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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id b5sm7520197qkk.16.2020.03.05.20.50.52 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 05 Mar 2020 20:50:52 -0800 (PST) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 13.0 \(3608.60.0.2.5\)) Subject: Re: [PATCH -next v2] powerpc/64s/pgtable: fix an undefined behaviour From: Qian Cai In-Reply-To: Date: Thu, 5 Mar 2020 23:50:51 -0500 Cc: Michael Ellerman , Andrew Morton , rashmicy@gmail.com, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: References: <1583418759-16105-1-git-send-email-cai@lca.pw> To: Christophe Leroy X-Mailer: Apple Mail (2.3608.60.0.2.5) 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: > On Mar 5, 2020, at 2:22 PM, Christophe Leroy = wrote: >=20 >=20 >=20 > Le 05/03/2020 =C3=A0 15:32, Qian Cai a =C3=A9crit : >> Booting a power9 server with hash MMU could trigger an undefined >> behaviour because pud_offset(p4d, 0) will do, >> 0 >> (PAGE_SHIFT:16 + PTE_INDEX_SIZE:8 + H_PMD_INDEX_SIZE:10) >> Fix it by converting pud_offset() and friends to static inline >> functions. >=20 > I was suggesting to convert pud_index() to static inline, because = that's where the shift sits. Is it not possible ? >=20 > Here you seems to fix the problem for now, but if someone reuses = pud_index() in another macro one day, the same problem may happen again. >=20 Sounds reasonable. I send out a v3, https://lore.kernel.org/lkml/20200306044852.3236-1-cai@lca.pw/T/#u > Christophe >=20 >> UBSAN: shift-out-of-bounds in arch/powerpc/mm/ptdump/ptdump.c:282:15 >> shift exponent 34 is too large for 32-bit type 'int' >> CPU: 6 PID: 1 Comm: swapper/0 Not tainted 5.6.0-rc4-next-20200303+ = #13 >> Call Trace: >> dump_stack+0xf4/0x164 (unreliable) >> ubsan_epilogue+0x18/0x78 >> __ubsan_handle_shift_out_of_bounds+0x160/0x21c >> walk_pagetables+0x2cc/0x700 >> walk_pud at arch/powerpc/mm/ptdump/ptdump.c:282 >> (inlined by) walk_pagetables at arch/powerpc/mm/ptdump/ptdump.c:311 >> ptdump_check_wx+0x8c/0xf0 >> mark_rodata_ro+0x48/0x80 >> kernel_init+0x74/0x194 >> ret_from_kernel_thread+0x5c/0x74 >> Suggested-by: Christophe Leroy >> Signed-off-by: Qian Cai >> --- >> arch/powerpc/include/asm/book3s/64/pgtable.h | 20 = ++++++++++++++------ >> 1 file changed, 14 insertions(+), 6 deletions(-) >> diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h = b/arch/powerpc/include/asm/book3s/64/pgtable.h >> index fa60e8594b9f..4967bc9e25e2 100644 >> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h >> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h >> @@ -1016,12 +1016,20 @@ static inline bool p4d_access_permitted(p4d_t = p4d, bool write) >> #define pgd_offset(mm, address) ((mm)->pgd + = pgd_index(address)) >> -#define pud_offset(p4dp, addr) \ >> - (((pud_t *) p4d_page_vaddr(*(p4dp))) + pud_index(addr)) >> -#define pmd_offset(pudp,addr) \ >> - (((pmd_t *) pud_page_vaddr(*(pudp))) + pmd_index(addr)) >> -#define pte_offset_kernel(dir,addr) \ >> - (((pte_t *) pmd_page_vaddr(*(dir))) + pte_index(addr)) >> +static inline pud_t *pud_offset(p4d_t *p4d, unsigned long address) >> +{ >> + return (pud_t *)p4d_page_vaddr(*p4d) + pud_index(address); >> +} >> + >> +static inline pmd_t *pmd_offset(pud_t *pud, unsigned long address) >> +{ >> + return (pmd_t *)pud_page_vaddr(*pud) + pmd_index(address); >> +} >> + >> +static inline pte_t *pte_offset_kernel(pmd_t *pmd, unsigned long = address) >> +{ >> + return (pte_t *)pmd_page_vaddr(*pmd) + pte_index(address); >> +} >> #define pte_offset_map(dir,addr) pte_offset_kernel((dir), (addr)) >> =20