| Message ID | 20211108083840.4627-2-laoar.shao@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | task comm cleanups | expand |
On 08.11.21 09:38, Yafang Shao wrote: > Make sure the string set to task comm is always nul terminated. > strlcpy: "the result is always a valid NUL-terminated string that fits in the buffer" The only difference seems to be that strscpy_pad() pads the remainder with zeroes. Is this description correct and I am missing something important? > Signed-off-by: Yafang Shao <laoar.shao@gmail.com> > Reviewed-by: Kees Cook <keescook@chromium.org> > Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> > Cc: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com> > Cc: Alexei Starovoitov <alexei.starovoitov@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/exec.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/exec.c b/fs/exec.c > index a098c133d8d7..404156b5b314 100644 > --- a/fs/exec.c > +++ b/fs/exec.c > @@ -1224,7 +1224,7 @@ void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec) > { > task_lock(tsk); > trace_task_rename(tsk, buf); > - strlcpy(tsk->comm, buf, sizeof(tsk->comm)); > + strscpy_pad(tsk->comm, buf, sizeof(tsk->comm)); > task_unlock(tsk); > perf_event_comm(tsk, exec); > } >
On Wed, Nov 10, 2021 at 4:28 PM David Hildenbrand <david@redhat.com> wrote: > > On 08.11.21 09:38, Yafang Shao wrote: > > Make sure the string set to task comm is always nul terminated. > > > > strlcpy: "the result is always a valid NUL-terminated string that fits > in the buffer" > > The only difference seems to be that strscpy_pad() pads the remainder > with zeroes. > > Is this description correct and I am missing something important? > In a earlier version [1], the checkpatch.py found a warning: WARNING: Prefer strscpy over strlcpy - see: https://lore.kernel.org/r/CAHk-=wgfRnXz0W3D37d01q3JFkr_i_uTL=V6A6G1oUZcprmknw@mail.gmail.com/ So I replaced strlcpy() with strscpy() to fix this warning. And then in v5[2], the strscpy() was replaced with strscpy_pad() to make sure there's no garbade data and also make get_task_comm() be consistent with get_task_comm(). This commit log didn't clearly describe the historical changes. So I think we can update the commit log and subject with: Subject: use strscpy_pad with strlcpy in __set_task_comm Commit log: strlcpy is not suggested to use by the checkpatch.pl, so we'd better recplace it with strscpy. To avoid leaving garbage data and be consistent with the usage in __get_task_comm(), the strscpy_pad is used here. WDYT? [1]. https://lore.kernel.org/lkml/20211007120752.5195-3-laoar.shao@gmail.com/ [2]. https://lore.kernel.org/lkml/20211021034516.4400-2-laoar.shao@gmail.com/ > > Signed-off-by: Yafang Shao <laoar.shao@gmail.com> > > Reviewed-by: Kees Cook <keescook@chromium.org> > > Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> > > Cc: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com> > > Cc: Alexei Starovoitov <alexei.starovoitov@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/exec.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/fs/exec.c b/fs/exec.c > > index a098c133d8d7..404156b5b314 100644 > > --- a/fs/exec.c > > +++ b/fs/exec.c > > @@ -1224,7 +1224,7 @@ void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec) > > { > > task_lock(tsk); > > trace_task_rename(tsk, buf); > > - strlcpy(tsk->comm, buf, sizeof(tsk->comm)); > > + strscpy_pad(tsk->comm, buf, sizeof(tsk->comm)); > > task_unlock(tsk); > > perf_event_comm(tsk, exec); > > } > > > > > -- > Thanks, > > David / dhildenb >
On Wed, Nov 10, 2021 at 09:28:12AM +0100, David Hildenbrand wrote: > On 08.11.21 09:38, Yafang Shao wrote: > > Make sure the string set to task comm is always nul terminated. > > > > strlcpy: "the result is always a valid NUL-terminated string that fits > in the buffer" > > The only difference seems to be that strscpy_pad() pads the remainder > with zeroes. > > Is this description correct and I am missing something important? Yes, this makes sure it's zero padded just to be robust against full tsk->comm copies that got noticed in other places. The only other change is that we want to remove strlcpy() from the kernel generally since it can trigger out-of-bound reads on the source string[1]. So, in this case, the most robust version is to use strscpy_pad(). -Kees [1] https://github.com/KSPP/linux/issues/89 > > > Signed-off-by: Yafang Shao <laoar.shao@gmail.com> > > Reviewed-by: Kees Cook <keescook@chromium.org> > > Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> > > Cc: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com> > > Cc: Alexei Starovoitov <alexei.starovoitov@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/exec.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/fs/exec.c b/fs/exec.c > > index a098c133d8d7..404156b5b314 100644 > > --- a/fs/exec.c > > +++ b/fs/exec.c > > @@ -1224,7 +1224,7 @@ void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec) > > { > > task_lock(tsk); > > trace_task_rename(tsk, buf); > > - strlcpy(tsk->comm, buf, sizeof(tsk->comm)); > > + strscpy_pad(tsk->comm, buf, sizeof(tsk->comm)); > > task_unlock(tsk); > > perf_event_comm(tsk, exec); > > } > > > > > -- > Thanks, > > David / dhildenb >
On 10.11.21 10:05, Yafang Shao wrote: > On Wed, Nov 10, 2021 at 4:28 PM David Hildenbrand <david@redhat.com> wrote: >> >> On 08.11.21 09:38, Yafang Shao wrote: >>> Make sure the string set to task comm is always nul terminated. >>> >> >> strlcpy: "the result is always a valid NUL-terminated string that fits >> in the buffer" >> >> The only difference seems to be that strscpy_pad() pads the remainder >> with zeroes. >> >> Is this description correct and I am missing something important? >> > > In a earlier version [1], the checkpatch.py found a warning: > WARNING: Prefer strscpy over strlcpy - see: > https://lore.kernel.org/r/CAHk-=wgfRnXz0W3D37d01q3JFkr_i_uTL=V6A6G1oUZcprmknw@mail.gmail.com/ > So I replaced strlcpy() with strscpy() to fix this warning. > And then in v5[2], the strscpy() was replaced with strscpy_pad() to > make sure there's no garbade data and also make get_task_comm() be > consistent with get_task_comm(). > > This commit log didn't clearly describe the historical changes. So I > think we can update the commit log and subject with: > > Subject: use strscpy_pad with strlcpy in __set_task_comm > Commit log: > strlcpy is not suggested to use by the checkpatch.pl, so we'd better > recplace it with strscpy. > To avoid leaving garbage data and be consistent with the usage in > __get_task_comm(), the strscpy_pad is used here. > > WDYT? Yes, that makes it clearer what this patch actually does :) With the subject+description changed Reviewed-by: David Hildenbrand <david@redhat.com> Thanks!
diff --git a/fs/exec.c b/fs/exec.c index a098c133d8d7..404156b5b314 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1224,7 +1224,7 @@ void __set_task_comm(struct task_struct *tsk, const char *buf, bool exec) { task_lock(tsk); trace_task_rename(tsk, buf); - strlcpy(tsk->comm, buf, sizeof(tsk->comm)); + strscpy_pad(tsk->comm, buf, sizeof(tsk->comm)); task_unlock(tsk); perf_event_comm(tsk, exec); }