On 09/14, Tetsuo Handa wrote:
>
> # echo '|' > /proc/sys/kernel/core_pattern
>
> and got
>
> BUG: unable to handle kernel NULL pointer dereference at (null)
Hmm. This was fixed by 264b83c07a8 "usermodehelper: check
subprocess_info->path != NULL".
But then this check was removed by 7f57cfa4e2a "usermodehelper:
kill the sub_info->path[0] check".
Note that the changelog says "do_execve(NULL) is safe" and I certainly
tested this case when I sent the patch...
Now it is crashes in path_openat() because pathname->name is NULL.
Something was changed, perhaps or (I'm afraid) I misread that code and
my testing was wrong. do_filp_open/etc were changed to accept
"struct filename *" a long ago.
> upon core dump because helper_argv[0] == NULL at
>
> helper_argv = argv_split(GFP_KERNEL, cn.corename, NULL);
> call_usermodehelper_setup(helper_argv[0], ...);
Are you sure? See above.
> --- a/lib/argv_split.c
> +++ b/lib/argv_split.c
> @@ -50,7 +50,7 @@ EXPORT_SYMBOL(argv_free);
> * quote processing is performed. Multiple whitespace characters are
> * considered to be a single argument separator. The returned array
> * is always NULL-terminated. Returns NULL on memory allocation
> - * failure.
> + * failure or @str being empty or @str containing only white-space.
> *
> * The source string at `str' may be undergoing concurrent alteration via
> * userspace sysctl activity (at least). The argv_split() implementation
> @@ -68,6 +68,10 @@ char **argv_split(gfp_t gfp, const char *str, int *argcp)
> return NULL;
>
> argc = count_argc(argv_str);
> + if (!argc) {
> + kfree(argv_str);
> + return NULL;
> + }
Yes, this is what 264b83c07a8 suggested... But I am not sure, if nothing
else pr_warn("failed to allocate memory") from do_coredump() doesn't look
nice in this case.
Perhaps
--- x/kernel/kmod.c
+++ x/kernel/kmod.c
@@ -571,6 +571,9 @@ int call_usermodehelper_exec(struct subp
DECLARE_COMPLETION_ONSTACK(done);
int retval = 0;
+ if (!sub_info->path)
+ return -EXXX;
+
helper_lock();
if (!khelper_wq || usermodehelper_disabled) {
retval = -EBUSY;
?
Oleg.
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