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Message-ID: <CALOAHbDn8xzm79R8_YJ+MF3SpKDKbouNCG21XYA0gsEO9xYNbw@mail.gmail.com>
Date: Thu, 14 Oct 2021 09:46:21 +0800
From: Yafang Shao <laoar.shao@...il.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Kees Cook <keescook@...omium.org>,
Peter Zijlstra <peterz@...radead.org>,
Petr Mladek <pmladek@...e.com>,
Al Viro <viro@...iv.linux.org.uk>,
Andrew Morton <akpm@...ux-foundation.org>,
Valentin Schneider <valentin.schneider@....com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
qiang.zhang@...driver.com, robdclark@...omium.org,
christian@...uner.io, Dietmar Eggemann <dietmar.eggemann@....com>,
Ingo Molnar <mingo@...hat.com>,
Juri Lelli <juri.lelli@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
Benjamin Segall <bsegall@...gle.com>,
Mel Gorman <mgorman@...e.de>,
Daniel Bristot de Oliveira <bristot@...hat.com>,
David Miller <davem@...emloft.net>, kuba@...nel.org,
LKML <linux-kernel@...r.kernel.org>,
kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v4 1/5] elfcore: use TASK_COMM_LEN instead of 16 in prpsinfo
On Wed, Oct 13, 2021 at 9:11 PM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Wed, 13 Oct 2021 10:23:42 +0000
> Yafang Shao <laoar.shao@...il.com> wrote:
>
> > kernel test robot reported a -Wstringop-truncation warning after I
> > extend task comm from 16 to 24. Below is the detailed warning:
> >
> > fs/binfmt_elf.c: In function 'fill_psinfo.isra':
> > >> fs/binfmt_elf.c:1575:9: warning: 'strncpy' output may be truncated copying 16 bytes from a string of length 23 [-Wstringop-truncation]
> > 1575 | strncpy(psinfo->pr_fname, p->comm, sizeof(psinfo->pr_fname));
> > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > This patch can fix this warning.
> >
> > struct elf_prpsinfo was moved from include/uapi/linux/elfcore.h into
> > include/linux/elfcore.h in commit
> > 1e6b57d6421f ("unexport linux/elfcore.h")
> >
> > As it is not UAPI code, we can replace 16 with TASK_COMM_LEN without
> > worrying about breaking userspace things.
> >
> > struct elf_prpsinfo is used to dump the task information in userspace
> > coredump or kernel vmcore. So I verified what will happen to vmcore if
> > I extend the size of TASK_COMM_LEN to 24. The result is that the vmcore
> > still work fine as expected, for example:
> >
> > crash> ps
> > PID PPID CPU TASK ST %MEM VSZ RSS COMM
> > > 0 0 0 ffffffff8501a940 RU 0.0 0 0 [swapper/0]
> > > 0 0 1 ffff996e00f81f80 RU 0.0 0 0 [swapper/1]
> > > 0 0 2 ffff996e00f80000 RU 0.0 0 0 [swapper/2]
> > > 0 0 3 ffff996e00f85e80 RU 0.0 0 0 [swapper/3]
> > > 0 0 4 ffff996e00f83f00 RU 0.0 0 0 [swapper/4]
> > 0 0 5 ffff996e00f8de80 RU 0.0 0 0 [swapper/5]
> > > 0 0 6 ffff996e00f8bf00 RU 0.0 0 0 [swapper/6]
> > > 0 0 7 ffff996e00f89f80 RU 0.0 0 0 [swapper/7]
> > > 0 0 8 ffff996e00f88000 RU 0.0 0 0 [swapper/8]
> > > 0 0 9 ffff996e00f93f00 RU 0.0 0 0 [swapper/9]
> > > 0 0 10 ffff996e00f91f80 RU 0.0 0 0 [swapper/10]
> > > 0 0 11 ffff996e00f90000 RU 0.0 0 0 [swapper/11]
> > > 0 0 12 ffff996e00f95e80 RU 0.0 0 0 [swapper/12]
> > > 0 0 13 ffff996e00f98000 RU 0.0 0 0 [swapper/13]
> > > 0 0 14 ffff996e00f9de80 RU 0.0 0 0 [swapper/14]
> > > 0 0 15 ffff996e00f9bf00 RU 0.0 0 0 [swapper/15]
> >
> > Reported-by: kernel test robot <lkp@...el.com>
> > Signed-off-by: Yafang Shao <laoar.shao@...il.com>
> > Cc: Peter Zijlstra <peterz@...radead.org>
> > Cc: Steven Rostedt <rostedt@...dmis.org>
> > Cc: Kees Cook <keescook@...omium.org>
> > Cc: Al Viro <viro@...iv.linux.org.uk>
> > Cc: Petr Mladek <pmladek@...e.com>
> > ---
> > include/linux/elfcore-compat.h | 2 +-
> > include/linux/elfcore.h | 4 ++--
> > 2 files changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/include/linux/elfcore-compat.h b/include/linux/elfcore-compat.h
> > index e272c3d452ce..8a52a782161d 100644
> > --- a/include/linux/elfcore-compat.h
> > +++ b/include/linux/elfcore-compat.h
> > @@ -43,7 +43,7 @@ struct compat_elf_prpsinfo
> > __compat_uid_t pr_uid;
> > __compat_gid_t pr_gid;
> > compat_pid_t pr_pid, pr_ppid, pr_pgrp, pr_sid;
> > - char pr_fname[16];
> > + char pr_fname[TASK_COMM_LEN];
> > char pr_psargs[ELF_PRARGSZ];
> > };
>
> Nice clean up, but should we add "#include <linux/sched.h>" to this header,
> to make sure that it pulls in TASK_COMM_LEN define and not just hope it
> gets pulled in beforehand by chance?
>
Sure, I will add it.
Thanks for the suggestion.
> >
> > diff --git a/include/linux/elfcore.h b/include/linux/elfcore.h
> > index 2aaa15779d50..ff4e4e455160 100644
> > --- a/include/linux/elfcore.h
> > +++ b/include/linux/elfcore.h
> > @@ -65,8 +65,8 @@ struct elf_prpsinfo
> > __kernel_gid_t pr_gid;
> > pid_t pr_pid, pr_ppid, pr_pgrp, pr_sid;
> > /* Lots missing */
> > - char pr_fname[16]; /* filename of executable */
> > - char pr_psargs[ELF_PRARGSZ]; /* initial part of arg list */
> > + char pr_fname[TASK_COMM_LEN]; /* filename of executable */
> > + char pr_psargs[ELF_PRARGSZ]; /* initial part of arg list */
>
> This header is fine, as it pulls in sched/task_stack.h which includes
> sched.h.
>
> -- Steve
>
> > };
> >
> > static inline void elf_core_copy_regs(elf_gregset_t *elfregs, struct pt_regs *regs)
>
--
Thanks
Yafang
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