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Re: [PATCH] arm64: mm: explicitly use kernel pte for ioremap_prot() To: Catalin Marinas CC: , , , , , , , , References: <20260123030238.835748-1-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: kwepems200002.china.huawei.com (7.221.188.68) To kwepemr500001.china.huawei.com (7.202.194.229) X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: D4A131A0002 X-Stat-Signature: iikqer73795fhck8ozyb7kcywgu3zwzt X-Rspam-User: X-HE-Tag: 1769394342-747547 X-HE-Meta: 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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, similar to ioremap_prot() in x86, use _PAGE_KERNEL as template, >> and update PTE_WRITE and PTE_ATTRINDX according to the pgprot argument. >> >> Fixes: 893dea9ccd08 ("arm64: Add HAVE_IOREMAP_PROT support") >> Signed-off-by: Zeng Heng >> Signed-off-by: Jinjiang Tu >> --- >> arch/arm64/mm/ioremap.c | 6 ++++++ >> 1 file changed, 6 insertions(+) >> >> diff --git a/arch/arm64/mm/ioremap.c b/arch/arm64/mm/ioremap.c >> index 10e246f11271..78a63a14465f 100644 >> --- a/arch/arm64/mm/ioremap.c >> +++ b/arch/arm64/mm/ioremap.c >> @@ -18,6 +18,7 @@ void __iomem *ioremap_prot(phys_addr_t phys_addr, size_t size, >> pgprot_t pgprot) >> { >> unsigned long last_addr = phys_addr + size - 1; >> + unsigned long new_pgprot_val; >> >> /* Don't allow outside PHYS_MASK */ >> if (last_addr & ~PHYS_MASK) >> @@ -27,6 +28,11 @@ void __iomem *ioremap_prot(phys_addr_t phys_addr, size_t size, >> if (WARN_ON(pfn_is_map_memory(__phys_to_pfn(phys_addr)))) >> return NULL; >> >> + new_pgprot_val = _PAGE_KERNEL & ~(PTE_WRITE | PTE_ATTRINDX_MASK); >> + new_pgprot_val |= (pgprot_val(pgprot) & PTE_WRITE) >> + | (pgprot_val(pgprot) & PTE_ATTRINDX_MASK); >> + pgprot = __pgprot(new_pgprot_val); >> + >> /* >> * If a hook is registered (e.g. for confidential computing >> * purposes), call that now and barf if it fails. > generic_access_phys() is really weird - it takes the user PTE attributes > and passes them to the kernel ioremap_prot(), hoping for the best. My > immediate thought was to fix this in the core code. However, we also > need to preserve the original memory type from vma->vm_page_prot and I > don't think we have any generic macros to just preserve the attributes > but with kernel permissions (pte_mkkernel?). If we fix it in generic_access_phys(), we have to define a macro for all archs that define CONFIG_HAVE_IOREMAP_PROT. x86, loogarch, mips, sh archs only care cacheable attribute of the user prot, so don't involve this issue. But, arc, arm64, powerpc simply copy the user pte prot to the kernel page table. >