linux-kernel - mainline build failure due to df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3")

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Message-ID: <ZJ2M4yqnOCqqGWH0@debian>
Date:   Thu, 29 Jun 2023 14:53:39 +0100
From:   "Sudip Mukherjee (Codethink)" <sudipm.mukherjee@...il.com>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Kees Cook <keescook@...omium.org>
Cc:     linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        regressions@...ts.linux.dev
Subject: mainline build failure due to df8fc4e934c1 ("kbuild: Enable
 -fstrict-flex-arrays=3")

Hi All,

The latest mainline kernel branch fails to build with clang (version 16.0.1), and the errors are like:


drivers/scsi/aacraid/commsup.c:1170:17: error: array index 1 is past the end of the array (that has type 'u8[1]' (aka 'unsigned char[1]'), cast to '__le32 *' (aka 'unsigned int *')) [-Werror,-Warray-bounds]
                                (((__le32 *)aifcmd->data)[1] == cpu_to_le32(3));
                                            ^             ~
drivers/scsi/aacraid/aacraid.h:2621:2: note: array 'data' declared here
        u8 data[1];             /* Undefined length (from kernel viewpoint) */
        ^
drivers/scsi/aacraid/commsup.c:1290:20: error: array index 3 is past the end of the array (that has type 'u8[1]' (aka 'unsigned char[1]'), cast to '__le32 *' (aka 'unsigned int *')) [-Werror,-Warray-bounds]
                                  ((((__le32 *)aifcmd->data)[3]
                                               ^

_______________________________________________________________________


drivers/staging/ks7010/ks_wlan_net.c:1600:34: error: array index 16 is past the end of the array (that has type '__u8[0]' (aka 'unsigned char[0]')) [-Werror,-Warray-bounds]
                                memcpy(&key->tx_mic_key[0], &enc->key[16], 8);
                                                             ^        ~~
./include/linux/fortify-string.h:694:35: note: expanded from macro 'memcpy'
                __struct_size(p), __struct_size(q),                     \
                                                ^
./include/linux/fortify-string.h:96:56: note: expanded from macro '__struct_size'
#define __struct_size(p)        __builtin_dynamic_object_size(p, 0)
                                                              ^
./include/linux/fortify-string.h:638:27: note: expanded from macro '__fortify_memcpy_chk'
        const size_t __q_size = (q_size);                               \
                                 ^~~~~~
./include/uapi/linux/wireless.h:838:2: note: array 'key' declared here
        __u8            key[0];
        ^

_______________________________________________________________________


git bisect pointed to df8fc4e934c1 ("kbuild: Enable -fstrict-flex-arrays=3").

Reverting the commit has fixed the build failure.

I will be happy to test any patch or provide any extra log if needed.

#regzbot introduced: df8fc4e934c12b906d08050d7779f292b9c5c6b5


-- 
Regards
Sudip