From: Kees Cook <keescook@chromium.org> To: Jeff Kirsher <jeffrey.t.kirsher@intel.com> Cc: Alexander Potapenko <glider@google.com>, Kees Cook <keescook@chromium.org>, intel-wired-lan@lists.osuosl.org, linux-kernel@vger.kernel.org Subject: [PATCH] e1000: Distribute switch variables for initialization Date: Wed, 19 Feb 2020 22:23:02 -0800 [thread overview] Message-ID: <20200220062302.68898-1-keescook@chromium.org> (raw) 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/net/ethernet/intel/e1000/e1000_main.c: In function ‘e1000_xmit_frame’: drivers/net/ethernet/intel/e1000/e1000_main.c:3143:18: warning: statement will never be executed [-Wswitch-unreachable] 3143 | unsigned int pull_size; | ^~~~~~~~~ [1] https://bugs.llvm.org/show_bug.cgi?id=44916 Signed-off-by: Kees Cook <keescook@chromium.org> --- drivers/net/ethernet/intel/e1000/e1000_main.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c b/drivers/net/ethernet/intel/e1000/e1000_main.c index 2bced34c19ba..a540d0206129 100644 --- a/drivers/net/ethernet/intel/e1000/e1000_main.c +++ b/drivers/net/ethernet/intel/e1000/e1000_main.c @@ -3140,8 +3140,9 @@ static netdev_tx_t e1000_xmit_frame(struct sk_buff *skb, hdr_len = skb_transport_offset(skb) + tcp_hdrlen(skb); if (skb->data_len && hdr_len == len) { switch (hw->mac_type) { + case e1000_82544: { unsigned int pull_size; - case e1000_82544: + /* Make sure we have room to chop off 4 bytes, * and that the end alignment will work out to * this hardware's requirements @@ -3162,6 +3163,7 @@ static netdev_tx_t e1000_xmit_frame(struct sk_buff *skb, } len = skb_headlen(skb); break; + } default: /* do nothing */ break;
WARNING: multiple messages have this Message-ID (diff)
From: Kees Cook <keescook@chromium.org> To: intel-wired-lan@osuosl.org Subject: [Intel-wired-lan] [PATCH] e1000: Distribute switch variables for initialization Date: Wed, 19 Feb 2020 22:23:02 -0800 [thread overview] Message-ID: <20200220062302.68898-1-keescook@chromium.org> (raw) 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/net/ethernet/intel/e1000/e1000_main.c: In function ?e1000_xmit_frame?: drivers/net/ethernet/intel/e1000/e1000_main.c:3143:18: warning: statement will never be executed [-Wswitch-unreachable] 3143 | unsigned int pull_size; | ^~~~~~~~~ [1] https://bugs.llvm.org/show_bug.cgi?id=44916 Signed-off-by: Kees Cook <keescook@chromium.org> --- drivers/net/ethernet/intel/e1000/e1000_main.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c b/drivers/net/ethernet/intel/e1000/e1000_main.c index 2bced34c19ba..a540d0206129 100644 --- a/drivers/net/ethernet/intel/e1000/e1000_main.c +++ b/drivers/net/ethernet/intel/e1000/e1000_main.c @@ -3140,8 +3140,9 @@ static netdev_tx_t e1000_xmit_frame(struct sk_buff *skb, hdr_len = skb_transport_offset(skb) + tcp_hdrlen(skb); if (skb->data_len && hdr_len == len) { switch (hw->mac_type) { + case e1000_82544: { unsigned int pull_size; - case e1000_82544: + /* Make sure we have room to chop off 4 bytes, * and that the end alignment will work out to * this hardware's requirements @@ -3162,6 +3163,7 @@ static netdev_tx_t e1000_xmit_frame(struct sk_buff *skb, } len = skb_headlen(skb); break; + } default: /* do nothing */ break;
next reply other threads:[~2020-02-20 6:23 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-02-20 6:23 Kees Cook [this message] 2020-02-20 6:23 ` [Intel-wired-lan] [PATCH] e1000: Distribute switch variables for initialization Kees Cook 2020-02-22 2:01 ` Brown, Aaron F 2020-02-22 2:01 ` Brown, Aaron F
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