On Sat, Aug 10, 2024 at 09:30:25PM -0400, Waiman Long wrote:
On 8/10/24 00:05, Herbert Xu wrote:Unless I'm missing something chunk_size cannot be zero before the
Waiman Long <longman@xxxxxxxxxx> wrote:I think DIV_ROUND_UP() will exactly the same problem that if chunk_size is
diff --git a/kernel/padata.c b/kernel/padata.cPerhaps change the first ps.chunk_size assignment to use DIV_ROUND_UP
index 53f4bc912712..0fa6c2895460 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -517,6 +517,13 @@ void __init padata_do_multithreaded(struct padata_mt_job *job)
ps.chunk_size = max(ps.chunk_size, job->min_chunk);
ps.chunk_size = roundup(ps.chunk_size, job->align);
+ /*
+ * chunk_size can be 0 if the caller sets min_chunk to 0. So force it
+ * to at least 1 to prevent divide-by-0 panic in padata_mt_helper().`
+ */
+ if (!ps.chunk_size)
+ ps.chunk_size = 1U;
instead?
0, you still got a 0 result. round_up() only if the 2nd argument is a power
of 2 while with DIV_ROUND_UP(), the second argument can be any number except
0.
division because that's the first thing we check upon entry into
this function.