[v2] block: add IOC_PR_READ_KEYS and IOC_PR_READ_RESERVATION ioctls

[PATCH v2 2/4] nvme: reject invalid pr_read_keys() num_keys values

Posted by Stefan Hajnoczi 4 days, 5 hours ago

The pr_read_keys() interface has a u32 num_keys parameter. The NVMe
Reservation Report command has a u32 maximum length. Reject num_keys
values that are too large to fit.

This will become important when pr_read_keys() is exposed to untrusted
userspace via an <linux/pr.h> ioctl.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 drivers/nvme/host/pr.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/nvme/host/pr.c b/drivers/nvme/host/pr.c
index ca6a74607b139..156a2ae1fac2e 100644
--- a/drivers/nvme/host/pr.c
+++ b/drivers/nvme/host/pr.c
@@ -233,6 +233,10 @@ static int nvme_pr_read_keys(struct block_device *bdev,
 	int ret, i;
 	bool eds;
 
+	/* Check that keys fit into u32 rse_len */
+	if (num_keys > (U32_MAX - sizeof(*rse)) / sizeof(rse->regctl_eds[0]))
+		return -EINVAL;
+
 	/*
 	 * Assume we are using 128-bit host IDs and allocate a buffer large
 	 * enough to get enough keys to fill the return keys buffer.
-- 
2.52.0

Re: [PATCH v2 2/4] nvme: reject invalid pr_read_keys() num_keys values

Posted by Chaitanya Kulkarni 14 hours ago

On 11/27/25 07:54, Stefan Hajnoczi wrote:
> The pr_read_keys() interface has a u32 num_keys parameter. The NVMe
> Reservation Report command has a u32 maximum length. Reject num_keys
> values that are too large to fit.
>
> This will become important when pr_read_keys() is exposed to untrusted
> userspace via an <linux/pr.h> ioctl.
>
> Signed-off-by: Stefan Hajnoczi<stefanha@redhat.com>
> ---
>   drivers/nvme/host/pr.c | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/drivers/nvme/host/pr.c b/drivers/nvme/host/pr.c
> index ca6a74607b139..156a2ae1fac2e 100644
> --- a/drivers/nvme/host/pr.c
> +++ b/drivers/nvme/host/pr.c
> @@ -233,6 +233,10 @@ static int nvme_pr_read_keys(struct block_device *bdev,
>   	int ret, i;
>   	bool eds;
>   
> +	/* Check that keys fit into u32 rse_len */
> +	if (num_keys > (U32_MAX - sizeof(*rse)) / sizeof(rse->regctl_eds[0]))
> +		return -EINVAL;

de-referencing res in res->regctl_eds[0] is safe in this patch ?

if so please ignore this comment ...

-ck

Re: [PATCH v2 2/4] nvme: reject invalid pr_read_keys() num_keys values

Posted by Christoph Hellwig 14 hours ago

On Mon, Dec 01, 2025 at 07:11:31AM +0000, Chaitanya Kulkarni wrote:
> On 11/27/25 07:54, Stefan Hajnoczi wrote:
> > The pr_read_keys() interface has a u32 num_keys parameter. The NVMe
> > Reservation Report command has a u32 maximum length. Reject num_keys
> > values that are too large to fit.
> >
> > This will become important when pr_read_keys() is exposed to untrusted
> > userspace via an <linux/pr.h> ioctl.
> >
> > Signed-off-by: Stefan Hajnoczi<stefanha@redhat.com>
> > ---
> >   drivers/nvme/host/pr.c | 4 ++++
> >   1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/nvme/host/pr.c b/drivers/nvme/host/pr.c
> > index ca6a74607b139..156a2ae1fac2e 100644
> > --- a/drivers/nvme/host/pr.c
> > +++ b/drivers/nvme/host/pr.c
> > @@ -233,6 +233,10 @@ static int nvme_pr_read_keys(struct block_device *bdev,
> >   	int ret, i;
> >   	bool eds;
> >   
> > +	/* Check that keys fit into u32 rse_len */
> > +	if (num_keys > (U32_MAX - sizeof(*rse)) / sizeof(rse->regctl_eds[0]))
> > +		return -EINVAL;
> 
> de-referencing res in res->regctl_eds[0] is safe in this patch ?

sizeof does not dereference pointers in the expression.

Re: [PATCH v2 2/4] nvme: reject invalid pr_read_keys() num_keys values

Posted by Christoph Hellwig 14 hours ago

On Thu, Nov 27, 2025 at 10:54:22AM -0500, Stefan Hajnoczi wrote:
> The pr_read_keys() interface has a u32 num_keys parameter. The NVMe
> Reservation Report command has a u32 maximum length. Reject num_keys
> values that are too large to fit.
> 
> This will become important when pr_read_keys() is exposed to untrusted
> userspace via an <linux/pr.h> ioctl.
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  drivers/nvme/host/pr.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/nvme/host/pr.c b/drivers/nvme/host/pr.c
> index ca6a74607b139..156a2ae1fac2e 100644
> --- a/drivers/nvme/host/pr.c
> +++ b/drivers/nvme/host/pr.c
> @@ -233,6 +233,10 @@ static int nvme_pr_read_keys(struct block_device *bdev,
>  	int ret, i;
>  	bool eds;
>  
> +	/* Check that keys fit into u32 rse_len */
> +	if (num_keys > (U32_MAX - sizeof(*rse)) / sizeof(rse->regctl_eds[0]))
> +		return -EINVAL;
> +

We use struct_size to calculate the size below, which saturates on
overflow.  So just checking the rse_len variable returned by the that
would be nicer.  Bonus points for using sizeof_field() instead of
hardcoding U32_MAX.

Re: [PATCH v2 2/4] nvme: reject invalid pr_read_keys() num_keys values

Posted by Stefan Hajnoczi 5 hours ago

On Mon, Dec 01, 2025 at 07:36:49AM +0100, Christoph Hellwig wrote:
> On Thu, Nov 27, 2025 at 10:54:22AM -0500, Stefan Hajnoczi wrote:
> > The pr_read_keys() interface has a u32 num_keys parameter. The NVMe
> > Reservation Report command has a u32 maximum length. Reject num_keys
> > values that are too large to fit.
> > 
> > This will become important when pr_read_keys() is exposed to untrusted
> > userspace via an <linux/pr.h> ioctl.
> > 
> > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> > ---
> >  drivers/nvme/host/pr.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/drivers/nvme/host/pr.c b/drivers/nvme/host/pr.c
> > index ca6a74607b139..156a2ae1fac2e 100644
> > --- a/drivers/nvme/host/pr.c
> > +++ b/drivers/nvme/host/pr.c
> > @@ -233,6 +233,10 @@ static int nvme_pr_read_keys(struct block_device *bdev,
> >  	int ret, i;
> >  	bool eds;
> >  
> > +	/* Check that keys fit into u32 rse_len */
> > +	if (num_keys > (U32_MAX - sizeof(*rse)) / sizeof(rse->regctl_eds[0]))
> > +		return -EINVAL;
> > +
> 
> We use struct_size to calculate the size below, which saturates on
> overflow.  So just checking the rse_len variable returned by the that
> would be nicer.  Bonus points for using sizeof_field() instead of
> hardcoding U32_MAX.

Will fix. I don't see how to use sizeof_field() here, but taking
advantage of struct_size() already improves things a lot:

diff --git a/drivers/nvme/host/pr.c b/drivers/nvme/host/pr.c
index ca6a74607b139..ad2ecc2f49a97 100644
--- a/drivers/nvme/host/pr.c
+++ b/drivers/nvme/host/pr.c
@@ -228,7 +228,8 @@ static int nvme_pr_resv_report(struct block_device *bdev, void *data,
 static int nvme_pr_read_keys(struct block_device *bdev,
                struct pr_keys *keys_info)
 {
-       u32 rse_len, num_keys = keys_info->num_keys;
+       size_t rse_len;
+       u32 num_keys = keys_info->num_keys;
        struct nvme_reservation_status_ext *rse;
        int ret, i;
        bool eds;
@@ -238,6 +239,9 @@ static int nvme_pr_read_keys(struct block_device *bdev,
         * enough to get enough keys to fill the return keys buffer.
         */
        rse_len = struct_size(rse, regctl_eds, num_keys);
+       if (rse_len > U32_MAX)
+               return -EINVAL;
+
        rse = kzalloc(rse_len, GFP_KERNEL);
        if (!rse)
                return -ENOMEM;

Stefan

Re: [PATCH v2 2/4] nvme: reject invalid pr_read_keys() num_keys values

Posted by Hannes Reinecke 4 days, 3 hours ago

On 11/27/25 16:54, Stefan Hajnoczi wrote:
> The pr_read_keys() interface has a u32 num_keys parameter. The NVMe
> Reservation Report command has a u32 maximum length. Reject num_keys
> values that are too large to fit.
> 
> This will become important when pr_read_keys() is exposed to untrusted
> userspace via an <linux/pr.h> ioctl.
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>   drivers/nvme/host/pr.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 

Reviewed-by: Hannes Reinecke <hare@suse.de>
Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
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