staging: vc04_services: prevent integer overflow in create_pagelist()

commit ca641bae6da977d638458e78cd1487b6160a2718 upstream.

The create_pagelist() "count" parameter comes from the user in
vchiq_ioctl() and it could overflow.  If you look at how create_page()
is called in vchiq_prepare_bulk_data(), then the "size" variable is an
int so it doesn't make sense to allow negatives or larger than INT_MAX.

I don't know this code terribly well, but I believe that typical values
of "count" are typically quite low and I don't think this check will
affect normal valid uses at all.

The "pagelist_size" calculation can also overflow on 32 bit systems, but
not on 64 bit systems.  I have added an integer overflow check for that
as well.

The Raspberry PI doesn't offer the same level of memory protection that
x86 does so these sorts of bugs are probably not super critical to fix.

Fixes: 71bad7f08641 ("staging: add bcm2708 vchiq driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c
index f72eebc71dd83ff3513d374711f8f12912a28d67..94590ac5b3cf1b3b3aca151e45e658c545101f7a 100644 (file)
--- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c
+++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c
@@ -381,9 +381,18 @@ create_pagelist(char __user *buf, size_t count, unsigned short type,
        int run, addridx, actual_pages;
         unsigned long *need_release;
 
+       if (count >= INT_MAX - PAGE_SIZE)
+               return NULL;
+
        offset = (unsigned int)buf & (PAGE_SIZE - 1);
        num_pages = (count + offset + PAGE_SIZE - 1) / PAGE_SIZE;
 
+       if (num_pages > (SIZE_MAX - sizeof(PAGELIST_T) -
+                        sizeof(struct vchiq_pagelist_info)) /
+                       (sizeof(u32) + sizeof(pages[0]) +
+                        sizeof(struct scatterlist)))
+               return NULL;
+
        *ppagelist = NULL;
 
        /* Allocate enough storage to hold the page pointers and the page