Re: [PATCH 3/8] vhost: vringh: use krealloc_array()
On Tue, Oct 27, 2020 at 6:08 PM Joe Perches wrote:
>
> On Tue, 2020-10-27 at 17:58 +0100, Bartosz Golaszewski wrote:
> > On Tue, Oct 27, 2020 at 5:50 PM Joe Perches wrote:
> > >
> > > On Tue, 2020-10-27 at 11:28 -0400, Michael S. Tsirkin wrote:
> > > > On Tue, Oct 27, 2020 at 01:17:20PM +0100, Bartosz Golaszewski wrote:
> > > > > From: Bartosz Golaszewski
> > > > >
> > > > > Use the helper that checks for overflows internally instead of
> > > > > manually
> > > > > calculating the size of the new array.
> > > > >
> > > > > Signed-off-by: Bartosz Golaszewski
> > > >
> > > > No problem with the patch, it does introduce some symmetry in the code.
> > >
> > > Perhaps more symmetry by using kmemdup
> > > ---
> > > drivers/vhost/vringh.c | 23 ++-
> > > 1 file changed, 10 insertions(+), 13 deletions(-)
> > >
> > > diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
> > > index 8bd8b403f087..99222a3651cd 100644
> > > --- a/drivers/vhost/vringh.c
> > > +++ b/drivers/vhost/vringh.c
> > > @@ -191,26 +191,23 @@ static int move_to_indirect(const struct vringh
> > > *vrh,
> > > static int resize_iovec(struct vringh_kiov *iov, gfp_t gfp)
> > > {
> > > struct kvec *new;
> > > - unsigned int flag, new_num = (iov->max_num &
> > > ~VRINGH_IOV_ALLOCATED) * 2;
> > > + size_t new_num = (iov->max_num & ~VRINGH_IOV_ALLOCATED) * 2;
> > > + size_t size;
> > >
> > > if (new_num < 8)
> > > new_num = 8;
> > >
> > > - flag = (iov->max_num & VRINGH_IOV_ALLOCATED);
> > > - if (flag)
> > > - new = krealloc(iov->iov, new_num * sizeof(struct iovec),
> > > gfp);
> > > - else {
> > > - new = kmalloc_array(new_num, sizeof(struct iovec), gfp);
> > > - if (new) {
> > > - memcpy(new, iov->iov,
> > > - iov->max_num * sizeof(struct iovec));
> > > - flag = VRINGH_IOV_ALLOCATED;
> > > - }
> > > - }
> > > + if (unlikely(check_mul_overflow(new_num, sizeof(struct iovec),
> > > )))
> > > + return -ENOMEM;
> > > +
> >
> > The whole point of using helpers such as kmalloc_array() is not doing
> > these checks manually.
>
> Tradeoffs for in readability for overflow and not mistyping or doing
> the multiplication of iov->max_num * sizeof(struct iovec) twice.
>
It's out of scope for this series - I want to add users for
krealloc_array(), not refactor code I don't really know. If the
maintainer of this bit objects, it can be dropped.
> Just fyi:
>
> the realloc doesn't do a multiplication overflow test as written so the
> suggestion is slightly more resistant to defect.
>
I'm not sure what your point is. I used krealloc_array() exactly for
this reason - to add the overflow test.
BTW I suppose kmalloc_array() here can be replaced with
krealloc_array() if the original pointer is NULL the first time it's
called.
Bartosz
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Re: [PATCH 3/8] vhost: vringh: use krealloc_array()
On Tue, Oct 27, 2020 at 5:50 PM Joe Perches wrote:
>
> On Tue, 2020-10-27 at 11:28 -0400, Michael S. Tsirkin wrote:
> > On Tue, Oct 27, 2020 at 01:17:20PM +0100, Bartosz Golaszewski wrote:
> > > From: Bartosz Golaszewski
> > >
> > > Use the helper that checks for overflows internally instead of manually
> > > calculating the size of the new array.
> > >
> > > Signed-off-by: Bartosz Golaszewski
> >
> > No problem with the patch, it does introduce some symmetry in the code.
>
> Perhaps more symmetry by using kmemdup
> ---
> drivers/vhost/vringh.c | 23 ++-
> 1 file changed, 10 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
> index 8bd8b403f087..99222a3651cd 100644
> --- a/drivers/vhost/vringh.c
> +++ b/drivers/vhost/vringh.c
> @@ -191,26 +191,23 @@ static int move_to_indirect(const struct vringh *vrh,
> static int resize_iovec(struct vringh_kiov *iov, gfp_t gfp)
> {
> struct kvec *new;
> - unsigned int flag, new_num = (iov->max_num & ~VRINGH_IOV_ALLOCATED) *
> 2;
> + size_t new_num = (iov->max_num & ~VRINGH_IOV_ALLOCATED) * 2;
> + size_t size;
>
> if (new_num < 8)
> new_num = 8;
>
> - flag = (iov->max_num & VRINGH_IOV_ALLOCATED);
> - if (flag)
> - new = krealloc(iov->iov, new_num * sizeof(struct iovec), gfp);
> - else {
> - new = kmalloc_array(new_num, sizeof(struct iovec), gfp);
> - if (new) {
> - memcpy(new, iov->iov,
> - iov->max_num * sizeof(struct iovec));
> - flag = VRINGH_IOV_ALLOCATED;
> - }
> - }
> + if (unlikely(check_mul_overflow(new_num, sizeof(struct iovec),
> )))
> + return -ENOMEM;
> +
The whole point of using helpers such as kmalloc_array() is not doing
these checks manually.
Bartosz
> + if (iov->max_num & VRINGH_IOV_ALLOCATED)
> + new = krealloc(iov->iov, size, gfp);
> + else
> + new = kmemdup(iov->iov, size, gfp);
> if (!new)
> return -ENOMEM;
> iov->iov = new;
> - iov->max_num = (new_num | flag);
> + iov->max_num = new_num | VRINGH_IOV_ALLOCATED;
> return 0;
> }
>
>
>
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[PATCH 3/8] vhost: vringh: use krealloc_array()
From: Bartosz Golaszewski
Use the helper that checks for overflows internally instead of manually
calculating the size of the new array.
Signed-off-by: Bartosz Golaszewski
---
drivers/vhost/vringh.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
index 8bd8b403f087..08a0e1c842df 100644
--- a/drivers/vhost/vringh.c
+++ b/drivers/vhost/vringh.c
@@ -198,7 +198,8 @@ static int resize_iovec(struct vringh_kiov *iov, gfp_t gfp)
flag = (iov->max_num & VRINGH_IOV_ALLOCATED);
if (flag)
- new = krealloc(iov->iov, new_num * sizeof(struct iovec), gfp);
+ new = krealloc_array(iov->iov, new_num,
+sizeof(struct iovec), gfp);
else {
new = kmalloc_array(new_num, sizeof(struct iovec), gfp);
if (new) {
--
2.29.1
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Re: [PATCH 3/8] vhost: vringh: use krealloc_array()
On Tue, 2020-10-27 at 17:58 +0100, Bartosz Golaszewski wrote:
> On Tue, Oct 27, 2020 at 5:50 PM Joe Perches wrote:
> >
> > On Tue, 2020-10-27 at 11:28 -0400, Michael S. Tsirkin wrote:
> > > On Tue, Oct 27, 2020 at 01:17:20PM +0100, Bartosz Golaszewski wrote:
> > > > From: Bartosz Golaszewski
> > > >
> > > > Use the helper that checks for overflows internally instead of manually
> > > > calculating the size of the new array.
> > > >
> > > > Signed-off-by: Bartosz Golaszewski
> > >
> > > No problem with the patch, it does introduce some symmetry in the code.
> >
> > Perhaps more symmetry by using kmemdup
> > ---
> > drivers/vhost/vringh.c | 23 ++-
> > 1 file changed, 10 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
> > index 8bd8b403f087..99222a3651cd 100644
> > --- a/drivers/vhost/vringh.c
> > +++ b/drivers/vhost/vringh.c
> > @@ -191,26 +191,23 @@ static int move_to_indirect(const struct vringh *vrh,
> > static int resize_iovec(struct vringh_kiov *iov, gfp_t gfp)
> > {
> > struct kvec *new;
> > - unsigned int flag, new_num = (iov->max_num & ~VRINGH_IOV_ALLOCATED)
> > * 2;
> > + size_t new_num = (iov->max_num & ~VRINGH_IOV_ALLOCATED) * 2;
> > + size_t size;
> >
> > if (new_num < 8)
> > new_num = 8;
> >
> > - flag = (iov->max_num & VRINGH_IOV_ALLOCATED);
> > - if (flag)
> > - new = krealloc(iov->iov, new_num * sizeof(struct iovec),
> > gfp);
> > - else {
> > - new = kmalloc_array(new_num, sizeof(struct iovec), gfp);
> > - if (new) {
> > - memcpy(new, iov->iov,
> > - iov->max_num * sizeof(struct iovec));
> > - flag = VRINGH_IOV_ALLOCATED;
> > - }
> > - }
> > + if (unlikely(check_mul_overflow(new_num, sizeof(struct iovec),
> > )))
> > + return -ENOMEM;
> > +
>
> The whole point of using helpers such as kmalloc_array() is not doing
> these checks manually.
Tradeoffs for in readability for overflow and not mistyping or doing
the multiplication of iov->max_num * sizeof(struct iovec) twice.
Just fyi:
the realloc doesn't do a multiplication overflow test as written so the
suggestion is slightly more resistant to defect.
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Re: [PATCH 3/8] vhost: vringh: use krealloc_array()
On Tue, 2020-10-27 at 11:28 -0400, Michael S. Tsirkin wrote:
> On Tue, Oct 27, 2020 at 01:17:20PM +0100, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski
> >
> > Use the helper that checks for overflows internally instead of manually
> > calculating the size of the new array.
> >
> > Signed-off-by: Bartosz Golaszewski
>
> No problem with the patch, it does introduce some symmetry in the code.
Perhaps more symmetry by using kmemdup
---
drivers/vhost/vringh.c | 23 ++-
1 file changed, 10 insertions(+), 13 deletions(-)
diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
index 8bd8b403f087..99222a3651cd 100644
--- a/drivers/vhost/vringh.c
+++ b/drivers/vhost/vringh.c
@@ -191,26 +191,23 @@ static int move_to_indirect(const struct vringh *vrh,
static int resize_iovec(struct vringh_kiov *iov, gfp_t gfp)
{
struct kvec *new;
- unsigned int flag, new_num = (iov->max_num & ~VRINGH_IOV_ALLOCATED) * 2;
+ size_t new_num = (iov->max_num & ~VRINGH_IOV_ALLOCATED) * 2;
+ size_t size;
if (new_num < 8)
new_num = 8;
- flag = (iov->max_num & VRINGH_IOV_ALLOCATED);
- if (flag)
- new = krealloc(iov->iov, new_num * sizeof(struct iovec), gfp);
- else {
- new = kmalloc_array(new_num, sizeof(struct iovec), gfp);
- if (new) {
- memcpy(new, iov->iov,
- iov->max_num * sizeof(struct iovec));
- flag = VRINGH_IOV_ALLOCATED;
- }
- }
+ if (unlikely(check_mul_overflow(new_num, sizeof(struct iovec), )))
+ return -ENOMEM;
+
+ if (iov->max_num & VRINGH_IOV_ALLOCATED)
+ new = krealloc(iov->iov, size, gfp);
+ else
+ new = kmemdup(iov->iov, size, gfp);
if (!new)
return -ENOMEM;
iov->iov = new;
- iov->max_num = (new_num | flag);
+ iov->max_num = new_num | VRINGH_IOV_ALLOCATED;
return 0;
}
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Re: [PATCH 3/8] vhost: vringh: use krealloc_array()
On Tue, Oct 27, 2020 at 01:17:20PM +0100, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski
>
> Use the helper that checks for overflows internally instead of manually
> calculating the size of the new array.
>
> Signed-off-by: Bartosz Golaszewski
No problem with the patch, it does introduce some symmetry in the code.
Acked-by: Michael S. Tsirkin
> ---
> drivers/vhost/vringh.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
> index 8bd8b403f087..08a0e1c842df 100644
> --- a/drivers/vhost/vringh.c
> +++ b/drivers/vhost/vringh.c
> @@ -198,7 +198,8 @@ static int resize_iovec(struct vringh_kiov *iov, gfp_t
> gfp)
>
> flag = (iov->max_num & VRINGH_IOV_ALLOCATED);
> if (flag)
> - new = krealloc(iov->iov, new_num * sizeof(struct iovec), gfp);
> + new = krealloc_array(iov->iov, new_num,
> + sizeof(struct iovec), gfp);
> else {
> new = kmalloc_array(new_num, sizeof(struct iovec), gfp);
> if (new) {
> --
> 2.29.1
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