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Re: [PATCH v3] arm64: mm: fix pass user prot to ioremap_prot in generic_access_phys To: Catalin Marinas 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: kwepems200001.china.huawei.com (7.221.188.67) To kwepemr500001.china.huawei.com (7.202.194.229) X-Rspamd-Server: rspam12 X-Stat-Signature: e5zj39etjcejdaohoqthd87p3bb8m35x X-Rspamd-Queue-Id: 8E8E08000B X-Rspam-User: X-HE-Tag: 1769818037-21227 X-HE-Meta: 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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/$pid/environ, generic_access_phys() is called to access the region, >> which triggers a PAN permission-check fault and causes a kernel access >> fault. >> >> The root cause is that generic_access_phys() passes a user pte to >> ioremap_prot(), the user pte sets PTE_USER and PTE_NG bits. Consequently, >> any subsequent kernel-mode access to the remapped address raises a fault. >> >> To fix it, define arch_mk_kernel_prot() to convert user prot to kernel >> prot for arm64, and call arch_mk_kernel_prot() in generic_access_phys(), >> so that a user prot is passed to ioremap_prot(). >> >> Fixes: 893dea9ccd08 ("arm64: Add HAVE_IOREMAP_PROT support") >> Signed-off-by: Zeng Heng >> Signed-off-by: Jinjiang Tu > Reviewed-by: Catalin Marinas > > That's not urgent for 6.19, it's just misuse of /dev/mem (aren't they > all) but it's worth fixing. This issue can be reproduced too with: 1) open and mmap a device that implements generic_access_phys as vm_operations_struct.acess callback. 2) acess the device by ptrace or /proc/$pid/mem. But it's for debug only. So I agree this fix isn't urgent. > Thanks. >