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Subject[PATCH v4 1/5] elfcore: use TASK_COMM_LEN instead of 16 in prpsinfo
Date
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@intel.com>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Petr Mladek <pmladek@suse.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];
};

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 */
};

static inline void elf_core_copy_regs(elf_gregset_t *elfregs, struct pt_regs *regs)
--
2.17.1

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