drivers/virt/fsl_hypervisor.c: prevent integer overflow in ioctl

The "param.count" value is a u64 thatcomes from the user.  The code
later in the function assumes that param.count is at least one and if
it's not then it leads to an Oops when we dereference the ZERO_SIZE_PTR.

Also the addition can have an integer overflow which would lead us to
allocate a smaller "pages" array than required.  I can't immediately
tell what the possible run times implications are, but it's safest to
prevent the overflow.

Link: http://lkml.kernel.org/r/20181218082129.GE32567@kadam
Fixes: 6db7199407ca ("drivers/virt: introduce Freescale hypervisor management driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Timur Tabi <timur@freescale.com>
Cc: Mihai Caraman <mihai.caraman@freescale.com>
Cc: Kumar Gala <galak@kernel.crashing.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/virt/fsl_hypervisor.c b/drivers/virt/fsl_hypervisor.c
index a41431edbf25c63a934edec8c9c6f1d6bc241b84..93d5bebf9572a4892c3375f592812eb81b9caf58 100644 (file)
--- a/drivers/virt/fsl_hypervisor.c
+++ b/drivers/virt/fsl_hypervisor.c
@@ -215,6 +215,9 @@ static long ioctl_memcpy(struct fsl_hv_ioctl_memcpy __user *p)
         * hypervisor.
         */
        lb_offset = param.local_vaddr & (PAGE_SIZE - 1);
+       if (param.count == 0 ||
+           param.count > U64_MAX - lb_offset - PAGE_SIZE + 1)
+               return -EINVAL;
        num_pages = (param.count + lb_offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
 
        /* Allocate the buffers we need */