[PATCH v3] nvme: Fix handling of large MDTS values

[PATCH v3] nvme: Fix handling of large MDTS values

[Bart Van Assche]

Instead of triggering an integer overflow and undefined behavior if MDTS is
large, set max_hw_sectors to UINT_MAX.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Sagi Grimberg <sagi@grimberg.me>
Cc: Keith Busch <kbusch@kernel.org>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---

Changes compared to v2: reduced the two max_hw_sectors = UINT_MAX statements into a single assignment.
Changes compared to v1: removed a dev_err() call.

 drivers/nvme/host/core.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 40215a0246e4..87d43309742b 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -3123,10 +3123,10 @@ static int nvme_init_identify(struct nvme_ctrl *ctrl)
 
 	atomic_set(&ctrl->abort_limit, id->acl + 1);
 	ctrl->vwc = id->vwc;
-	if (id->mdts)
-		max_hw_sectors = 1 << (id->mdts + page_shift - 9);
-	else
+	if (!id->mdts || check_shl_overflow(1U, id->mdts + page_shift - 9,
+					    &max_hw_sectors)) {
 		max_hw_sectors = UINT_MAX;
+	}
 	ctrl->max_hw_sectors =
 		min_not_zero(ctrl->max_hw_sectors, max_hw_sectors);
 

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Re: [PATCH v3] nvme: Fix handling of large MDTS values

[Keith Busch]

On Thu, Apr 01, 2021 at 06:39:07PM -0700, Bart Van Assche wrote:
> Instead of triggering an integer overflow and undefined behavior if MDTS is
> large, set max_hw_sectors to UINT_MAX.

Looks good,

Reviewed-by: Keith Busch <kbusch@kernel.org>

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Re: [PATCH v3] nvme: Fix handling of large MDTS values

[Damien Le Moal]

On 2021/04/02 10:47, Bart Van Assche wrote:
> Instead of triggering an integer overflow and undefined behavior if MDTS is
> large, set max_hw_sectors to UINT_MAX.
> 
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Sagi Grimberg <sagi@grimberg.me>
> Cc: Keith Busch <kbusch@kernel.org>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> ---
> 
> Changes compared to v2: reduced the two max_hw_sectors = UINT_MAX statements into a single assignment.
> Changes compared to v1: removed a dev_err() call.
> 
>  drivers/nvme/host/core.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index 40215a0246e4..87d43309742b 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -3123,10 +3123,10 @@ static int nvme_init_identify(struct nvme_ctrl *ctrl)
>  
>  	atomic_set(&ctrl->abort_limit, id->acl + 1);
>  	ctrl->vwc = id->vwc;
> -	if (id->mdts)
> -		max_hw_sectors = 1 << (id->mdts + page_shift - 9);
> -	else
> +	if (!id->mdts || check_shl_overflow(1U, id->mdts + page_shift - 9,
> +					    &max_hw_sectors)) {
>  		max_hw_sectors = UINT_MAX;
> +	}

Nit: this could be rewritten as:

	if (!id->mdts ||
	    check_shl_overflow(1U, id->mdts + page_shift - 9, &max_hw_sectors))
		max_hw_sectors = UINT_MAX;

More readable and no unneeded brackets. No ?

>  	ctrl->max_hw_sectors =
>  		min_not_zero(ctrl->max_hw_sectors, max_hw_sectors);
>  
> 
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> Linux-nvme@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-nvme
> 


-- 
Damien Le Moal
Western Digital Research

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Re: [PATCH v3] nvme: Fix handling of large MDTS values

[Christoph Hellwig]

On Fri, Apr 02, 2021 at 05:00:58AM +0000, Damien Le Moal wrote:
> On 2021/04/02 10:47, Bart Van Assche wrote:
> > Instead of triggering an integer overflow and undefined behavior if MDTS is
> > large, set max_hw_sectors to UINT_MAX.
> > 
> > Cc: Christoph Hellwig <hch@lst.de>
> > Cc: Sagi Grimberg <sagi@grimberg.me>
> > Cc: Keith Busch <kbusch@kernel.org>
> > Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> > ---
> > 
> > Changes compared to v2: reduced the two max_hw_sectors = UINT_MAX statements into a single assignment.
> > Changes compared to v1: removed a dev_err() call.
> > 
> >  drivers/nvme/host/core.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> > index 40215a0246e4..87d43309742b 100644
> > --- a/drivers/nvme/host/core.c
> > +++ b/drivers/nvme/host/core.c
> > @@ -3123,10 +3123,10 @@ static int nvme_init_identify(struct nvme_ctrl *ctrl)
> >  
> >  	atomic_set(&ctrl->abort_limit, id->acl + 1);
> >  	ctrl->vwc = id->vwc;
> > -	if (id->mdts)
> > -		max_hw_sectors = 1 << (id->mdts + page_shift - 9);
> > -	else
> > +	if (!id->mdts || check_shl_overflow(1U, id->mdts + page_shift - 9,
> > +					    &max_hw_sectors)) {
> >  		max_hw_sectors = UINT_MAX;
> > +	}
> 
> Nit: this could be rewritten as:
> 
> 	if (!id->mdts ||
> 	    check_shl_overflow(1U, id->mdts + page_shift - 9, &max_hw_sectors))
> 		max_hw_sectors = UINT_MAX;
> 
> More readable and no unneeded brackets. No ?

I'll just fix this up when applying the patch.

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Re: [PATCH v3] nvme: Fix handling of large MDTS values

[Christoph Hellwig]

Thanks,

applied to nvme-5.13.

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