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From:   Yafang Shao <laoar.shao@gmail.com>
To:     akpm@linux-foundation.org
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        Kees Cook <keescook@chromium.org>,
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        Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>,
        Andrii Nakryiko <andrii.nakryiko@gmail.com>,
        Michal Miroslaw <mirq-linux@rere.qmqm.pl>,
        Peter Zijlstra <peterz@infradead.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Matthew Wilcox <willy@infradead.org>,
        David Hildenbrand <david@redhat.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Petr Mladek <pmladek@suse.com>
Subject: [PATCH 4/7] fs/binfmt_elf: use get_task_comm instead of open-coded string copy
Date:   Mon,  8 Nov 2021 08:38:37 +0000
Message-Id: <20211108083840.4627-5-laoar.shao@gmail.com>
In-Reply-To: <20211108083840.4627-1-laoar.shao@gmail.com>
References: <20211108083840.4627-1-laoar.shao@gmail.com>
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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@chromium.org>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Michal Miroslaw <mirq-linux@rere.qmqm.pl>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Kees Cook <keescook@chromium.org>
Cc: Petr Mladek <pmladek@suse.com>
---
 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;
 }
-- 
2.17.1