On Mon, Oct 25, 2021 at 08:33:08AM +0000, Yafang Shao 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. > > Replacing strncpy() with strscpy_pad() can avoid this warning. > > This patch also replace the hard-coded 16 with TASK_COMM_LEN to make it > more compatible with task comm size change. > > I also verfied if it still work well when I extend the comm size to 24. > 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. > > Reported-by: kernel test robot <lkp@xxxxxxxxx> > 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: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> > Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> > Cc: Kees Cook <keescook@xxxxxxxxxxxx> > Cc: Petr Mladek <pmladek@xxxxxxxx> > --- > fs/binfmt_elf.c | 2 +- > include/linux/elfcore-compat.h | 3 ++- > include/linux/elfcore.h | 4 ++-- > 3 files changed, 5 insertions(+), 4 deletions(-) > > diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c > index a813b70f594e..a4ba79fce2a9 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)); > + strscpy_pad(psinfo->pr_fname, p->comm, sizeof(psinfo->pr_fname)); This should use get_task_comm(). > > return 0; > } > diff --git a/include/linux/elfcore-compat.h b/include/linux/elfcore-compat.h > index e272c3d452ce..afa0eb45196b 100644 > --- a/include/linux/elfcore-compat.h > +++ b/include/linux/elfcore-compat.h > @@ -5,6 +5,7 @@ > #include <linux/elf.h> > #include <linux/elfcore.h> > #include <linux/compat.h> > +#include <linux/sched.h> > > /* > * Make sure these layouts match the linux/elfcore.h native definitions. > @@ -43,7 +44,7 @@ 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..8d79cd58b09a 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 > These structs are externally parsed -- we can't change the size of pr_fname AFAICT. -- Kees Cook
