On 12/7/24 17:14, Greg KH wrote: > On Sat, Dec 07, 2024 at 12:43:19PM +0100, Greg KH wrote: >> On Thu, Dec 05, 2024 at 06:04:09PM +0530, Nilay Shroff wrote: >>> While building the powerpc code using gcc 13, I came across following >>> errors generated for kernel/padata.c file: >>> >>> CC kernel/padata.o >>> In file included from ./include/linux/string.h:390, >>> from ./arch/powerpc/include/asm/paca.h:16, >>> from ./arch/powerpc/include/asm/current.h:13, >>> from ./include/linux/thread_info.h:23, >>> from ./include/asm-generic/preempt.h:5, >>> from ./arch/powerpc/include/generated/asm/preempt.h:1, >>> from ./include/linux/preempt.h:79, >>> from ./include/linux/spinlock.h:56, >>> from ./include/linux/swait.h:7, >>> from ./include/linux/completion.h:12, >>> from kernel/padata.c:14: >>> In function ‘bitmap_copy’, >>> inlined from ‘cpumask_copy’ at ./include/linux/cpumask.h:839:2, >>> inlined from ‘__padata_set_cpumasks’ at kernel/padata.c:730:2: >>> ./include/linux/fortify-string.h:114:33: error: ‘__builtin_memcpy’ reading between 257 and 536870904 bytes from a region of size 256 [-Werror=stringop-overread] >>> 114 | #define __underlying_memcpy __builtin_memcpy >>> | ^ >>> ./include/linux/fortify-string.h:633:9: note: in expansion of macro ‘__underlying_memcpy’ >>> 633 | __underlying_##op(p, q, __fortify_size); \ >>> | ^~~~~~~~~~~~~ >>> ./include/linux/fortify-string.h:678:26: note: in expansion of macro ‘__fortify_memcpy_chk’ >>> 678 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ >>> | ^~~~~~~~~~~~~~~~~~~~ >>> ./include/linux/bitmap.h:259:17: note: in expansion of macro ‘memcpy’ >>> 259 | memcpy(dst, src, len); >>> | ^~~~~~ >>> kernel/padata.c: In function ‘__padata_set_cpumasks’: >>> kernel/padata.c:713:48: note: source object ‘pcpumask’ of size [0, 256] >>> 713 | cpumask_var_t pcpumask, >>> | ~~~~~~~~~~~~~~^~~~~~~~ >>> In function ‘bitmap_copy’, >>> inlined from ‘cpumask_copy’ at ./include/linux/cpumask.h:839:2, >>> inlined from ‘__padata_set_cpumasks’ at kernel/padata.c:730:2: >>> ./include/linux/fortify-string.h:114:33: error: ‘__builtin_memcpy’ reading between 257 and 536870904 bytes from a region of size 256 [-Werror=stringop-overread] >>> 114 | #define __underlying_memcpy __builtin_memcpy >>> | ^ >>> ./include/linux/fortify-string.h:633:9: note: in expansion of macro ‘__underlying_memcpy’ >>> 633 | __underlying_##op(p, q, __fortify_size); \ >>> | ^~~~~~~~~~~~~ >>> ./include/linux/fortify-string.h:678:26: note: in expansion of macro ‘__fortify_memcpy_chk’ >>> 678 | #define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \ >>> | ^~~~~~~~~~~~~~~~~~~~ >>> ./include/linux/bitmap.h:259:17: note: in expansion of macro ‘memcpy’ >>> 259 | memcpy(dst, src, len); >>> | ^~~~~~ >>> kernel/padata.c: In function ‘__padata_set_cpumasks’: >>> kernel/padata.c:713:48: note: source object ‘pcpumask’ of size [0, 256] >>> 713 | cpumask_var_t pcpumask, >>> | ~~~~~~~~~~~~~~^~~~~~~~ >>> >>> Apparently, above errors only manifests with GCC 13.x and config option >>> CONFIG_FORTIFY_SOURCE. Furthermore, if I use gcc 11.x or gcc 12.x then I >>> don't encounter above errors. Prima facie, these errors appear to be false- >>> positive. Brian informed me that currently some efforts are underway by >>> GCC developers to emit more verbose information when GCC detects string >>> overflow errors and that might help to further narrow down the root cause >>> of this error. So for now, silence these errors using -Wno-stringop- >>> overread gcc option while building kernel/padata.c file until we find the >>> root cause. >> >> I'm hitting this now on Linus's tree using gcc14 on x86-64 so this isn't >> just a problem with your arch. Thanks Greg for confirming that this is not isolated to PowerPC!! >> >> Let me try this patch locally and see if it helps... > > Yes, fixes the build for me, so either this is a real fix, or something > else needs to be done for it, so I'll give a: > > Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > > for now. Okay so now we've an evidence confirming that this is no longer PowerPC specific issue. Hence as Yury suggested, in another mail[1], fixing this error by disabling stringop-overread globally for GCC13+ and CONFIG_FORTIFY_SOURCE=n, I will spin a new patch and submit it. [1] https://lore.kernel.org/all/Z1HTdtvNjm-nZSvJ@yury-ThinkPad/ Thanks, --Nilay
