Re: [PATCH v2 06/10] mm/kmemleak: Replace strncpy() with __get_task_comm()
From: Catalin Marinas <catalin.marinas@arm.com>
Date: 2024-06-13 08:37:20
Also in:
bpf, dri-devel, linux-fsdevel, linux-mm, linux-trace-kernel, netdev, selinux
On Thu, Jun 13, 2024 at 10:30:40AM +0800, Yafang Shao wrote:
quoted hunk ↗ jump to hunk
Using __get_task_comm() to read the task comm ensures that the name is always NUL-terminated, regardless of the source string. This approach also facilitates future extensions to the task comm. Signed-off-by: Yafang Shao <redacted> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Andrew Morton <akpm@linux-foundation.org> --- mm/kmemleak.c | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-)diff --git a/mm/kmemleak.c b/mm/kmemleak.c index d5b6fba44fc9..ef29aaab88a0 100644 --- a/mm/kmemleak.c +++ b/mm/kmemleak.c@@ -663,13 +663,7 @@ static struct kmemleak_object *__alloc_object(gfp_t gfp) strncpy(object->comm, "softirq", sizeof(object->comm)); } else { object->pid = current->pid; - /* - * There is a small chance of a race with set_task_comm(), - * however using get_task_comm() here may cause locking - * dependency issues with current->alloc_lock. In the worst - * case, the command line is not correct. - */ - strncpy(object->comm, current->comm, sizeof(object->comm)); + __get_task_comm(object->comm, sizeof(object->comm), current); }
You deleted the comment stating why it does not use get_task_comm() without explaining why it would be safe now. I don't recall the details but most likely lockdep warned of some potential deadlocks with this function being called with the task_lock held. So, you either show why this is safe or just use strscpy() directly here (not sure we'd need strscpy_pad(); I think strscpy() would do, we just need the NUL-termination). -- Catalin