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Tue, 3 Feb 2026 11:38:16 +0800 (CST) Received: from [10.174.179.179] (10.174.179.179) by kwepemr500001.china.huawei.com (7.202.194.229) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Tue, 3 Feb 2026 11:38:16 +0800 Message-ID: <73396cda-e12c-484f-ab84-b09e7aab8bb0@huawei.com> Date: Tue, 3 Feb 2026 11:38:15 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] arm64: mm: fix pass user prot to ioremap_prot in generic_access_phys To: Will Deacon CC: , , , , , , , , References: <20260130073807.99474-1-tujinjiang@huawei.com> From: Jinjiang Tu In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.179.179] X-ClientProxiedBy: kwepems100001.china.huawei.com (7.221.188.238) To kwepemr500001.china.huawei.com (7.202.194.229) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260202_193831_926904_9B668F33 X-CRM114-Status: GOOD ( 20.45 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 在 2026/2/2 22:55, Will Deacon 写道: > On Fri, Jan 30, 2026 at 03:38:07PM +0800, Jinjiang Tu wrote: >> Here is a syzkaller error log: >> [0000000020ffc000] pgd=080000010598d403, p4d=080000010598d403, pud=0800000125ddb403, >> pmd=080000007833c403, pte=01608000007fcfcf >> Unable to handle kernel read from unreadable memory at virtual address ffff80008ea89000 >> KASAN: probably user-memory-access in range [0x0000000475448000-0x0000000475448007] >> Mem abort info: >> ESR = 0x000000009600000f >> EC = 0x25: DABT (current EL), IL = 32 bits >> SET = 0, FnV = 0 >> EA = 0, S1PTW = 0 >> FSC = 0x0f: level 3 permission fault >> Data abort info: >> ISV = 0, ISS = 0x0000000f, ISS2 = 0x00000000 >> CM = 0, WnR = 0, TnD = 0, TagAccess = 0 >> GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 >> swapper pgtable: 4k pages, 48-bit VAs, pgdp=00000001244aa000 >> [ffff80008ea89000] pgd=100000013ffff403, p4d=100000013ffff403, pud=100000013fffe403, >> pmd=100000010a453403, pte=01608000007fcfcf >> Internal error: Oops: 000000009600000f [#1] SMP >> Modules linked in: team >> CPU: 1 PID: 10840 Comm: syz.9.83 Kdump: loaded Tainted: G >> Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015 >> pstate: 20400005 (nzCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) >> pc : __memcpy_fromio+0x80/0xf8 >> lr : generic_access_phys+0x20c/0x2b8 >> sp : ffff8000a0507960 >> x29: ffff8000a0507960 x28: 1ffff000140a0f44 x27: ffff00003833cfe0 >> x26: 0000000000000000 x25: 0000000000001000 x24: 0010000000000001 >> x23: ffff80008ea89000 x22: ffff00004ea63000 x21: 0000000000001000 >> x20: ffff80008ea89000 x19: ffff00004ea62000 x18: 0000000000000000 >> x17: 0000000000000000 x16: 0000000000000000 x15: ffff8000806f1e3c >> x14: ffff8000806f1d44 x13: 0000000041b58ab3 x12: ffff7000140a0f23 >> x11: 1ffff000140a0f22 x10: ffff7000140a0f22 x9 : ffff800080579d24 >> x8 : 0000000000000004 x7 : 0000000000000003 x6 : 0000000000000001 >> x5 : ffff8000a0507910 x4 : ffff7000140a0f22 x3 : dfff800000000000 >> x2 : 0000000000001000 x1 : ffff80008ea89000 x0 : ffff00004ea62000 >> Call trace: >> __memcpy_fromio+0x80/0xf8 >> generic_access_phys+0x20c/0x2b8 >> __access_remote_vm+0x46c/0x5b8 >> access_remote_vm+0x18/0x30 >> environ_read+0x238/0x3e8 >> vfs_read+0xe4/0x2b0 >> ksys_read+0xcc/0x178 >> __arm64_sys_read+0x4c/0x68 >> invoke_syscall+0x68/0x1a0 >> el0_svc_common.constprop.0+0x11c/0x150 >> do_el0_svc+0x38/0x50 >> el0_svc+0x50/0x258 >> el0t_64_sync_handler+0xc0/0xc8 >> el0t_64_sync+0x1a4/0x1a8 >> Code: 91002339 aa1403f7 8b190276 d503201f (f94002f8) >> >> The local syzkaller first maps I/O address from /dev/mem to userspace, >> overiding the stack vma with MAP_FIXED flag. As a result, when reading >> /proc/$pid/environ, generic_access_phys() is called to access the region, >> which triggers a PAN permission-check fault and causes a kernel access >> fault. >> >> The root cause is that generic_access_phys() passes a user pte to >> ioremap_prot(), the user pte sets PTE_USER and PTE_NG bits. Consequently, >> any subsequent kernel-mode access to the remapped address raises a fault. >> >> To fix it, define arch_mk_kernel_prot() to convert user prot to kernel >> prot for arm64, and call arch_mk_kernel_prot() in generic_access_phys(), >> so that a user prot is passed to ioremap_prot(). >> >> Fixes: 893dea9ccd08 ("arm64: Add HAVE_IOREMAP_PROT support") >> Signed-off-by: Zeng Heng >> Signed-off-by: Jinjiang Tu >> --- >> Changes in v3: >> * arch_mk_kernel_prot() always grant read/write permissions. >> >> arch/arm64/include/asm/io.h | 8 ++++++++ >> mm/memory.c | 12 +++++++++++- >> 2 files changed, 19 insertions(+), 1 deletion(-) >> >> diff --git a/arch/arm64/include/asm/io.h b/arch/arm64/include/asm/io.h >> index 83e03abbb2ca..fe3040d59119 100644 >> --- a/arch/arm64/include/asm/io.h >> +++ b/arch/arm64/include/asm/io.h >> @@ -267,6 +267,14 @@ int arm64_ioremap_prot_hook_register(const ioremap_prot_hook_t hook); >> >> #define ioremap_prot ioremap_prot >> >> +#define arch_mk_kernel_prot arch_mk_kernel_prot >> +static inline pgprot_t arch_mk_kernel_prot(pgprot_t user_prot) >> +{ >> + ptdesc_t mem_type = pgprot_val(user_prot) & PTE_ATTRINDX_MASK; >> + >> + return __pgprot_modify(PAGE_KERNEL, PTE_ATTRINDX_MASK, mem_type); >> +} > Do we really need another arch helper here? For arc, powerpc, ioremap_prot() simply copy the user pte prot to the kernel page table too. So maybe we should fix for the two archs too, and we should define a arch helper here. But I'm not familiar with them. > > It looks to me like generic_access_phys() is the only caller of > ioremap_prot() outside of arch/, so why not just handle the user_prot in > there on arm64? You could rename the existing ioremap_prot() function in > arch/arm64/mm/ioremap.c to e.g. __ioremap_prot(), switch over the > callers in arch/arm64 and then add ioremap_prot() to wrap that with your > pgprot modification above. > > Will >