct fuse_ring *fuse_uring_create(struct fuse_conn *fc) return res; } -static struct fuse_ring_queue *fuse_uring_create_queue(struct fuse_ring *ring, +static struct fuse_ring_queue *fuse_uring_create_queue(struct fuse_conn *fc, + struct fuse_ring *ring, int qid) { - struct fuse_conn *fc = ring->fc; struct fuse_ring_queue *queue; struct list_head *pq; @@ -1088,7 +1088,7 @@ static int fuse_uring_register(struct io_uring_cmd *cmd, queue = ring->queues[qid]; if (!queue) { - queue = fuse_uring_create_queue(ring, qid); + queue = fuse_uring_create_queue(fc, ring, qid); if (!queue) return err; }
There is a race condition leading to a kernel crash from a null dereference when attemping to access fc->lock in fuse_uring_create_queue(). fc may be NULL in the case where another thread is creating the uring in fuse_uring_create() and has set fc->ring but has not yet set ring->fc when fuse_uring_create_queue() reads ring->fc. This fix passes fc to fuse_uring_create_queue() instead of accessing it through ring->fc. Signed-off-by: Joanne Koong <joannelkoong@gmail.com> Fixes: 24fe962c86f5 ("fuse: {io-uring} Handle SQEs - register commands") --- fs/fuse/dev_uring.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)