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Fri, 6 Nov 2020 09:25:06 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id CF2625204F; Fri, 6 Nov 2020 09:25:05 +0000 (GMT) Received: from linux.ibm.com (unknown [9.145.7.6]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTPS id B29065204E; Fri, 6 Nov 2020 09:25:04 +0000 (GMT) Date: Fri, 6 Nov 2020 11:25:02 +0200 From: Mike Rapoport To: Linus Walleij Subject: Re: [PATCH] mm: kasan: Index page hierarchy as an array Message-ID: <20201106092502.GE301789@linux.ibm.com> References: <20201106085157.11211-1-linus.walleij@linaro.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201106085157.11211-1-linus.walleij@linaro.org> X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312, 18.0.737 definitions=2020-11-06_03:2020-11-05, 2020-11-06 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 lowpriorityscore=0 malwarescore=0 priorityscore=1501 mlxlogscore=999 clxscore=1011 adultscore=0 impostorscore=0 bulkscore=0 spamscore=0 mlxscore=0 suspectscore=5 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011060066 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201106_042521_858986_0674B8AB X-CRM114-Status: GOOD ( 33.26 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kernel test robot , Arnd Bergmann , kasan-dev@googlegroups.com, Alexander Potapenko , Dmitry Vyukov , Andrey Ryabinin , Ard Biesheuvel , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Nov 06, 2020 at 09:51:57AM +0100, Linus Walleij wrote: > When freeing page directories, KASan was consistently > indexing through the page hierarchy like this: > > static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d) { > pud_t *pud; > int i; > > for (i = 0; i < PTRS_PER_PUD; i++) { > pud = pud_start + i; > if (!pud_none(*pud)) > if (!pud_none(pud_start[i])) > return; > } > } > > That is: implicitly add i sizeof(put_t) idices to > the variable pud. > > On ARM32 arch/arm/include/asm/pgtable-2level.h has folded > the PMDs into the PUDs and thus has this definition of > pud_none(): > > #define pud_none(pud) (0) > > This will make the above construction emit this harmless > build warning on ARM32: > > mm/kasan/init.c: In function 'kasan_free_pud': > >> mm/kasan/init.c:318:9: warning: variable 'pud' set but not used [-Wunused-but-set-variable] > 318 | pud_t *pud; > | ^~~ > > Using an explicit array removes this problem and also makes > the build warning go away. Arguably the code also gets > easier to read. > > So I fixed all the kasan_free_p??() to use explicit > array inidices instead. > > Fixes: 421015713b30 ("ARM: 9017/2: Enable KASan for ARM") > Reported-by: kernel test robot > Suggested-by: Ard Biesheuvel > Signed-off-by: Linus Walleij Acked-by: Mike Rapoport > --- > mm/kasan/init.c | 16 ++++------------ > 1 file changed, 4 insertions(+), 12 deletions(-) > > diff --git a/mm/kasan/init.c b/mm/kasan/init.c > index fe6be0be1f76..3c74c30996ef 100644 > --- a/mm/kasan/init.c > +++ b/mm/kasan/init.c > @@ -285,12 +285,10 @@ int __ref kasan_populate_early_shadow(const void *shadow_start, > > static void kasan_free_pte(pte_t *pte_start, pmd_t *pmd) > { > - pte_t *pte; > int i; > > for (i = 0; i < PTRS_PER_PTE; i++) { > - pte = pte_start + i; > - if (!pte_none(*pte)) > + if (!pte_none(pte_start[i])) > return; > } > > @@ -300,12 +298,10 @@ static void kasan_free_pte(pte_t *pte_start, pmd_t *pmd) > > static void kasan_free_pmd(pmd_t *pmd_start, pud_t *pud) > { > - pmd_t *pmd; > int i; > > for (i = 0; i < PTRS_PER_PMD; i++) { > - pmd = pmd_start + i; > - if (!pmd_none(*pmd)) > + if (!pmd_none(pmd_start[i])) > return; > } > > @@ -315,12 +311,10 @@ static void kasan_free_pmd(pmd_t *pmd_start, pud_t *pud) > > static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d) > { > - pud_t *pud; > int i; > > for (i = 0; i < PTRS_PER_PUD; i++) { > - pud = pud_start + i; > - if (!pud_none(*pud)) > + if (!pud_none(pud_start[i])) > return; > } > > @@ -330,12 +324,10 @@ static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d) > > static void kasan_free_p4d(p4d_t *p4d_start, pgd_t *pgd) > { > - p4d_t *p4d; > int i; > > for (i = 0; i < PTRS_PER_P4D; i++) { > - p4d = p4d_start + i; > - if (!p4d_none(*p4d)) > + if (!p4d_none(p4d_start[i])) > return; > } > > -- > 2.26.2 > -- Sincerely yours, Mike. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel