On Tue, Mar 03, 2020 at 10:55:22AM -0500, Jeff Layton wrote: > On Mon, 2020-03-02 at 20:41 -0800, Kees Cook wrote: > > On Wed, Feb 19, 2020 at 10:22:43PM -0800, Kees Cook wrote: > > > Variables declared in a switch statement before any case statements > > > cannot be automatically initialized with compiler instrumentation (as > > > they are not part of any execution flow). With GCC's proposed automatic > > > stack variable initialization feature, this triggers a warning (and they > > > don't get initialized). Clang's automatic stack variable initialization > > > (via CONFIG_INIT_STACK_ALL=y) doesn't throw a warning, but it also > > > doesn't initialize such variables[1]. Note that these warnings (or silent > > > skipping) happen before the dead-store elimination optimization phase, > > > so even when the automatic initializations are later elided in favor of > > > direct initializations, the warnings remain. > > > > > > To avoid these problems, move such variables into the "case" where > > > they're used or lift them up into the main function body. > > > > > > fs/fcntl.c: In function ‘send_sigio_to_task’: > > > fs/fcntl.c:738:20: warning: statement will never be executed [-Wswitch-unreachable] > > > 738 | kernel_siginfo_t si; > > > | ^~ > > > > > > [1] https://bugs.llvm.org/show_bug.cgi?id=44916 > > > > > > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> > > > > Ping. Can someone pick this up, please? > > > > Thanks! > > > > -Kees > > > > > --- > > > fs/fcntl.c | 6 ++++-- > > > 1 file changed, 4 insertions(+), 2 deletions(-) > > > > > > diff --git a/fs/fcntl.c b/fs/fcntl.c > > > index 9bc167562ee8..2e4c0fa2074b 100644 > > > --- a/fs/fcntl.c > > > +++ b/fs/fcntl.c > > > @@ -735,8 +735,9 @@ static void send_sigio_to_task(struct task_struct *p, > > > return; > > > > > > switch (signum) { > > > - kernel_siginfo_t si; > > > - default: > > > + default: { > > > + kernel_siginfo_t si; > > > + > > > /* Queue a rt signal with the appropriate fd as its > > > value. We use SI_SIGIO as the source, not > > > SI_KERNEL, since kernel signals always get > > > @@ -769,6 +770,7 @@ static void send_sigio_to_task(struct task_struct *p, > > > si.si_fd = fd; > > > if (!do_send_sig_info(signum, &si, p, type)) > > > break; > > > + } > > > /* fall-through - fall back on the old plain SIGIO signal */ > > > case 0: > > > do_send_sig_info(SIGIO, SEND_SIG_PRIV, p, type); > > > > > Sure, looks straightforward enough. I'll pick it up for v5.7. Awesome; thank you! -Kees > > Thanks, > -- > Jeff Layton <jlayton@xxxxxxxxxx> > -- Kees Cook
