linux-kernel - [PATCH] net/i40e: Replace 0-length array with flexible array

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Message-Id: <20230105234557.never.799-kees@kernel.org>
Date:   Thu,  5 Jan 2023 15:46:01 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Jesse Brandeburg <jesse.brandeburg@...el.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Tony Nguyen <anthony.l.nguyen@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH] net/i40e: Replace 0-length array with flexible array

Zero-length arrays are deprecated[1]. Replace struct i40e_lump_tracking's
"list" 0-length array with a flexible array. Detected with GCC 13,
using -fstrict-flex-arrays=3:

In function 'i40e_put_lump',
    inlined from 'i40e_clear_interrupt_scheme' at drivers/net/ethernet/intel/i40e/i40e_main.c:5145:2:
drivers/net/ethernet/intel/i40e/i40e_main.c:278:27: warning: array subscript <unknown> is outside array bounds of 'u16[0]' {aka 'short unsigned int[]'} [-Warray-bounds=]
  278 |                 pile->list[i] = 0;
      |                 ~~~~~~~~~~^~~
drivers/net/ethernet/intel/i40e/i40e.h: In function 'i40e_clear_interrupt_scheme':
drivers/net/ethernet/intel/i40e/i40e.h:179:13: note: while referencing 'list'
  179 |         u16 list[0];
      |             ^~~~

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays

Cc: Jesse Brandeburg <jesse.brandeburg@...el.com>
Cc: Tony Nguyen <anthony.l.nguyen@...el.com>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Jakub Kicinski <kuba@...nel.org>
Cc: Paolo Abeni <pabeni@...hat.com>
Cc: "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: intel-wired-lan@...ts.osuosl.org
Cc: netdev@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/net/ethernet/intel/i40e/i40e.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e.h b/drivers/net/ethernet/intel/i40e/i40e.h
index 60e351665c70..3a1c28ca5bb4 100644
--- a/drivers/net/ethernet/intel/i40e/i40e.h
+++ b/drivers/net/ethernet/intel/i40e/i40e.h
@@ -176,7 +176,7 @@ enum i40e_interrupt_policy {
 
 struct i40e_lump_tracking {
 	u16 num_entries;
-	u16 list[0];
+	u16 list[];
 #define I40E_PILE_VALID_BIT  0x8000
 #define I40E_IWARP_IRQ_PILE_ID  (I40E_PILE_VALID_BIT - 2)
 };
-- 
2.34.1