[Qemu-devel] [PATCH] slirp/arp_table.c: Avoid shifting into sign bit of signed integers

[Qemu-devel] [PATCH] slirp/arp_table.c: Avoid shifting into sign bit of signed integers

[Peter Maydell]

"0xf << 28" shifts right into the sign bit, since 0xf is a signed
integer. Use the 'U' suffix to force an unsigned shift to avoid
this undefined behaviour and a clang sanitizer warning.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 slirp/arp_table.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/slirp/arp_table.c b/slirp/arp_table.c
index bf698c1..ecdb0ba 100644
--- a/slirp/arp_table.c
+++ b/slirp/arp_table.c
@@ -38,7 +38,7 @@ void arp_table_add(Slirp *slirp, uint32_t ip_addr, uint8_t ethaddr[ETH_ALEN])
                 ethaddr[3], ethaddr[4], ethaddr[5]));
 
     /* Check 0.0.0.0/8 invalid source-only addresses */
-    if ((ip_addr & htonl(~(0xf << 28))) == 0) {
+    if ((ip_addr & htonl(~(0xfU << 28))) == 0) {
         return;
     }
 
@@ -74,7 +74,7 @@ bool arp_table_search(Slirp *slirp, uint32_t ip_addr,
     DEBUG_ARG("ip = 0x%x", ip_addr);
 
     /* Check 0.0.0.0/8 invalid source-only addresses */
-    assert((ip_addr & htonl(~(0xf << 28))) != 0);
+    assert((ip_addr & htonl(~(0xfU << 28))) != 0);
 
     /* If broadcast address */
     if (ip_addr == 0xffffffff || ip_addr == broadcast_addr) {
-- 
1.7.9.5

Re: [Qemu-devel] [PATCH] slirp/arp_table.c: Avoid shifting into sign bit of signed integers

[Eric Blake]

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On 08/23/2013 10:36 AM, Peter Maydell wrote:
> "0xf << 28" shifts right into the sign bit, since 0xf is a signed
> integer. Use the 'U' suffix to force an unsigned shift to avoid
> this undefined behaviour and a clang sanitizer warning.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  slirp/arp_table.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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Re: [Qemu-devel] [PATCH] slirp/arp_table.c: Avoid shifting into sign bit of signed integers

[Jan Kiszka]

On 2013-08-23 18:36, Peter Maydell wrote:
> "0xf << 28" shifts right into the sign bit, since 0xf is a signed
> integer. Use the 'U' suffix to force an unsigned shift to avoid
> this undefined behaviour and a clang sanitizer warning.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  slirp/arp_table.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/slirp/arp_table.c b/slirp/arp_table.c
> index bf698c1..ecdb0ba 100644
> --- a/slirp/arp_table.c
> +++ b/slirp/arp_table.c
> @@ -38,7 +38,7 @@ void arp_table_add(Slirp *slirp, uint32_t ip_addr, uint8_t ethaddr[ETH_ALEN])
>                  ethaddr[3], ethaddr[4], ethaddr[5]));
>  
>      /* Check 0.0.0.0/8 invalid source-only addresses */
> -    if ((ip_addr & htonl(~(0xf << 28))) == 0) {
> +    if ((ip_addr & htonl(~(0xfU << 28))) == 0) {
>          return;
>      }
>  
> @@ -74,7 +74,7 @@ bool arp_table_search(Slirp *slirp, uint32_t ip_addr,
>      DEBUG_ARG("ip = 0x%x", ip_addr);
>  
>      /* Check 0.0.0.0/8 invalid source-only addresses */
> -    assert((ip_addr & htonl(~(0xf << 28))) != 0);
> +    assert((ip_addr & htonl(~(0xfU << 28))) != 0);
>  
>      /* If broadcast address */
>      if (ip_addr == 0xffffffff || ip_addr == broadcast_addr) {
> 

Acked-by: Jan Kiszka <jan.kiszka@siemens.com>

-- 
Siemens AG, Corporate Technology, CT RTC ITP SES-DE
Corporate Competence Center Embedded Linux

Re: [Qemu-devel] [Qemu-trivial] [PATCH] slirp/arp_table.c: Avoid shifting into sign bit of signed integers

[Michael Tokarev]

23.08.2013 20:36, Peter Maydell wrote:
> "0xf << 28" shifts right into the sign bit, since 0xf is a signed
> integer. Use the 'U' suffix to force an unsigned shift to avoid
> this undefined behaviour and a clang sanitizer warning.

Thanks, applied to the trivial-patches queue.

/mjt