linux-user: fix "may be used uninitialized" warnings

[Qemu-devel] [PATCH] linux-user: fix "may be used uninitialized" warnings

Posted by Marc-André Lureau 6 years, 8 months ago

Fixes:

/home/elmarco/src/qemu/linux-user/syscall.c: In function ‘do_ioctl_rt’:
/home/elmarco/src/qemu/linux-user/syscall.c:4773:9: error: ‘host_rt_dev_ptr’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
     if (*host_rt_dev_ptr != 0) {
         ^~~~~~~~~~~~~~~~
/home/elmarco/src/qemu/linux-user/syscall.c:4774:9: error: ‘target_rt_dev_ptr’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
         unlock_user((void *)*host_rt_dev_ptr,
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                     *target_rt_dev_ptr, 0);
                     ~~~~~~~~~~~~~~~~~~~~~~

Based on previous discussion from patch "linux-users/syscall: make
do_ioctl_rt safer" by Alex Bennée.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 linux-user/syscall.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 5bbb72f3d5..a15340b302 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -4723,8 +4723,8 @@ static abi_long do_ioctl_rt(const IOCTLEntry *ie, uint8_t *buf_temp,
     const int *dst_offsets, *src_offsets;
     int target_size;
     void *argptr;
-    abi_ulong *target_rt_dev_ptr;
-    unsigned long *host_rt_dev_ptr;
+    abi_ulong *target_rt_dev_ptr = NULL;
+    unsigned long *host_rt_dev_ptr = NULL;
     abi_long ret;
     int i;
 
@@ -4770,6 +4770,9 @@ 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 != NULL);
+    assert(target_rt_dev_ptr != NULL);
     if (*host_rt_dev_ptr != 0) {
         unlock_user((void *)*host_rt_dev_ptr,
                     *target_rt_dev_ptr, 0);
-- 
2.21.0

Re: [Qemu-devel] [PATCH] linux-user: fix "may be used uninitialized" warnings

Posted by Laurent Vivier 6 years, 8 months ago

On 05/03/2019 16:15, Marc-André Lureau wrote:
> Fixes:
> 
> /home/elmarco/src/qemu/linux-user/syscall.c: In function ‘do_ioctl_rt’:
> /home/elmarco/src/qemu/linux-user/syscall.c:4773:9: error: ‘host_rt_dev_ptr’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
>      if (*host_rt_dev_ptr != 0) {
>          ^~~~~~~~~~~~~~~~
> /home/elmarco/src/qemu/linux-user/syscall.c:4774:9: error: ‘target_rt_dev_ptr’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
>          unlock_user((void *)*host_rt_dev_ptr,
>          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>                      *target_rt_dev_ptr, 0);
>                      ~~~~~~~~~~~~~~~~~~~~~~
> 
> Based on previous discussion from patch "linux-users/syscall: make
> do_ioctl_rt safer" by Alex Bennée.
> 
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
>  linux-user/syscall.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index 5bbb72f3d5..a15340b302 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -4723,8 +4723,8 @@ static abi_long do_ioctl_rt(const IOCTLEntry *ie, uint8_t *buf_temp,
>      const int *dst_offsets, *src_offsets;
>      int target_size;
>      void *argptr;
> -    abi_ulong *target_rt_dev_ptr;
> -    unsigned long *host_rt_dev_ptr;
> +    abi_ulong *target_rt_dev_ptr = NULL;
> +    unsigned long *host_rt_dev_ptr = NULL;
>      abi_long ret;
>      int i;
>  
> @@ -4770,6 +4770,9 @@ 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 != NULL);
> +    assert(target_rt_dev_ptr != NULL);
>      if (*host_rt_dev_ptr != 0) {
>          unlock_user((void *)*host_rt_dev_ptr,
>                      *target_rt_dev_ptr, 0);
> 

Reviewed-by: Laurent Vivier <laurent@vivier.eu>