Fix segfault in maybe_script_execute.
Commit Message
Hi,
If glibc is built with gcc 8 and -march=z900,
the testcase posix/tst-spawn4-compat crashes with a segfault.
In function maybe_script_execute, the new_argv array is dynamically
initialized on stack with (argc + 1) elements.
The function wants to add _PATH_BSHELL as the first argument.
But if argc == 1, it writes three instead of two elements:
new_argv[0] = (char *) _PATH_BSHELL;
new_argv[1] = (char *) args->file;
new_argv[2] = NULL;
The latter write access writes to the same location where the
pointer args is stored on stack. Then it segfaults while accessing args:
args->exec (new_argv[0], new_argv, args->envp);
If argc > 1, the arguments inclusive the NULL termination of new_argv
is copied from argv with memcpy.
The implementation assumes that argc == 0 will never happen!
Okay to commit?
Bye
Stefan
---
ChangeLog:
* sysdeps/unix/sysv/linux/spawni.c (maybe_script_execute):
Increment size of new_argv by one.
Comments
On Sep 05 2018, Stefan Liebler <stli@linux.ibm.com> wrote:
> If argc > 1, the arguments inclusive the NULL termination of new_argv
> is copied from argv with memcpy.
But it has the same bug, doesn't it?
Andreas.
On 09/05/2018 03:44 PM, Andreas Schwab wrote:
> On Sep 05 2018, Stefan Liebler <stli@linux.ibm.com> wrote:
>
>> If argc > 1, the arguments inclusive the NULL termination of new_argv
>> is copied from argv with memcpy.
>
> But it has the same bug, doesn't it?
>
> Andreas.
>
Yes. It also has this bug.
Stefan
On Sep 06 2018, Stefan Liebler <stli@linux.ibm.com> wrote:
> On 09/05/2018 03:44 PM, Andreas Schwab wrote:
>> On Sep 05 2018, Stefan Liebler <stli@linux.ibm.com> wrote:
>>
>>> If argc > 1, the arguments inclusive the NULL termination of new_argv
>>> is copied from argv with memcpy.
>>
>> But it has the same bug, doesn't it?
>>
>> Andreas.
>>
> Yes. It also has this bug.
This makes the description rather confusing, implying there is a
difference between argc == 1 and argc > 1, which isn't.
Andreas.
commit d099212b378f23fef38ee3f51168bb247d5f719d
Author: Stefan Liebler <stli@linux.ibm.com>
Date: Wed Sep 5 13:34:44 2018 +0200
Fix segfault in maybe_script_execute.
If glibc is built with gcc 8 and -march=z900,
the testcase posix/tst-spawn4-compat crashes with a segfault.
In function maybe_script_execute, the new_argv array is dynamically
initialized on stack with (argc + 1) elements.
The function wants to add _PATH_BSHELL as the first argument.
But if argc == 1, it writes three instead of two elements:
new_argv[0] = (char *) _PATH_BSHELL;
new_argv[1] = (char *) args->file;
new_argv[2] = NULL;
The latter write access writes to the same location where the
pointer args is stored on stack. Then it segfaults while accessing args:
args->exec (new_argv[0], new_argv, args->envp);
If argc > 1, the arguments inclusive the NULL termination of new_argv
is copied from argv with memcpy.
The implementation assumes that argc == 0 will never happen!
ChangeLog:
* sysdeps/unix/sysv/linux/spawni.c (maybe_script_execute):
Increment size of new_argv by one.
@@ -101,7 +101,7 @@ maybe_script_execute (struct posix_spawn_args *args)
ptrdiff_t argc = args->argc;
/* Construct an argument list for the shell. */
- char *new_argv[argc + 1];
+ char *new_argv[argc + 2];
new_argv[0] = (char *) _PATH_BSHELL;
new_argv[1] = (char *) args->file;
if (argc > 1)