[Qemu-devel] [PATCH] hmp: fix "info cpu" segfault

[Qemu-devel] [PATCH] hmp: fix "info cpu" segfault

[Iwona Kotlarska]

Running "dump-guest-memory /dev/null 0 8192" results in segfault.
Fix by checking if we have CPU.

Signed-off-by: Iwona Kotlarska <iwona260909@gmail.com>
---
 target/i386/arch_dump.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/target/i386/arch_dump.c b/target/i386/arch_dump.c
index 5a2e4be5d0..45cda6afb1 100644
--- a/target/i386/arch_dump.c
+++ b/target/i386/arch_dump.c
@@ -390,9 +390,10 @@ int cpu_get_dump_info(ArchDumpInfo *info,
     GuestPhysBlock *block;
 
 #ifdef TARGET_X86_64
-    X86CPU *first_x86_cpu = X86_CPU(first_cpu);
-
-    lma = !!(first_x86_cpu->env.hflags & HF_LMA_MASK);
+    X86CPU *first_x86_cpu = NULL;
+    first_x86_cpu = X86_CPU(first_cpu);
+    if (first_cpu != NULL)
+        lma = !!(first_x86_cpu->env.hflags & HF_LMA_MASK);
 #endif
 
     if (lma) {
-- 
2.12.0

Re: [Qemu-devel] [PATCH] hmp: fix "info cpu" segfault

[Marcel Apfelbaum]

On 03/29/2017 07:52 PM, Iwona Kotlarska wrote:
> Running "dump-guest-memory /dev/null 0 8192" results in segfault.
> Fix by checking if we have CPU.
>

Hi Iwona,
Thank you for contributing to the QEMU project.

Please state the whole command line that causes the problem,
not only the hmp command:

    Running QEMU with "qemu-system-x86_64 -M none -nographic -m 256"
    and executing  "dump-guest-memory /dev/null 0 8192" results in segfault.
    Fix this by...

> Signed-off-by: Iwona Kotlarska <iwona260909@gmail.com>
> ---
>  target/i386/arch_dump.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/target/i386/arch_dump.c b/target/i386/arch_dump.c
> index 5a2e4be5d0..45cda6afb1 100644
> --- a/target/i386/arch_dump.c
> +++ b/target/i386/arch_dump.c
> @@ -390,9 +390,10 @@ int cpu_get_dump_info(ArchDumpInfo *info,
>      GuestPhysBlock *block;
>
>  #ifdef TARGET_X86_64
> -    X86CPU *first_x86_cpu = X86_CPU(first_cpu);
> -
> -    lma = !!(first_x86_cpu->env.hflags & HF_LMA_MASK);
> +    X86CPU *first_x86_cpu = NULL;
> +    first_x86_cpu = X86_CPU(first_cpu);

You didn't need to break the above in two lines,
but is not a big issue either.

> +    if (first_cpu != NULL)
> +        lma = !!(first_x86_cpu->env.hflags & HF_LMA_MASK);

Please run: ./scripts/checkpatch.pl on the patch before you
submit to ensure coding style.
   You will see that we always use if { }; the patch has "DOS line endings".


You are welcome to submit the patch again.
In the meantime:
     Tested-by: Marcel Apfelbaum <marcel@redhat.com>

Thanks,
Marcel

>  #endif
>
>      if (lma) {
>

--