[Qemu-devel] [PATCH] syscall: fix compiler warnings (clang 5)

[Qemu-devel] [PATCH] syscall: fix compiler warnings (clang 5)

[Philippe Mathieu-Daudé]

static code analyzer complain:

linux-user/syscall.c:5575:9: warning: Dereference of undefined pointer value
    if (*host_rt_dev_ptr != 0) {
        ^~~~~~~~~~~~~~~~

Reported-by: Clang Static Analyzer
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 linux-user/syscall.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index cec8428589..c541e22693 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -5526,7 +5526,7 @@ static abi_long do_ioctl_rt(const IOCTLEntry *ie, uint8_t *buf_temp,
     int target_size;
     void *argptr;
     abi_ulong *target_rt_dev_ptr;
-    unsigned long *host_rt_dev_ptr;
+    unsigned long *host_rt_dev_ptr = NULL;
     abi_long ret;
     int i;
 
@@ -5572,7 +5572,7 @@ static abi_long do_ioctl_rt(const IOCTLEntry *ie, uint8_t *buf_temp,
     unlock_user(argptr, arg, 0);
 
     ret = get_errno(safe_ioctl(fd, ie->host_cmd, buf_temp));
-    if (*host_rt_dev_ptr != 0) {
+    if (host_rt_dev_ptr != NULL && *host_rt_dev_ptr != 0) {
         unlock_user((void *)*host_rt_dev_ptr,
                     *target_rt_dev_ptr, 0);
     }
-- 
2.11.0

Re: [Qemu-devel] [PATCH] syscall: fix compiler warnings (clang 5)

[Laurent Vivier]

On 06/05/2017 02:41, Philippe Mathieu-Daudé wrote:
> static code analyzer complain:
> 
> linux-user/syscall.c:5575:9: warning: Dereference of undefined pointer value
>     if (*host_rt_dev_ptr != 0) {
>         ^~~~~~~~~~~~~~~~
> 
> Reported-by: Clang Static Analyzer
> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> ---
>  linux-user/syscall.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index cec8428589..c541e22693 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -5526,7 +5526,7 @@ static abi_long do_ioctl_rt(const IOCTLEntry *ie, uint8_t *buf_temp,
>      int target_size;
>      void *argptr;
>      abi_ulong *target_rt_dev_ptr;
> -    unsigned long *host_rt_dev_ptr;
> +    unsigned long *host_rt_dev_ptr = NULL;
>      abi_long ret;
>      int i;
>  
> @@ -5572,7 +5572,7 @@ static abi_long do_ioctl_rt(const IOCTLEntry *ie, uint8_t *buf_temp,
>      unlock_user(argptr, arg, 0);
>  
>      ret = get_errno(safe_ioctl(fd, ie->host_cmd, buf_temp));

I think we should "assert(host_rt_dev_ptr)" here. It's a bug if
host_rt_dev_ptr is not set.

The "for" loop scans the structure to find the rt_dev field, and we
should always enter in the first "if", so "host_rt_dev_ptr" is always set.

> -    if (*host_rt_dev_ptr != 0) {
> +    if (host_rt_dev_ptr != NULL && *host_rt_dev_ptr != 0) {
>          unlock_user((void *)*host_rt_dev_ptr,
>                      *target_rt_dev_ptr, 0);
>      }
> 

Laurent

Re: [Qemu-devel] [PATCH] syscall: fix compiler warnings (clang 5)

[Philippe Mathieu-Daudé]

On 05/10/2017 09:32 AM, Laurent Vivier wrote:
> On 06/05/2017 02:41, Philippe Mathieu-Daudé wrote:
>> static code analyzer complain:
>>
>> linux-user/syscall.c:5575:9: warning: Dereference of undefined pointer value
>>     if (*host_rt_dev_ptr != 0) {
>>         ^~~~~~~~~~~~~~~~
>>
>> Reported-by: Clang Static Analyzer
>> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
>> ---
>>  linux-user/syscall.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
>> index cec8428589..c541e22693 100644
>> --- a/linux-user/syscall.c
>> +++ b/linux-user/syscall.c
>> @@ -5526,7 +5526,7 @@ static abi_long do_ioctl_rt(const IOCTLEntry *ie, uint8_t *buf_temp,
>>      int target_size;
>>      void *argptr;
>>      abi_ulong *target_rt_dev_ptr;
>> -    unsigned long *host_rt_dev_ptr;
>> +    unsigned long *host_rt_dev_ptr = NULL;
>>      abi_long ret;
>>      int i;
>>
>> @@ -5572,7 +5572,7 @@ static abi_long do_ioctl_rt(const IOCTLEntry *ie, uint8_t *buf_temp,
>>      unlock_user(argptr, arg, 0);
>>
>>      ret = get_errno(safe_ioctl(fd, ie->host_cmd, buf_temp));
>
> I think we should "assert(host_rt_dev_ptr)" here. It's a bug if
> host_rt_dev_ptr is not set.
>
> The "for" loop scans the structure to find the rt_dev field, and we
> should always enter in the first "if", so "host_rt_dev_ptr" is always set.

It's better indeed, I'll use g_assert_nonnull() and resend.

Thanks!

>
>> -    if (*host_rt_dev_ptr != 0) {
>> +    if (host_rt_dev_ptr != NULL && *host_rt_dev_ptr != 0) {
>>          unlock_user((void *)*host_rt_dev_ptr,
>>                      *target_rt_dev_ptr, 0);
>>      }
>>
>
> Laurent
>

Re: [Qemu-devel] [PATCH] syscall: fix compiler warnings (clang 5)

[Eric Blake]

[-- Attachment #1: Type: text/plain, Size: 509 bytes --]


>>
>> The "for" loop scans the structure to find the rt_dev field, and we
>> should always enter in the first "if", so "host_rt_dev_ptr" is always
>> set.
> 
> It's better indeed, I'll use g_assert_nonnull() and resend.

Careful - we haven't yet resolved whether g_assert_nonnull() is safe to use.
https://lists.gnu.org/archive/html/qemu-devel/2017-04/msg05499.html

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 604 bytes --]