[Qemu-devel] [PATCH] linux-user/elfload.c: Don't memset(NULL..) if malloc() failed

[Qemu-devel] [PATCH] linux-user/elfload.c: Don't memset(NULL..) if malloc() failed

[Peter Maydell]

If a malloc() in copy_elf_strings() failed we would call memset()
before the "did malloc fail?" check. Fix this by moving to the
glib alloc/free routines for this memory so we can use g_try_malloc0
rather than having a separate memset(). Spotted by Coverity (see
bug 887883).

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
We could obviously also fix this by just moving the memset after the
null check, but I think we want to move towards consistently using
the glib memory routines everywhere anyway.

 linux-user/elfload.c   |    5 ++---
 linux-user/linuxload.c |    2 +-
 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index a413976..4635bb2 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -1105,8 +1105,7 @@ static abi_ulong copy_elf_strings(int argc,char ** argv, void **page,
                 offset = p % TARGET_PAGE_SIZE;
                 pag = (char *)page[p/TARGET_PAGE_SIZE];
                 if (!pag) {
-                    pag = (char *)malloc(TARGET_PAGE_SIZE);
-                    memset(pag, 0, TARGET_PAGE_SIZE);
+                    pag = g_try_malloc0(TARGET_PAGE_SIZE);
                     page[p/TARGET_PAGE_SIZE] = pag;
                     if (!pag)
                         return 0;
@@ -1164,7 +1163,7 @@ static abi_ulong setup_arg_pages(abi_ulong p, struct linux_binprm *bprm,
             info->rss++;
             /* FIXME - check return value of memcpy_to_target() for failure */
             memcpy_to_target(stack_base, bprm->page[i], TARGET_PAGE_SIZE);
-            free(bprm->page[i]);
+            g_free(bprm->page[i]);
         }
         stack_base += TARGET_PAGE_SIZE;
     }
diff --git a/linux-user/linuxload.c b/linux-user/linuxload.c
index 62ebc7e..b47025f 100644
--- a/linux-user/linuxload.c
+++ b/linux-user/linuxload.c
@@ -178,7 +178,7 @@ int loader_exec(const char * filename, char ** argv, char ** envp,
 
     /* Something went wrong, return the inode and free the argument pages*/
     for (i=0 ; i<MAX_ARG_PAGES ; i++) {
-        free(bprm->page[i]);
+        g_free(bprm->page[i]);
     }
     return(retval);
 }
-- 
1.7.1

Re: [Qemu-devel] [PATCH] linux-user/elfload.c: Don't memset(NULL..) if malloc() failed

[Anthony Liguori]

On 11/09/2011 01:22 PM, Peter Maydell wrote:
> If a malloc() in copy_elf_strings() failed we would call memset()
> before the "did malloc fail?" check. Fix this by moving to the
> glib alloc/free routines for this memory so we can use g_try_malloc0
> rather than having a separate memset(). Spotted by Coverity (see
> bug 887883).
>
> Signed-off-by: Peter Maydell<peter.maydell@linaro.org>

Applied.  Thanks.

Regards,

Anthony Liguori

> ---
> We could obviously also fix this by just moving the memset after the
> null check, but I think we want to move towards consistently using
> the glib memory routines everywhere anyway.
>
>   linux-user/elfload.c   |    5 ++---
>   linux-user/linuxload.c |    2 +-
>   2 files changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
> index a413976..4635bb2 100644
> --- a/linux-user/elfload.c
> +++ b/linux-user/elfload.c
> @@ -1105,8 +1105,7 @@ static abi_ulong copy_elf_strings(int argc,char ** argv, void **page,
>                   offset = p % TARGET_PAGE_SIZE;
>                   pag = (char *)page[p/TARGET_PAGE_SIZE];
>                   if (!pag) {
> -                    pag = (char *)malloc(TARGET_PAGE_SIZE);
> -                    memset(pag, 0, TARGET_PAGE_SIZE);
> +                    pag = g_try_malloc0(TARGET_PAGE_SIZE);
>                       page[p/TARGET_PAGE_SIZE] = pag;
>                       if (!pag)
>                           return 0;
> @@ -1164,7 +1163,7 @@ static abi_ulong setup_arg_pages(abi_ulong p, struct linux_binprm *bprm,
>               info->rss++;
>               /* FIXME - check return value of memcpy_to_target() for failure */
>               memcpy_to_target(stack_base, bprm->page[i], TARGET_PAGE_SIZE);
> -            free(bprm->page[i]);
> +            g_free(bprm->page[i]);
>           }
>           stack_base += TARGET_PAGE_SIZE;
>       }
> diff --git a/linux-user/linuxload.c b/linux-user/linuxload.c
> index 62ebc7e..b47025f 100644
> --- a/linux-user/linuxload.c
> +++ b/linux-user/linuxload.c
> @@ -178,7 +178,7 @@ int loader_exec(const char * filename, char ** argv, char ** envp,
>
>       /* Something went wrong, return the inode and free the argument pages*/
>       for (i=0 ; i<MAX_ARG_PAGES ; i++) {
> -        free(bprm->page[i]);
> +        g_free(bprm->page[i]);
>       }
>       return(retval);
>   }