From: Kees Cook keescook@chromium.org
[ Upstream commit a34c7f5156654ebaf7eaace102938be7ff7036cb ]
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 Tested-by: Aaron Brown aaron.f.brown@intel.com Signed-off-by: Jeff Kirsher jeffrey.t.kirsher@intel.com Signed-off-by: Sasha Levin sashal@kernel.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 0d51cbc88028..05bc6e216bca 100644 --- a/drivers/net/ethernet/intel/e1000/e1000_main.c +++ b/drivers/net/ethernet/intel/e1000/e1000_main.c @@ -3136,8 +3136,9 @@ 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 @@ -3158,6 +3159,7 @@ static netdev_tx_t e1000_xmit_frame(struct sk_buff *skb, } len = skb_headlen(skb); break; + } default: /* do nothing */ break;