| Message ID | 20211025083315.4752-3-laoar.shao@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | extend task comm from 16 to 24 | expand |
On Mon, Oct 25, 2021 at 08:33:05AM +0000, Yafang Shao wrote: > If the dest buffer size is smaller than sizeof(tsk->comm), the buffer > will be without null ternimator, that may cause problem. We can make sure > the buffer size not smaller than comm at the callsite to avoid that > problem, but there may be callsite that we can't easily change. > > Using strscpy_pad() instead of strncpy() in __get_task_comm() can make > the string always nul ternimated. > > Suggested-by: Kees Cook <keescook@chromium.org> > Suggested-by: Steven Rostedt <rostedt@goodmis.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: Peter Zijlstra <peterz@infradead.org> > Cc: Steven Rostedt <rostedt@goodmis.org> > Cc: Al Viro <viro@zeniv.linux.org.uk> > Cc: Kees Cook <keescook@chromium.org> > Cc: Petr Mladek <pmladek@suse.com> > --- > fs/exec.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/fs/exec.c b/fs/exec.c > index 404156b5b314..bf2a7a91eeea 100644 > --- a/fs/exec.c > +++ b/fs/exec.c > @@ -1209,7 +1209,8 @@ static int unshare_sighand(struct task_struct *me) > char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk) > { > task_lock(tsk); > - strncpy(buf, tsk->comm, buf_size); > + /* The copied value is always null terminated */ This may could say "always NUL terminated and zero-padded" > + strscpy_pad(buf, tsk->comm, buf_size); > task_unlock(tsk); > return buf; > } > -- > 2.17.1 > But for the replacement with strscpy_pad(), yes please: Reviewed-by: Kees Cook <keescook@chromium.org>
On Tue, Oct 26, 2021 at 5:08 AM Kees Cook <keescook@chromium.org> wrote: > > On Mon, Oct 25, 2021 at 08:33:05AM +0000, Yafang Shao wrote: > > If the dest buffer size is smaller than sizeof(tsk->comm), the buffer > > will be without null ternimator, that may cause problem. We can make sure > > the buffer size not smaller than comm at the callsite to avoid that > > problem, but there may be callsite that we can't easily change. > > > > Using strscpy_pad() instead of strncpy() in __get_task_comm() can make > > the string always nul ternimated. > > > > Suggested-by: Kees Cook <keescook@chromium.org> > > Suggested-by: Steven Rostedt <rostedt@goodmis.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: Peter Zijlstra <peterz@infradead.org> > > Cc: Steven Rostedt <rostedt@goodmis.org> > > Cc: Al Viro <viro@zeniv.linux.org.uk> > > Cc: Kees Cook <keescook@chromium.org> > > Cc: Petr Mladek <pmladek@suse.com> > > --- > > fs/exec.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/fs/exec.c b/fs/exec.c > > index 404156b5b314..bf2a7a91eeea 100644 > > --- a/fs/exec.c > > +++ b/fs/exec.c > > @@ -1209,7 +1209,8 @@ static int unshare_sighand(struct task_struct *me) > > char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk) > > { > > task_lock(tsk); > > - strncpy(buf, tsk->comm, buf_size); > > + /* The copied value is always null terminated */ > > This may could say "always NUL terminated and zero-padded" > Sure. I will change it. > > + strscpy_pad(buf, tsk->comm, buf_size); > > task_unlock(tsk); > > return buf; > > } > > -- > > 2.17.1 > > > > But for the replacement with strscpy_pad(), yes please: > > Reviewed-by: Kees Cook <keescook@chromium.org> > > > -- > Kees Cook
diff --git a/fs/exec.c b/fs/exec.c index 404156b5b314..bf2a7a91eeea 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1209,7 +1209,8 @@ static int unshare_sighand(struct task_struct *me) char *__get_task_comm(char *buf, size_t buf_size, struct task_struct *tsk) { task_lock(tsk); - strncpy(buf, tsk->comm, buf_size); + /* The copied value is always null terminated */ + strscpy_pad(buf, tsk->comm, buf_size); task_unlock(tsk); return buf; }
If the dest buffer size is smaller than sizeof(tsk->comm), the buffer will be without null ternimator, that may cause problem. We can make sure the buffer size not smaller than comm at the callsite to avoid that problem, but there may be callsite that we can't easily change. Using strscpy_pad() instead of strncpy() in __get_task_comm() can make the string always nul ternimated. Suggested-by: Kees Cook <keescook@chromium.org> Suggested-by: Steven Rostedt <rostedt@goodmis.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: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Kees Cook <keescook@chromium.org> Cc: Petr Mladek <pmladek@suse.com> --- fs/exec.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)