From e24cd4e6d6aa3ca741cdfdfc01118c4016acebea Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Wed, 19 Feb 2020 22:23:13 -0800 Subject: [PATCH] n_tty: Distribute switch variables for initialization MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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. drivers/tty/n_tty.c: In function ‘__process_echoes’: drivers/tty/n_tty.c:657:18: warning: statement will never be executed [-Wswitch-unreachable] 657 | unsigned int num_chars, num_bs; | ^~~~~~~~~ [1] https://bugs.llvm.org/show_bug.cgi?id=44916 Reviewed-by: Jiri Slaby Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20200220062313.69209-1-keescook@chromium.org Signed-off-by: Greg Kroah-Hartman --- drivers/tty/n_tty.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index 640fdd1e4c1d..1794d84e7bf6 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -654,9 +654,9 @@ static size_t __process_echoes(struct tty_struct *tty) op = echo_buf(ldata, tail + 1); switch (op) { + case ECHO_OP_ERASE_TAB: { unsigned int num_chars, num_bs; - case ECHO_OP_ERASE_TAB: if (MASK(ldata->echo_commit) == MASK(tail + 2)) goto not_yet_stored; num_chars = echo_buf(ldata, tail + 2); @@ -687,7 +687,7 @@ static size_t __process_echoes(struct tty_struct *tty) } tail += 3; break; - + } case ECHO_OP_SET_CANON_COL: ldata->canon_column = ldata->column; tail += 2;