The error exit of privcmd_ioctl_dm_op() is calling unlock_pages()
potentially with pages being NULL, leading to a NULL dereference.
Fix that by calling unlock_pages only if lock_pages() was at least
partially successful.
Cc: <[email protected]>
Fixes: ab520be8cd5d ("xen/privcmd: Add IOCTL_PRIVCMD_DM_OP")
Reported-by: Rustam Subkhankulov <[email protected]>
Signed-off-by: Juergen Gross <[email protected]>
---
drivers/xen/privcmd.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index 3369734108af..ec87968b4459 100644
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -679,7 +679,7 @@ static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)
rc = lock_pages(kbufs, kdata.num, pages, nr_pages, &pinned);
if (rc < 0) {
nr_pages = pinned;
- goto out;
+ goto unlock;
}
for (i = 0; i < kdata.num; i++) {
@@ -691,8 +691,9 @@ static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)
rc = HYPERVISOR_dm_op(kdata.dom, kdata.num, xbufs);
xen_preemptible_hcall_end();
-out:
+ unlock:
unlock_pages(pages, nr_pages);
+ out:
kfree(xbufs);
kfree(pages);
kfree(kbufs);
--
2.35.3
On 24.08.22 17:26, Juergen Gross wrote:
Hello Juergen
> The error exit of privcmd_ioctl_dm_op() is calling unlock_pages()
> potentially with pages being NULL, leading to a NULL dereference.
>
> Fix that by calling unlock_pages only if lock_pages() was at least
> partially successful.
>
> Cc: <[email protected]>
> Fixes: ab520be8cd5d ("xen/privcmd: Add IOCTL_PRIVCMD_DM_OP")
> Reported-by: Rustam Subkhankulov <[email protected]>
> Signed-off-by: Juergen Gross <[email protected]>
Reviewed-by: Oleksandr Tyshchenko <[email protected]>
> ---
> drivers/xen/privcmd.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
> index 3369734108af..ec87968b4459 100644
> --- a/drivers/xen/privcmd.c
> +++ b/drivers/xen/privcmd.c
> @@ -679,7 +679,7 @@ static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)
> rc = lock_pages(kbufs, kdata.num, pages, nr_pages, &pinned);
> if (rc < 0) {
> nr_pages = pinned;
> - goto out;
> + goto unlock;
> }
>
> for (i = 0; i < kdata.num; i++) {
> @@ -691,8 +691,9 @@ static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)
> rc = HYPERVISOR_dm_op(kdata.dom, kdata.num, xbufs);
> xen_preemptible_hcall_end();
>
> -out:
> + unlock:
> unlock_pages(pages, nr_pages);
> + out:
> kfree(xbufs);
> kfree(pages);
> kfree(kbufs);
--
Regards,
Oleksandr Tyshchenko
On 25.08.22 09:38, Jan Beulich wrote:
> On 24.08.2022 16:26, Juergen Gross wrote:
>> The error exit of privcmd_ioctl_dm_op() is calling unlock_pages()
>> potentially with pages being NULL, leading to a NULL dereference.
>>
>> Fix that by calling unlock_pages only if lock_pages() was at least
>> partially successful.
>>
>> Cc: <[email protected]>
>> Fixes: ab520be8cd5d ("xen/privcmd: Add IOCTL_PRIVCMD_DM_OP")
>> Reported-by: Rustam Subkhankulov <[email protected]>
>> Signed-off-by: Juergen Gross <[email protected]>
>
> Reviewed-by: Jan Beulich <[email protected]>
> albeit I wonder whether you did consider the variant actually
> reducing code size (and avoiding the need for yet another label),
> ...
>
>> --- a/drivers/xen/privcmd.c
>> +++ b/drivers/xen/privcmd.c
>> @@ -679,7 +679,7 @@ static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)
>> rc = lock_pages(kbufs, kdata.num, pages, nr_pages, &pinned);
>> if (rc < 0) {
>> nr_pages = pinned;
>
> ... dropping this line and ...
>
>> - goto out;
>> + goto unlock;
>> }
>>
>> for (i = 0; i < kdata.num; i++) {
>> @@ -691,8 +691,9 @@ static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)
>> rc = HYPERVISOR_dm_op(kdata.dom, kdata.num, xbufs);
>> xen_preemptible_hcall_end();
>>
>> -out:
>> + unlock:
>> unlock_pages(pages, nr_pages);
>
> ... passing "pinned" here.
Looking into this I found another problem: NOT using pinned is wrong, as
lock_pages() doesn't guarantee that all pages were really locked. I think
lock_pages() should return an error, in case pin_user_pages_fast() didn't
lock as many pages es expected.
Juergen
On 24.08.2022 16:26, Juergen Gross wrote:
> The error exit of privcmd_ioctl_dm_op() is calling unlock_pages()
> potentially with pages being NULL, leading to a NULL dereference.
>
> Fix that by calling unlock_pages only if lock_pages() was at least
> partially successful.
>
> Cc: <[email protected]>
> Fixes: ab520be8cd5d ("xen/privcmd: Add IOCTL_PRIVCMD_DM_OP")
> Reported-by: Rustam Subkhankulov <[email protected]>
> Signed-off-by: Juergen Gross <[email protected]>
Reviewed-by: Jan Beulich <[email protected]>
albeit I wonder whether you did consider the variant actually
reducing code size (and avoiding the need for yet another label),
...
> --- a/drivers/xen/privcmd.c
> +++ b/drivers/xen/privcmd.c
> @@ -679,7 +679,7 @@ static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)
> rc = lock_pages(kbufs, kdata.num, pages, nr_pages, &pinned);
> if (rc < 0) {
> nr_pages = pinned;
... dropping this line and ...
> - goto out;
> + goto unlock;
> }
>
> for (i = 0; i < kdata.num; i++) {
> @@ -691,8 +691,9 @@ static long privcmd_ioctl_dm_op(struct file *file, void __user *udata)
> rc = HYPERVISOR_dm_op(kdata.dom, kdata.num, xbufs);
> xen_preemptible_hcall_end();
>
> -out:
> + unlock:
> unlock_pages(pages, nr_pages);
... passing "pinned" here.
Jan
> + out:
> kfree(xbufs);
> kfree(pages);
> kfree(kbufs);