On Thu, Nov 11, 2021 at 7:35 PM Petr Mladek <pmladek@xxxxxxxx> wrote: > > On Thu 2021-11-11 11:06:04, David Hildenbrand wrote: > > On 11.11.21 11:03, David Hildenbrand wrote: > > > On 08.11.21 09:38, Yafang Shao wrote: > > >> It is better to use get_task_comm() instead of the open coded string > > >> copy as we do in other places. > > >> > > >> struct elf_prpsinfo is used to dump the task information in userspace > > >> coredump or kernel vmcore. Below is the verfication of vmcore, > > >> > > >> crash> ps > > >> PID PPID CPU TASK ST %MEM VSZ RSS COMM > > >> 0 0 0 ffffffff9d21a940 RU 0.0 0 0 [swapper/0] > > >>> 0 0 1 ffffa09e40f85e80 RU 0.0 0 0 [swapper/1] > > >>> 0 0 2 ffffa09e40f81f80 RU 0.0 0 0 [swapper/2] > > >>> 0 0 3 ffffa09e40f83f00 RU 0.0 0 0 [swapper/3] > > >>> 0 0 4 ffffa09e40f80000 RU 0.0 0 0 [swapper/4] > > >>> 0 0 5 ffffa09e40f89f80 RU 0.0 0 0 [swapper/5] > > >> 0 0 6 ffffa09e40f8bf00 RU 0.0 0 0 [swapper/6] > > >>> 0 0 7 ffffa09e40f88000 RU 0.0 0 0 [swapper/7] > > >>> 0 0 8 ffffa09e40f8de80 RU 0.0 0 0 [swapper/8] > > >>> 0 0 9 ffffa09e40f95e80 RU 0.0 0 0 [swapper/9] > > >>> 0 0 10 ffffa09e40f91f80 RU 0.0 0 0 [swapper/10] > > >>> 0 0 11 ffffa09e40f93f00 RU 0.0 0 0 [swapper/11] > > >>> 0 0 12 ffffa09e40f90000 RU 0.0 0 0 [swapper/12] > > >>> 0 0 13 ffffa09e40f9bf00 RU 0.0 0 0 [swapper/13] > > >>> 0 0 14 ffffa09e40f98000 RU 0.0 0 0 [swapper/14] > > >>> 0 0 15 ffffa09e40f9de80 RU 0.0 0 0 [swapper/15] > > >> > > >> It works well as expected. > > >> > > >> Suggested-by: Kees Cook <keescook@xxxxxxxxxxxx> > > >> Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx> > > >> Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> > > >> Cc: Arnaldo Carvalho de Melo <arnaldo.melo@xxxxxxxxx> > > >> Cc: Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> > > >> Cc: Michal Miroslaw <mirq-linux@xxxxxxxxxxxx> > > >> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > > >> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> > > >> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> > > >> Cc: David Hildenbrand <david@xxxxxxxxxx> > > >> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> > > >> Cc: Kees Cook <keescook@xxxxxxxxxxxx> > > >> Cc: Petr Mladek <pmladek@xxxxxxxx> > > >> --- > > >> fs/binfmt_elf.c | 2 +- > > >> 1 file changed, 1 insertion(+), 1 deletion(-) > > >> > > >> diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c > > >> index a813b70f594e..138956fd4a88 100644 > > >> --- a/fs/binfmt_elf.c > > >> +++ b/fs/binfmt_elf.c > > >> @@ -1572,7 +1572,7 @@ static int fill_psinfo(struct elf_prpsinfo *psinfo, struct task_struct *p, > > >> SET_UID(psinfo->pr_uid, from_kuid_munged(cred->user_ns, cred->uid)); > > >> SET_GID(psinfo->pr_gid, from_kgid_munged(cred->user_ns, cred->gid)); > > >> rcu_read_unlock(); > > >> - strncpy(psinfo->pr_fname, p->comm, sizeof(psinfo->pr_fname)); > > >> + get_task_comm(psinfo->pr_fname, p); > > >> > > >> return 0; > > >> } > > >> > > > > > > We have a hard-coded "pr_fname[16]" as well, not sure if we want to > > > adjust that to use TASK_COMM_LEN? > > > > But if the intention is to chance TASK_COMM_LEN later, we might want to > > keep that unchanged. > > It seems that len will not change in the end. Another solution is > going to be used for the long names, see > https://lore.kernel.org/r/20211108084142.4692-1-laoar.shao@xxxxxxxxx. > > > (replacing the 16 by a define might still be a good idea, similar to how > > it's done for ELF_PRARGSZ, but just a thought) > > If the code would need some tweaking when the size changes, you could > still use TASK_COMM_LEN and trigger a compilation error when the size > gets modified. For example, static_assert(TASK_COMM_LEN == 16); > > It will make it clear that it needs attention if the size is ever modified. > I think we can just add some comments to make it grepable, for example, + /* TASK_COMM_LEN */ char pr_fname[16]; or a more detailed explanation: + /* + * The hard-coded 16 is derived from TASK_COMM_LEN, but it can be changed as + * it is exposed to userspace. We'd better make it hard-coded here. + */ char pr_fname[16]; -- Thanks Yafang
