From: Yafang Shao <laoar.shao@xxxxxxxxx>
Subject: fs/binfmt_elf: replace open-coded string copy with get_task_comm
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 verification 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.
Some comments are added to explain why we use the hard-coded 16.
Link: https://lkml.kernel.org/r/20211120112738.45980-5-laoar.shao@xxxxxxxxx
Suggested-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
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>
Cc: Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx>
Cc: Andrii Nakryiko <andrii@xxxxxxxxxx>
Cc: Dennis Dalessandro <dennis.dalessandro@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/binfmt_elf.c | 2 +-
include/linux/elfcore-compat.h | 5 +++++
include/linux/elfcore.h | 5 +++++
3 files changed, 11 insertions(+), 1 deletion(-)
--- a/fs/binfmt_elf.c~fs-binfmt_elf-replace-open-coded-string-copy-with-get_task_comm
+++ a/fs/binfmt_elf.c
@@ -1585,7 +1585,7 @@ static int fill_psinfo(struct elf_prpsin
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;
}
--- a/include/linux/elfcore-compat.h~fs-binfmt_elf-replace-open-coded-string-copy-with-get_task_comm
+++ a/include/linux/elfcore-compat.h
@@ -43,6 +43,11 @@ 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;
+ /*
+ * The hard-coded 16 is derived from TASK_COMM_LEN, but it can't be
+ * changed as it is exposed to userspace. We'd better make it hard-coded
+ * here.
+ */
char pr_fname[16];
char pr_psargs[ELF_PRARGSZ];
};
--- a/include/linux/elfcore.h~fs-binfmt_elf-replace-open-coded-string-copy-with-get_task_comm
+++ a/include/linux/elfcore.h
@@ -65,6 +65,11 @@ struct elf_prpsinfo
__kernel_gid_t pr_gid;
pid_t pr_pid, pr_ppid, pr_pgrp, pr_sid;
/* Lots missing */
+ /*
+ * The hard-coded 16 is derived from TASK_COMM_LEN, but it can't be
+ * changed as it is exposed to userspace. We'd better make it hard-coded
+ * here.
+ */
char pr_fname[16]; /* filename of executable */
char pr_psargs[ELF_PRARGSZ]; /* initial part of arg list */
};
_
