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Message-ID: <Z1Cvs1xNSDQRJ1Ri@google.com> Date: Wed, 4 Dec 2024 11:38:27 -0800 From: Brian Norris <briannorris@...omium.org> To: Nilay Shroff <nilay@...ux.ibm.com> Cc: linux-kernel@...r.kernel.org, kees@...nel.org, nathan@...nel.org, yury.norov@...il.com, linux@...ssschuh.net, gjoyce@....com, Steffen Klassert <steffen.klassert@...unet.com>, Daniel Jordan <daniel.m.jordan@...cle.com>, linux-crypto@...r.kernel.org Subject: Re: [PATCH] cpumask: work around false-postive stringop-overread errors Hi Nilay, I see you didn't CC the maintainers for this file. You might consider looking through: https://www.kernel.org/doc/html/latest/process/submitting-patches.html And: $ scripts/get_maintainer.pl -f kernel/padata.c Steffen Klassert <steffen.klassert@...unet.com> (maintainer:PADATA PARALLEL EXECUTION MECHANISM) Daniel Jordan <daniel.m.jordan@...cle.com> (maintainer:PADATA PARALLEL EXECUTION MECHANISM) linux-crypto@...r.kernel.org (open list:PADATA PARALLEL EXECUTION MECHANISM) linux-kernel@...r.kernel.org (open list:PADATA PARALLEL EXECUTION MECHANISM) I'll leave the full contents intact below for their sake, with a few inline comments as well: On Tue, Nov 12, 2024 at 06:11:24PM +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, > | ~~~~~~~~~~~~~~^~~~~~~~ > > Apparentrly, above errors only menifests 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 erros 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. You might consider running this paragraph through a spelling checker if you submit a v2. > Link: https://lore.kernel.org/all/7cbbd751-8332-4ab2-afa7-8c353834772a@linux.ibm.com/ > Cc: briannorris@...omium.org > Cc: kees@...nel.org > Cc: nathan@...nel.org > Cc: yury.norov@...il.com > Cc: linux@...ssschuh.net > Cc: gjoyce@....com > Signed-off-by: Nilay Shroff <nilay@...ux.ibm.com> > --- > kernel/Makefile | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/kernel/Makefile b/kernel/Makefile > index 87866b037fbe..e5adba7a30f1 100644 > --- a/kernel/Makefile > +++ b/kernel/Makefile > @@ -120,6 +120,7 @@ obj-$(CONFIG_CFI_CLANG) += cfi.o > obj-$(CONFIG_PERF_EVENTS) += events/ > > obj-$(CONFIG_USER_RETURN_NOTIFIER) += user-return-notifier.o > +CFLAGS_padata.o += $(call cc-disable-warning, stringop-overread) Personally, I'd recommend a comment here, noting that these warnings seem to produce false positives on GCC 13+. But otherwise, this seems OK to me: Reviewed-by: Brian Norris <briannorris@...omium.org> > obj-$(CONFIG_PADATA) += padata.o > obj-$(CONFIG_JUMP_LABEL) += jump_label.o > obj-$(CONFIG_CONTEXT_TRACKING) += context_tracking.o > -- > 2.45.2 >
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