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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id f13sm10558859qkm.42.2020.03.04.20.48.12 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 04 Mar 2020 20:48:12 -0800 (PST) From: Qian Cai To: mpe@ellerman.id.au, akpm@linux-foundation.org Cc: rashmicy@gmail.com, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Qian Cai Subject: [PATCH -next] powerpc/mm/ptdump: fix an undefined behaviour Date: Wed, 4 Mar 2020 23:47:59 -0500 Message-Id: <20200305044759.1279-1-cai@lca.pw> X-Mailer: git-send-email 2.21.0 (Apple Git-122.2) MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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) 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 Fixes: 8eb07b187000 ("powerpc/mm: Dump linux pagetables") Signed-off-by: Qian Cai --- Notes for maintainers: This is on the top of the linux-next commit "powerpc: add support for folded p4d page tables" which is in the Andrew's tree. arch/powerpc/mm/ptdump/ptdump.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/powerpc/mm/ptdump/ptdump.c b/arch/powerpc/mm/ptdump/ptdump.c index 9d6256b61df3..b530f81398a7 100644 --- a/arch/powerpc/mm/ptdump/ptdump.c +++ b/arch/powerpc/mm/ptdump/ptdump.c @@ -279,7 +279,7 @@ static void walk_pmd(struct pg_state *st, pud_t *pud, unsigned long start) static void walk_pud(struct pg_state *st, p4d_t *p4d, unsigned long start) { - pud_t *pud = pud_offset(p4d, 0); + pud_t *pud = pud_offset(p4d, 0UL); unsigned long addr; unsigned int i; -- 2.21.0 (Apple Git-122.2)