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SubjectRe: WARNING in cma_exit_net
On Mon, Apr 01, 2019 at 10:36:05AM -0700, syzbot wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: e3ecb83e Add linux-next specific files for 20190401
> git tree: linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=13bc36cd200000
> kernel config: https://syzkaller.appspot.com/x/.config?x=db6c9f2bfeb91a99
> dashboard link: https://syzkaller.appspot.com/bug?extid=2e3e485d5697ea610460
> compiler: gcc (GCC) 9.0.0 20181231 (experimental)
>
> Unfortunately, I don't have any reproducer for this crash yet.
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+2e3e485d5697ea610460@syzkaller.appspotmail.com
>
> WARNING: CPU: 1 PID: 7 at drivers/infiniband/core/cma.c:4674
> cma_exit_net+0x327/0x390 drivers/infiniband/core/cma.c:4674
> Kernel panic - not syncing: panic_on_warn set ...

Matt: This is why the WARN_ON(!xa_empty()) is so valuable. Magically
syzkaller can find something in this code is buggy.

Mellanox is also showing a different testing failure over the weekend
(use after free or something) from your 'cma: Convert portspace IDRs
to XArray'

If you seem something obvious wrong in that patch please speak
up.. Below is what I applied.

Thanks,
Jason

diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
index 68c997be242930..a8b9c66c85252b 100644
--- a/drivers/infiniband/core/cma.c
+++ b/drivers/infiniband/core/cma.c
@@ -39,7 +39,7 @@
#include <linux/mutex.h>
#include <linux/random.h>
#include <linux/igmp.h>
-#include <linux/idr.h>
+#include <linux/xarray.h>
#include <linux/inetdevice.h>
#include <linux/slab.h>
#include <linux/module.h>
@@ -191,10 +191,10 @@ static struct workqueue_struct *cma_wq;
static unsigned int cma_pernet_id;

struct cma_pernet {
- struct idr tcp_ps;
- struct idr udp_ps;
- struct idr ipoib_ps;
- struct idr ib_ps;
+ struct xarray tcp_ps;
+ struct xarray udp_ps;
+ struct xarray ipoib_ps;
+ struct xarray ib_ps;
};

static struct cma_pernet *cma_pernet(struct net *net)
@@ -202,7 +202,8 @@ static struct cma_pernet *cma_pernet(struct net *net)
return net_generic(net, cma_pernet_id);
}

-static struct idr *cma_pernet_idr(struct net *net, enum rdma_ucm_port_space ps)
+static
+struct xarray *cma_pernet_xa(struct net *net, enum rdma_ucm_port_space ps)
{
struct cma_pernet *pernet = cma_pernet(net);

@@ -247,25 +248,25 @@ struct class_port_info_context {
static int cma_ps_alloc(struct net *net, enum rdma_ucm_port_space ps,
struct rdma_bind_list *bind_list, int snum)
{
- struct idr *idr = cma_pernet_idr(net, ps);
+ struct xarray *xa = cma_pernet_xa(net, ps);

- return idr_alloc(idr, bind_list, snum, snum + 1, GFP_KERNEL);
+ return xa_insert(xa, snum, bind_list, GFP_KERNEL);
}

static struct rdma_bind_list *cma_ps_find(struct net *net,
enum rdma_ucm_port_space ps, int snum)
{
- struct idr *idr = cma_pernet_idr(net, ps);
+ struct xarray *xa = cma_pernet_xa(net, ps);

- return idr_find(idr, snum);
+ return xa_load(xa, snum);
}

static void cma_ps_remove(struct net *net, enum rdma_ucm_port_space ps,
int snum)
{
- struct idr *idr = cma_pernet_idr(net, ps);
+ struct xarray *xa = cma_pernet_xa(net, ps);

- idr_remove(idr, snum);
+ xa_erase(xa, snum);
}

enum {
@@ -4655,10 +4656,10 @@ static int cma_init_net(struct net *net)
{
struct cma_pernet *pernet = cma_pernet(net);

- idr_init(&pernet->tcp_ps);
- idr_init(&pernet->udp_ps);
- idr_init(&pernet->ipoib_ps);
- idr_init(&pernet->ib_ps);
+ xa_init(&pernet->tcp_ps);
+ xa_init(&pernet->udp_ps);
+ xa_init(&pernet->ipoib_ps);
+ xa_init(&pernet->ib_ps);

return 0;
}
@@ -4667,10 +4668,10 @@ static void cma_exit_net(struct net *net)
{
struct cma_pernet *pernet = cma_pernet(net);

- idr_destroy(&pernet->tcp_ps);
- idr_destroy(&pernet->udp_ps);
- idr_destroy(&pernet->ipoib_ps);
- idr_destroy(&pernet->ib_ps);
+ WARN_ON(!xa_empty(&pernet->tcp_ps));
+ WARN_ON(!xa_empty(&pernet->udp_ps));
+ WARN_ON(!xa_empty(&pernet->ipoib_ps));
+ WARN_ON(!xa_empty(&pernet->ib_ps));
}

static struct pernet_operations cma_pernet_operations = {
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