Re: [Qemu-devel] [PATVH v2] net: ne2000: fix bounds check in ioport operations

[Jason Wang <jasowang@redhat.com>]

On 12/31/2015 12:53 PM, P J P wrote:
> From: Prasad J Pandit <pjp@fedoraproject.org>
>
> While doing ioport r/w operations, ne2000 device emulation suffers
> from OOB r/w errors. Update respective array bounds check to avoid
> OOB access.
>
> Reported-by: Ling Liu <liuling-it@360.cn>
> Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
> ---
>  hw/net/ne2000.c | 28 +++++++++++++++-------------
>  1 file changed, 15 insertions(+), 13 deletions(-)
>
> Updated as per review in
>   -> https://lists.gnu.org/archive/html/qemu-devel/2015-12/msg04856.html
>
> diff --git a/hw/net/ne2000.c b/hw/net/ne2000.c
> index 010f9ef..d1f764b 100644
> --- a/hw/net/ne2000.c
> +++ b/hw/net/ne2000.c
> @@ -447,8 +447,7 @@ static uint32_t ne2000_ioport_read(void *opaque, uint32_t addr)
>  static inline void ne2000_mem_writeb(NE2000State *s, uint32_t addr,
>                                       uint32_t val)
>  {
> -    if (addr < 32 ||
> -        (addr >= NE2000_PMEM_START && addr < NE2000_MEM_SIZE)) {
> +    if (addr < 32 || (addr >= NE2000_PMEM_START && addr < NE2000_MEM_SIZE)) {

The change is unnecessary.

>          s->mem[addr] = val;
>      }
>  }
> @@ -457,9 +456,10 @@ static inline void ne2000_mem_writew(NE2000State *s, uint32_t addr,
>                                       uint32_t val)
>  {
>      addr &= ~1; /* XXX: check exact behaviour if not even */
> -    if (addr < 32 ||
> -        (addr >= NE2000_PMEM_START && addr < NE2000_MEM_SIZE)) {
> -        *(uint16_t *)(s->mem + addr) = cpu_to_le16(val);
> +    if (addr < 32
> +        || (addr >= NE2000_PMEM_START
> +            && addr + sizeof(uint16_t) < NE2000_MEM_SIZE)) {

I think you mean '<=' instead of '<' here? (And for the other checks below).

> +        *(uint16_t *)(s->mem + addr) = cpu_to_le16(data);
>      }
>  }
>  
> @@ -467,16 +467,16 @@ static inline void ne2000_mem_writel(NE2000State *s, uint32_t addr,
>                                       uint32_t val)
>  {
>      addr &= ~1; /* XXX: check exact behaviour if not even */
> -    if (addr < 32 ||
> -        (addr >= NE2000_PMEM_START && addr < NE2000_MEM_SIZE)) {
> +    if (addr < 32
> +        || (addr >= NE2000_PMEM_START
> +            && addr + sizeof(uint32_t) < NE2000_MEM_SIZE)) {
>          stl_le_p(s->mem + addr, val);
>      }
>  }
>  
>  static inline uint32_t ne2000_mem_readb(NE2000State *s, uint32_t addr)
>  {
> -    if (addr < 32 ||
> -        (addr >= NE2000_PMEM_START && addr < NE2000_MEM_SIZE)) {
> +    if (addr < 32 || (addr >= NE2000_PMEM_START && addr < NE2000_MEM_SIZE)) {
>          return s->mem[addr];
>      } else {
>          return 0xff;
> @@ -486,8 +486,9 @@ static inline uint32_t ne2000_mem_readb(NE2000State *s, uint32_t addr)
>  static inline uint32_t ne2000_mem_readw(NE2000State *s, uint32_t addr)
>  {
>      addr &= ~1; /* XXX: check exact behaviour if not even */
> -    if (addr < 32 ||
> -        (addr >= NE2000_PMEM_START && addr < NE2000_MEM_SIZE)) {
> +    if (addr < 32
> +        || (addr >= NE2000_PMEM_START
> +            && addr + sizeof(uint16_t) < NE2000_MEM_SIZE)) {
>          return le16_to_cpu(*(uint16_t *)(s->mem + addr));
>      } else {
>          return 0xffff;
> @@ -497,8 +498,9 @@ static inline uint32_t ne2000_mem_readw(NE2000State *s, uint32_t addr)
>  static inline uint32_t ne2000_mem_readl(NE2000State *s, uint32_t addr)
>  {
>      addr &= ~1; /* XXX: check exact behaviour if not even */
> -    if (addr < 32 ||
> -        (addr >= NE2000_PMEM_START && addr < NE2000_MEM_SIZE)) {
> +    if (addr < 32
> +        || (addr >= NE2000_PMEM_START
> +            && addr + sizeof(uint32_t) < NE2000_MEM_SIZE)) {
>          return ldl_le_p(s->mem + addr);
>      } else {
>          return 0xffffffff;