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Thu, 01 Feb 2024 06:08:46 -0800 (PST) MIME-Version: 1.0 References: <20240201090434.1762340-1-elver@google.com> In-Reply-To: <20240201090434.1762340-1-elver@google.com> From: Andrey Konovalov Date: Thu, 1 Feb 2024 15:08:35 +0100 Message-ID: Subject: Re: [PATCH -mm v2] stackdepot: fix -Wstringop-overflow warning To: Marco Elver Cc: Andrew Morton , Alexander Potapenko , Dmitry Vyukov , Vlastimil Babka , linux-kernel@vger.kernel.org, linux-mm@kvack.org, kasan-dev@googlegroups.com, Stephen Rothwell Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 3922A20023 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: ncp6ebjiktgqscdsz3hu77tum53zymoi X-HE-Tag: 1706796527-457861 X-HE-Meta: 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 9CJEv8IA 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Feb 1, 2024 at 10:04=E2=80=AFAM Marco Elver wrot= e: > > Since 113a61863ecb ("Makefile: Enable -Wstringop-overflow globally") > string overflow checking is enabled by default. Within stackdepot, the > compiler (GCC 13.2.0) assumes that a multiplication overflow may be > possible and flex_array_size() can return SIZE_MAX (4294967295 on > 32-bit), resulting in this warning: > > In function 'depot_alloc_stack', > inlined from 'stack_depot_save_flags' at lib/stackdepot.c:688:4: > arch/x86/include/asm/string_32.h:150:25: error: '__builtin_memcpy' speci= fied bound 4294967295 exceeds maximum object size 2147483647 [-Werror=3Dstr= ingop-overflow=3D] > 150 | #define memcpy(t, f, n) __builtin_memcpy(t, f, n) > | ^~~~~~~~~~~~~~~~~~~~~~~~~ > lib/stackdepot.c:459:9: note: in expansion of macro 'memcpy' > 459 | memcpy(stack->entries, entries, flex_array_size(stack, e= ntries, nr_entries)); > | ^~~~~~ > cc1: all warnings being treated as errors > > This is due to depot_alloc_stack() accepting an 'int nr_entries' which > could be negative without deeper analysis of callers. > > The call to depot_alloc_stack() from stack_depot_save_flags(), however, > only passes in its nr_entries which is unsigned int. Fix the warning by > switching depot_alloc_stack()'s nr_entries to also be unsigned. > > Link: https://lore.kernel.org/all/20240201135747.18eca98e@canb.auug.org.a= u/ > Fixes: d869d3fb362c ("stackdepot: use variable size records for non-evict= able entries") > Reported-by: Stephen Rothwell > Signed-off-by: Marco Elver > --- > v2: > * Just switch 'nr_entries' to unsigned int which is already the case > elsewhere. > --- > lib/stackdepot.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/lib/stackdepot.c b/lib/stackdepot.c > index 8f3b2c84ec2d..4a7055a63d9f 100644 > --- a/lib/stackdepot.c > +++ b/lib/stackdepot.c > @@ -420,7 +420,7 @@ static inline size_t depot_stack_record_size(struct s= tack_record *s, unsigned in > > /* Allocates a new stack in a stack depot pool. */ > static struct stack_record * > -depot_alloc_stack(unsigned long *entries, int nr_entries, u32 hash, depo= t_flags_t flags, void **prealloc) > +depot_alloc_stack(unsigned long *entries, unsigned int nr_entries, u32 h= ash, depot_flags_t flags, void **prealloc) > { > struct stack_record *stack =3D NULL; > size_t record_size; > -- > 2.43.0.429.g432eaa2c6b-goog > Reviewed-by: Andrey Konovalov