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); > -- Kees Cook
