When compiling with gcc 13 and CONFIG_FORTIFY_SOURCE=y, the following warning appears: In function ‘fortify_memcpy_chk’, inlined from ‘size_entry_mwt’ at net/bridge/netfilter/ebtables.c:2118:2: ./include/linux/fortify-string.h:592:25: error: call to ‘__read_overflow2_field’ declared with attribute warning: detected read beyond size of field (2nd parameter); maybe use struct_group()? [-Werror=attribute-warning] 592 | __read_overflow2_field(q_size_field, size); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The compiler is complaining: memcpy(&offsets[1], &entry->watchers_offset, sizeof(offsets) - sizeof(offsets[0])); where memcpy reads beyong &entry->watchers_offset to copy {watchers,target,next}_offset altogether into offsets[]. Silence the warning by wrapping these three up via struct_group().
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| @@ -182,12 +182,14 @@ struct ebt_entry { · 181 unmodified lines | |||
| 182 | unsigned char sourcemsk[ETH_ALEN]; | 182 | unsigned char sourcemsk[ETH_ALEN]; |
| 183 | unsigned char destmac[ETH_ALEN]; | 183 | unsigned char destmac[ETH_ALEN]; |
| 184 | unsigned char destmsk[ETH_ALEN]; | 184 | unsigned char destmsk[ETH_ALEN]; |
| 185 | /* sizeof ebt_entry + matches */ | 185 | __struct_group(/* no tag */, offsets, /* no attrs */, |
| 186 | unsigned int watchers_offset; | 186 | /* sizeof ebt_entry + matches */ |
| 187 | /* sizeof ebt_entry + matches + watchers */ | 187 | unsigned int watchers_offset; |
| 188 | unsigned int target_offset; | 188 | /* sizeof ebt_entry + matches + watchers */ |
| 189 | /* sizeof ebt_entry + matches + watchers + target */ | 189 | unsigned int target_offset; |
| 190 | unsigned int next_offset; | 190 | /* sizeof ebt_entry + matches + watchers + target */ |
| 191 | unsigned int next_offset; | ||
| 192 | ); | ||
| 191 | unsigned char elems[0] __attribute__ ((aligned (__alignof__(struct ebt_replace)))); | 193 | unsigned char elems[0] __attribute__ ((aligned (__alignof__(struct ebt_replace)))); |
| 192 | }; | 194 | }; |
| 193 | 195 | ||