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

[Jason Wang <jasowang@redhat.com>]

On 12/30/2015 03:44 PM, P J P wrote:
> From: Prasad J Pandit <pjp@fedoraproject.org>
>
> While doing ioport r/w oprations, ne2000 device emulation suffers
> from OOB r/w error. 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 | 34 ++++++++++++++++++++--------------
>  1 file changed, 20 insertions(+), 14 deletions(-)
>
> diff --git a/hw/net/ne2000.c b/hw/net/ne2000.c
> index 010f9ef..42e4804 100644
> --- a/hw/net/ne2000.c
> +++ b/hw/net/ne2000.c
> @@ -447,9 +447,10 @@ 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)) {
> -        s->mem[addr] = val;
> +    if (addr < 32
> +        || (addr >= NE2000_PMEM_START
> +            && addr <= NE2000_MEM_SIZE - sizeof(uint8_t))) {

Patch makes sense just the check looks odd. I'd prefer something like:

uint8_t data = val;

if (... || addr + sizeof(data) <= NE2000_MEM_SIZE)

Thanks


> +        s->mem[addr] = (uint8_t)val;
>      }
>  }
>  
> @@ -457,8 +458,9 @@ 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)) {
> +    if (addr < 32
> +        || (addr >= NE2000_PMEM_START
> +            && addr <= NE2000_MEM_SIZE - sizeof(uint16_t))) {
>          *(uint16_t *)(s->mem + addr) = cpu_to_le16(val);
>      }
>  }
> @@ -467,17 +469,19 @@ 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 <= NE2000_MEM_SIZE - sizeof(uint32_t))) {
>          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)) {
> -        return s->mem[addr];
> +    if (addr < 32
> +        || (addr >= NE2000_PMEM_START
> +            && addr <= NE2000_MEM_SIZE - sizeof(uint8_t))) {
> +        return (uint8_t)s->mem[addr];
>      } else {
>          return 0xff;
>      }
> @@ -486,8 +490,9 @@ 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 <= NE2000_MEM_SIZE - sizeof(uint16_t))) {
>          return le16_to_cpu(*(uint16_t *)(s->mem + addr));
>      } else {
>          return 0xffff;
> @@ -497,8 +502,9 @@ 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 <= NE2000_MEM_SIZE - sizeof(uint32_t))) {
>          return ldl_le_p(s->mem + addr);
>      } else {
>          return 0xffffffff;