Messages in this thread Patch in this message | | | Date | Mon, 21 Sep 2009 23:23:35 +0900 | From | Tejun Heo <> | Subject | Re: [PATCH] fix error handling in load_module() |
| |
Hello, Rusty.
Rusty Russell wrote: >> My reverse engineering of the secret, undocumented percpu_modfree() >> indicates that its mad inventor intended that percpu_modfree(NULL) be a >> valid thing to do. > > Yes, percpu_modfree() should handle NULL. If it doesn't, that's the bug.
Hmm... It seems the report was against pre-2.6.32-rcX window. ppc is still using the original percpu_modfree() and I don't think the it ever supported NULL free. In the current linus tree, the triggering BUG() would be at line 500 which is inside percpu_modfree() which checks @freeme matches any allocated address and if not triggers BUG().
I think something like the following should fix it.
kernel/module.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/kernel/module.c b/kernel/module.c index 05ce49c..eed1f9e 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -490,6 +490,9 @@ static void percpu_modfree(void *freeme) void *ptr = __per_cpu_start + block_size(pcpu_size[0]); int cpu;
+ if (unlikely(!freeme)) + return; + /* First entry is core kernel percpu data. */ for (i = 1; i < pcpu_num_used; ptr += block_size(pcpu_size[i]), i++) { if (ptr == freeme) { -- tejun
| |