* [PATCH] arm64: mm: explicitly use kernel pte for ioremap_prot()
@ 2026-01-23 3:02 Jinjiang Tu
2026-01-23 18:36 ` Catalin Marinas
0 siblings, 1 reply; 3+ messages in thread
From: Jinjiang Tu @ 2026-01-23 3:02 UTC (permalink / raw)
To: akpm, david, catalin.marinas, will, zengheng4, tujinjiang,
ryan.roberts, anshuman.khandual, wangkefeng.wang,
linux-arm-kernel, linux-mm
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, 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 <zengheng4@huawei.com>
Signed-off-by: Jinjiang Tu <tujinjiang@huawei.com>
---
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.
--
2.43.0
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] arm64: mm: explicitly use kernel pte for ioremap_prot()
2026-01-23 3:02 [PATCH] arm64: mm: explicitly use kernel pte for ioremap_prot() Jinjiang Tu
@ 2026-01-23 18:36 ` Catalin Marinas
2026-01-26 2:25 ` Jinjiang Tu
0 siblings, 1 reply; 3+ messages in thread
From: Catalin Marinas @ 2026-01-23 18:36 UTC (permalink / raw)
To: Jinjiang Tu
Cc: akpm, david, will, zengheng4, ryan.roberts, anshuman.khandual,
wangkefeng.wang, linux-arm-kernel, linux-mm
On Fri, Jan 23, 2026 at 11:02:38AM +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, 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 <zengheng4@huawei.com>
> Signed-off-by: Jinjiang Tu <tujinjiang@huawei.com>
> ---
> 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?).
--
Catalin
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] arm64: mm: explicitly use kernel pte for ioremap_prot()
2026-01-23 18:36 ` Catalin Marinas
@ 2026-01-26 2:25 ` Jinjiang Tu
0 siblings, 0 replies; 3+ messages in thread
From: Jinjiang Tu @ 2026-01-26 2:25 UTC (permalink / raw)
To: Catalin Marinas
Cc: akpm, david, will, zengheng4, ryan.roberts, anshuman.khandual,
wangkefeng.wang, linux-arm-kernel, linux-mm
在 2026/1/24 2:36, Catalin Marinas 写道:
> On Fri, Jan 23, 2026 at 11:02:38AM +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, 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 <zengheng4@huawei.com>
>> Signed-off-by: Jinjiang Tu <tujinjiang@huawei.com>
>> ---
>> 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.
>
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2026-01-26 2:25 UTC | newest]
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2026-01-23 3:02 [PATCH] arm64: mm: explicitly use kernel pte for ioremap_prot() Jinjiang Tu
2026-01-23 18:36 ` Catalin Marinas
2026-01-26 2:25 ` Jinjiang Tu
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