Re: [Qemu-devel] [PATCH for 2.10 27/35] syscall: fix dereference of undefined pointer

[Philippe Mathieu-Daudé]

On 07/24/2017 04:33 PM, Laurent Vivier wrote:

Le 24/07/2017 à 20:27, Philippe Mathieu-Daudé a écrit :

Clang's scan-build-5.0 reports:

linux-user/syscall.c:5581:9: warning: Dereference of undefined pointer value
     if (*host_rt_dev_ptr != 0) {
         ^~~~~~~~~~~~~~~~

Reported-by: Clang Static Analyzer
Suggested-by: Laurent Vivier <lviv...@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <f4...@amsat.org>
---
  linux-user/syscall.c | 3 ++-
  1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index fcd20fa276..e79b5baec4 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -5524,7 +5524,7 @@ 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;

@@ -5570,6 +5570,7 @@ 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));

+    assert(host_rt_dev_ptr);
      if (*host_rt_dev_ptr != 0) {
          unlock_user((void *)*host_rt_dev_ptr,
                      *target_rt_dev_ptr, 0);

I think if you add the assert you should not have to add the "= NULL".
Could you check?

Indeed!

Thanks :)

Phil.