mainline build failure due to 332f1795ca20 ("Bluetooth: L2CAP: Fix l2cap_global_chan_by_psm regression")

[Sudip Mukherjee (Codethink)]

Hi All,

The latest mainline kernel branch fails to build csky and mips allmodconfig
with gcc-12.

mips error is:

In function 'memcmp',
    inlined from 'bacmp' at ./include/net/bluetooth/bluetooth.h:347:9,
    inlined from 'l2cap_global_chan_by_psm' at net/bluetooth/l2cap_core.c:2003:15:
./include/linux/fortify-string.h:44:33: error: '__builtin_memcmp' specified bound 6 exceeds source size 0 [-Werror=stringop-overread]
   44 | #define __underlying_memcmp     __builtin_memcmp
      |                                 ^
./include/linux/fortify-string.h:420:16: note: in expansion of macro '__underlying_memcmp'
  420 |         return __underlying_memcmp(p, q, size);
      |                ^~~~~~~~~~~~~~~~~~~
In function 'memcmp',
    inlined from 'bacmp' at ./include/net/bluetooth/bluetooth.h:347:9,
    inlined from 'l2cap_global_chan_by_psm' at net/bluetooth/l2cap_core.c:2004:15:
./include/linux/fortify-string.h:44:33: error: '__builtin_memcmp' specified bound 6 exceeds source size 0 [-Werror=stringop-overread]
   44 | #define __underlying_memcmp     __builtin_memcmp
      |                                 ^
./include/linux/fortify-string.h:420:16: note: in expansion of macro '__underlying_memcmp'
  420 |         return __underlying_memcmp(p, q, size);
      |                ^~~~~~~~~~~~~~~~~~~


csky error is:

In file included from net/bluetooth/l2cap_core.c:37:
In function 'bacmp',
    inlined from 'l2cap_global_chan_by_psm' at net/bluetooth/l2cap_core.c:2003:15:
./include/net/bluetooth/bluetooth.h:347:16: error: 'memcmp' specified bound 6 exceeds source size 0 [-Werror=stringop-overread]
  347 |         return memcmp(ba1, ba2, sizeof(bdaddr_t));
      |                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In function 'bacmp',
    inlined from 'l2cap_global_chan_by_psm' at net/bluetooth/l2cap_core.c:2004:15:
./include/net/bluetooth/bluetooth.h:347:16: error: 'memcmp' specified bound 6 exceeds source size 0 [-Werror=stringop-overread]
  347 |         return memcmp(ba1, ba2, sizeof(bdaddr_t));
      |                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


git bisect pointed to 332f1795ca20 ("Bluetooth: L2CAP: Fix l2cap_global_chan_by_psm regression").
And, reverting that commit has fixed the build failure.

Already reported at https://lore.kernel.org/lkml/YvVQEDs75pxSgxjM@debian/
and Jacub is looking at a fix, but this is just my usual build failure
mail of mainline branch for Linus's information.


--
Regards
Sudip