2019-07-11 07:37:15

by Wenwen Wang

Subject: [PATCH] block/bio-integrity: fix a memory leak bug

From: Wenwen Wang <[email protected]>

In bio_integrity_prep(), a kernel buffer is allocated through kmalloc() to
hold integrity metadata. Later on, the buffer will be attached to the bio
structure through bio_integrity_add_page(), which returns the number of
bytes of integrity metadata attached. Due to unexpected situations,
bio_integrity_add_page() may return 0. As a result, bio_integrity_prep()
needs to be terminated with 'false' returned to indicate this error.
However, the allocated kernel buffer is not freed on this execution path,
leading to a memory leak.

To fix this issue, free the allocated buffer before returning from
bio_integrity_prep().

Signed-off-by: Wenwen Wang <[email protected]>
---
block/bio-integrity.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/block/bio-integrity.c b/block/bio-integrity.c
index 4db6208..bfae10c 100644
--- a/block/bio-integrity.c
+++ b/block/bio-integrity.c
@@ -276,8 +276,10 @@ bool bio_integrity_prep(struct bio *bio)
ret = bio_integrity_add_page(bio, virt_to_page(buf),
bytes, offset);

- if (ret == 0)
+ if (ret == 0) {
+ kfree(buf);
return false;
+ }

if (ret < bytes)
break;
--
2.7.4

2019-07-11 09:22:43

by Ming Lei

Subject: Re: [PATCH] block/bio-integrity: fix a memory leak bug

On Thu, Jul 11, 2019 at 3:36 PM Wenwen Wang <[email protected]> wrote:
>
> From: Wenwen Wang <[email protected]>
>
> In bio_integrity_prep(), a kernel buffer is allocated through kmalloc() to
> hold integrity metadata. Later on, the buffer will be attached to the bio
> structure through bio_integrity_add_page(), which returns the number of
> bytes of integrity metadata attached. Due to unexpected situations,
> bio_integrity_add_page() may return 0. As a result, bio_integrity_prep()
> needs to be terminated with 'false' returned to indicate this error.
> However, the allocated kernel buffer is not freed on this execution path,
> leading to a memory leak.
>
> To fix this issue, free the allocated buffer before returning from
> bio_integrity_prep().
>
> Signed-off-by: Wenwen Wang <[email protected]>
> ---
> block/bio-integrity.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/block/bio-integrity.c b/block/bio-integrity.c
> index 4db6208..bfae10c 100644
> --- a/block/bio-integrity.c
> +++ b/block/bio-integrity.c
> @@ -276,8 +276,10 @@ bool bio_integrity_prep(struct bio *bio)
> ret = bio_integrity_add_page(bio, virt_to_page(buf),
> bytes, offset);
>
> - if (ret == 0)
> + if (ret == 0) {
> + kfree(buf);
> return false;
> + }

This way may not be enough, and the bio payload needs to be freed.

And you may refer to the error handling for 'IS_ERR(bip)', and bio->bi_status
needs to be set, and bio_endio() needs to be called too.


Thanks,
Ming Lei

2019-07-11 20:02:30

by Wenwen Wang

Subject: Re: [PATCH] block/bio-integrity: fix a memory leak bug

On Thu, Jul 11, 2019 at 4:22 AM Ming Lei <[email protected]> wrote:
>
> On Thu, Jul 11, 2019 at 3:36 PM Wenwen Wang <[email protected]> wrote:
> >
> > From: Wenwen Wang <[email protected]>
> >
> > In bio_integrity_prep(), a kernel buffer is allocated through kmalloc() to
> > hold integrity metadata. Later on, the buffer will be attached to the bio
> > structure through bio_integrity_add_page(), which returns the number of
> > bytes of integrity metadata attached. Due to unexpected situations,
> > bio_integrity_add_page() may return 0. As a result, bio_integrity_prep()
> > needs to be terminated with 'false' returned to indicate this error.
> > However, the allocated kernel buffer is not freed on this execution path,
> > leading to a memory leak.
> >
> > To fix this issue, free the allocated buffer before returning from
> > bio_integrity_prep().
> >
> > Signed-off-by: Wenwen Wang <[email protected]>
> > ---
> > block/bio-integrity.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/block/bio-integrity.c b/block/bio-integrity.c
> > index 4db6208..bfae10c 100644
> > --- a/block/bio-integrity.c
> > +++ b/block/bio-integrity.c
> > @@ -276,8 +276,10 @@ bool bio_integrity_prep(struct bio *bio)
> > ret = bio_integrity_add_page(bio, virt_to_page(buf),
> > bytes, offset);
> >
> > - if (ret == 0)
> > + if (ret == 0) {
> > + kfree(buf);
> > return false;
> > + }
>
> This way may not be enough, and the bio payload needs to be freed.
>
> And you may refer to the error handling for 'IS_ERR(bip)', and bio->bi_status
> needs to be set, and bio_endio() needs to be called too.

Thanks for your comments! I will rework the patch.

Wenwen