From: Jakub Kicinski <kuba@kernel.org>
To: Marc Kleine-Budde <mkl@pengutronix.de>,
Kees Cook <keescook@chromium.org>
Cc: Eric Dumazet <edumazet@google.com>,
netdev@vger.kernel.org, "David S. Miller" <davem@davemloft.net>
Subject: Re: ether_addr_equal_64bits breakage with gcc-12
Date: Fri, 11 Feb 2022 16:35:41 -0800 [thread overview]
Message-ID: <20220211163541.74b0836a@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> (raw)
In-Reply-To: <20220211141213.l4yitk7aifehjymp@pengutronix.de>
On Fri, 11 Feb 2022 15:12:13 +0100 Marc Kleine-Budde wrote:
> Hello,
>
> the current arm-linux-gnueabihf-gcc 12 snapshot in Debian breaks (at
> least with CONFIG_WERROR=y):
>
> | CC net/core/dev.o
> | net/core/dev.c: In function ‘bpf_prog_run_generic_xdp’:
> | net/core/dev.c:4618:21: warning: ‘ether_addr_equal_64bits’ reading 8 bytes from a region of size 6 [-Wstringop-overread]
> | 4618 | orig_host = ether_addr_equal_64bits(eth->h_dest, skb->dev->dev_addr);
> | | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> | net/core/dev.c:4618:21: note: referencing argument 1 of type ‘const u8[8]’ {aka ‘const unsigned char[8]’}
> | net/core/dev.c:4618:21: note: referencing argument 2 of type ‘const u8[8]’ {aka ‘const unsigned char[8]’}
> | In file included from net/core/dev.c:91:
> | include/linux/etherdevice.h:375:20: note: in a call to function ‘ether_addr_equal_64bits’
> | 375 | static inline bool ether_addr_equal_64bits(const u8 addr1[6+2],
> | | ^~~~~~~~~~~~~~~~~~~~~~~
> | net/core/dev.c:4619:22: warning: ‘is_multicast_ether_addr_64bits’ reading 8 bytes from a region of size 6 [-Wstringop-overread]
> | 4619 | orig_bcast = is_multicast_ether_addr_64bits(eth->h_dest);
> | | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> | net/core/dev.c:4619:22: note: referencing argument 1 of type ‘const u8[8]’ {aka ‘const unsigned char[8]’}
> | include/linux/etherdevice.h:137:20: note: in a call to function ‘is_multicast_ether_addr_64bits’
> | 137 | static inline bool is_multicast_ether_addr_64bits(const u8 addr[6+2])
> | | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> | net/core/dev.c:4646:27: warning: ‘ether_addr_equal_64bits’ reading 8 bytes from a region of size 6 [-Wstringop-overread]
> | 4646 | (orig_host != ether_addr_equal_64bits(eth->h_dest,
> | | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> | 4647 | skb->dev->dev_addr)) ||
> | | ~~~~~~~~~~~~~~~~~~~
> | net/core/dev.c:4646:27: note: referencing argument 1 of type ‘const u8[8]’ {aka ‘const unsigned char[8]’}
> | net/core/dev.c:4646:27: note: referencing argument 2 of type ‘const u8[8]’ {aka ‘const unsigned char[8]’}
> | include/linux/etherdevice.h:375:20: note: in a call to function ‘ether_addr_equal_64bits’
> | 375 | static inline bool ether_addr_equal_64bits(const u8 addr1[6+2],
> | | ^~~~~~~~~~~~~~~~~~~~~~~
> | net/core/dev.c:4648:28: warning: ‘is_multicast_ether_addr_64bits’ reading 8 bytes from a region of size 6 [-Wstringop-overread]
> | 4648 | (orig_bcast != is_multicast_ether_addr_64bits(eth->h_dest))) {
> | | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> | net/core/dev.c:4648:28: note: referencing argument 1 of type ‘const u8[8]’ {aka ‘const unsigned char[8]’}
> | include/linux/etherdevice.h:137:20: note: in a call to function ‘is_multicast_ether_addr_64bits’
> | 137 | static inline bool is_multicast_ether_addr_64bits(const u8 addr[6+2])
> | | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> | arm-linux-gnueabihf-gcc -v
> | Using built-in specs.
> | COLLECT_GCC=/usr/bin/arm-linux-gnueabihf-gcc
> | COLLECT_LTO_WRAPPER=/usr/lib/gcc-cross/arm-linux-gnueabihf/12/lto-wrapper
> | Target: arm-linux-gnueabihf
> | Configured with: ../src/configure -v --with-pkgversion='Debian 12-20220126-1' --with-bugurl=file:///usr/share/doc/gcc-12/README.Bugs --enable-languages=c,ada,c++,go,d,fortran,objc,obj-c++,m2 --prefix=/usr --with-gcc-major-version-only --program-suffix=-12 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-libitm --disable-libquadmath --disable-libquadmath-support --enable-plugin --enable-default-pie --with-system-zlib --enable-libphobos-checking=release --without-target-system-zlib --enable-multiarch --disable-sjlj-exceptions --with-arch=armv7-a+fp --with-float=hard --with-mode=thumb --disable-werror --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=arm-linux-gnueabihf --program-prefix=arm-linux-gnueabihf- --includedir=/usr/arm-linux-gnueabihf/include
> | Thread model: posix
> | Supported LTO compression algorithms: zlib zstd
> | gcc version 12.0.1 20220126 (experimental) [master r12-6872-gf3e6ef7d873] (Debian 12-20220126-1)
Maybe Kees will have as suggestion - Kees, are there any best practices
for dealing with such issues? For the reference we do a oversized load
from a structure (read 8B of a 6B array):
struct ethhdr {
unsigned char h_dest[6];
unsigned char h_source[6];
__be16 h_proto;
} __attribute__((packed));
But then discard the irrelevant bytes:
#if defined(CONFIG_HAVE_EFFICIENT...
u64 fold = (*(const u64 *)addr1) ^ (*(const u64 *)addr2);
#ifdef __BIG_ENDIAN
return (fold >> 16) == 0;
#else ...
The structure is uAPI, for added fun.
next prev parent reply other threads:[~2022-02-12 0:35 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-11 14:12 ether_addr_equal_64bits breakage with gcc-12 Marc Kleine-Budde
2022-02-12 0:35 ` Jakub Kicinski [this message]
2022-02-12 1:31 ` Kees Cook
2022-02-12 9:08 ` Marc Kleine-Budde
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