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arm64: io: Extract user memory type in ioremap_prot() 

The only caller of ioremap_prot() outside of the generic ioremap()
implementation is generic_access_phys(), which passes a 'pgprot_t' value
determined from the user mapping of the target 'pfn' being accessed by
the kernel. On arm64, the 'pgprot_t' contains all of the non-address
bits from the pte, including the permission controls, and so we end up
returning a new user mapping from ioremap_prot() which faults when
accessed from the kernel on systems with PAN:

  | Unable to handle kernel read from unreadable memory at virtual address ffff80008ea89000
  | ...
  | 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

Extract only the memory type from the user 'pgprot_t' in ioremap_prot()
and assert that we're being passed a user mapping, to protect us against
any changes in future that may require additional handling. To avoid
falsely flagging users of ioremap(), provide our own ioremap() macro
which simply wraps __ioremap_prot().

Cc: Zeng Heng <zengheng4@huawei.com>
Cc: Jinjiang Tu <tujinjiang@huawei.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Fixes: 893dea9ccd ("arm64: Add HAVE_IOREMAP_PROT support")
Reported-by: Jinjiang Tu <tujinjiang@huawei.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
master
Will Deacon 2026-02-23 22:10:11 +00:00
parent f6bf47ab32
commit 8f09803713
1 changed files with 15 additions and 2 deletions
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17
arch/arm64/include/asm/io.h
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@ -266,10 +266,23 @@ typedef int (*ioremap_prot_hook_t)(phys_addr_t phys_addr, size_t size,
int arm64_ioremap_prot_hook_register(const ioremap_prot_hook_t hook);
void __iomem *__ioremap_prot(phys_addr_t phys, size_t size, pgprot_t prot);
#define ioremap_prot __ioremap_prot
static inline void __iomem *ioremap_prot(phys_addr_t phys, size_t size,
pgprot_t user_prot)
{
pgprot_t prot;
ptdesc_t user_prot_val = pgprot_val(user_prot);
#define _PAGE_IOREMAP PROT_DEVICE_nGnRE
if (WARN_ON_ONCE(!(user_prot_val & PTE_USER)))
return NULL;
prot = __pgprot_modify(PAGE_KERNEL, PTE_ATTRINDX_MASK,
user_prot_val & PTE_ATTRINDX_MASK);
return __ioremap_prot(phys, size, prot);
}
#define ioremap_prot ioremap_prot
#define ioremap(addr, size) \
__ioremap_prot((addr), (size), __pgprot(PROT_DEVICE_nGnRE))
#define ioremap_wc(addr, size) \
__ioremap_prot((addr), (size), __pgprot(PROT_NORMAL_NC))
#define ioremap_np(addr, size) \