On Thu, May 22, 2025 at 2:15 PM Yafang Shao <laoar.s...@gmail.com> wrote: > > On Wed, May 21, 2025 at 2:24 PM Bhupesh <bhup...@igalia.com> wrote: > > > > As Linus mentioned in [1], currently we have several memcpy() use-cases > > which use 'current->comm' to copy the task name over to local copies. > > For an example: > > > > ... > > char comm[TASK_COMM_LEN]; > > memcpy(comm, current->comm, TASK_COMM_LEN); > > ... > > > > These should be modified so that we can later implement approaches > > to handle the task->comm's 16-byte length limitation (TASK_COMM_LEN) > > is a more modular way (follow-up patches do the same): > > > > ... > > char comm[TASK_COMM_LEN]; > > memcpy(comm, current->comm, TASK_COMM_LEN); > > comm[TASK_COMM_LEN - 1] = '\0'; > > ... > > > > The relevant 'memcpy()' users were identified using the following search > > pattern: > > $ git grep 'memcpy.*->comm\>' > > Hello Bhupesh, > > Several BPF programs currently read task->comm directly, as seen in: > > // tools/testing/selftests/bpf/progs/test_skb_helpers.c [0] > bpf_probe_read_kernel_str(&comm, sizeof(comm), &task->comm); > > This approach may cause issues after the follow-up patch. > I believe we should replace it with the safer bpf_get_current_comm() > or explicitly null-terminate it with "comm[sizeof(comm) - 1] = '\0'". > Out-of-tree BPF programs like BCC[1] or bpftrace[2] relying on direct > task->comm access may also break and require updates. > > [0]. > https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/tree/tools/testing/selftests/bpf/progs/test_skb_helpers.c#n26 > [1]. https://github.com/iovisor/bcc > [2]. https://github.com/bpftrace/bpftrace
Hmm, upon checking, I confirmed that bpf_probe_read_kernel_str() already ensures the destination string is null-terminated. Therefore, this change is unnecessary. Please disregard my previous comment. -- Regards Yafang
