Re: [PATCH v2 1/7] dmaengine: idxd: fix memory leak in error handling path of idxd_setup_wqs

[Shuai Xue <xueshuai@xxxxxxxxxxxxxxxxx>]

在 2025/2/19 00:32, Fenghua Yu 写道:
> Hi, Shuai,
>
> On 2/14/25 21:44, Shuai Xue wrote:
> > Memory allocated for wqs is not freed if an error occurs during
> > idxd_setup_wqs(). To fix it, free the allocated memory in the reverse
> > order of allocation before exiting the function in case of an error.
> >
> > Fixes: a8563a33a5e2 ("dmanegine: idxd: reformat opcap output to match bitmap_parse() input")
> > Signed-off-by: Shuai Xue <xueshuai@xxxxxxxxxxxxxxxxx>
> > Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>
> > ---
> >   drivers/dma/idxd/init.c | 20 +++++++++++++++++---
> >   1 file changed, 17 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
> > index b946f78f85e1..b85736fd25bd 100644
> > --- a/drivers/dma/idxd/init.c
> > +++ b/drivers/dma/idxd/init.c
> > @@ -169,8 +169,8 @@ static int idxd_setup_wqs(struct idxd_device *idxd)
> >       idxd->wq_enable_map = bitmap_zalloc_node(idxd->max_wqs, GFP_KERNEL, dev_to_node(dev));
> >       if (!idxd->wq_enable_map) {
> > -        kfree(idxd->wqs);
> > -        return -ENOMEM;
> > +        rc = -ENOMEM;
> > +        goto err_bitmap;
> >       }
> >       for (i = 0; i < idxd->max_wqs; i++) {
> > @@ -191,6 +191,7 @@ static int idxd_setup_wqs(struct idxd_device *idxd)
> >           rc = dev_set_name(conf_dev, "wq%d.%d", idxd->id, wq->id);
> >           if (rc < 0) {
> >               put_device(conf_dev);
> > +            kfree(wq);
> >               goto err;
> >           }
> > @@ -204,6 +205,7 @@ static int idxd_setup_wqs(struct idxd_device *idxd)
> >           wq->wqcfg = kzalloc_node(idxd->wqcfg_size, GFP_KERNEL, dev_to_node(dev));
> >           if (!wq->wqcfg) {
> >               put_device(conf_dev);
> > +            kfree(wq);
> >               rc = -ENOMEM;
> >               goto err;
> >           }
> > @@ -211,7 +213,9 @@ static int idxd_setup_wqs(struct idxd_device *idxd)
> >           if (idxd->hw.wq_cap.op_config) {
> >               wq->opcap_bmap = bitmap_zalloc(IDXD_MAX_OPCAP_BITS, GFP_KERNEL);
> >               if (!wq->opcap_bmap) {
> > +                kfree(wq->wqcfg);
> >                   put_device(conf_dev);
> > +                kfree(wq);
> >                   rc = -ENOMEM;
> >                   goto err;
> >               }
> > @@ -225,11 +229,21 @@ static int idxd_setup_wqs(struct idxd_device *idxd)
> >       return 0;
> >    err:
> > -    while (--i >= 0) {
> > +    while (i-- > 0) {
>
> Why changed to "i-- > 0" here? Before coming to here, the mem areas allocated for wqs[i] are freed already and there is not need to free them again here, right? 

Yes.

> And if i>1, mem areas for wqs[0] won't be freed and will leak, right?

No, the two ways of writing are equivalent.

#include <stdio.h>

int main()
{
    int i = 1;
    while (i-- > 0)
        printf("freeing i %d\n", i);

    return 0;
}

// console output
// freeing i 0

I will drop this line to avoid confusion.

Thanks.
Shuai