| Message ID | 20230302225947.81083-1-bgray@linux.ibm.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 1abce0580b89464546ae06abd5891ebec43c9470 |
| Headers | show |
| Series | [v2] powerpc/64s: Fix __pte_needs_flush() false positive warning | expand |
On Fri, 03 Mar 2023 09:59:47 +1100, Benjamin Gray wrote: > Userspace PROT_NONE ptes set _PAGE_PRIVILEGED, triggering a false > positive debug assertion that __pte_flags_need_flush() is not called > on a kernel mapping. > > Detect when it is a userspace PROT_NONE page by checking the required > bits of PAGE_NONE are set, and none of the RWX bits are set. > pte_protnone() is insufficient here because it always returns 0 when > CONFIG_NUMA_BALANCING=n. > > [...] Applied to powerpc/fixes. [1/1] powerpc/64s: Fix __pte_needs_flush() false positive warning https://git.kernel.org/powerpc/c/1abce0580b89464546ae06abd5891ebec43c9470 cheers
diff --git a/arch/powerpc/include/asm/book3s/64/tlbflush.h b/arch/powerpc/include/asm/book3s/64/tlbflush.h index 2bbc0fcce04a..5e26c7f2c25a 100644 --- a/arch/powerpc/include/asm/book3s/64/tlbflush.h +++ b/arch/powerpc/include/asm/book3s/64/tlbflush.h @@ -148,6 +148,11 @@ static inline void flush_tlb_fix_spurious_fault(struct vm_area_struct *vma, */ } +static inline bool __pte_protnone(unsigned long pte) +{ + return (pte & (pgprot_val(PAGE_NONE) | _PAGE_RWX)) == pgprot_val(PAGE_NONE); +} + static inline bool __pte_flags_need_flush(unsigned long oldval, unsigned long newval) { @@ -164,8 +169,8 @@ static inline bool __pte_flags_need_flush(unsigned long oldval, /* * We do not expect kernel mappings or non-PTEs or not-present PTEs. */ - VM_WARN_ON_ONCE(oldval & _PAGE_PRIVILEGED); - VM_WARN_ON_ONCE(newval & _PAGE_PRIVILEGED); + VM_WARN_ON_ONCE(!__pte_protnone(oldval) && oldval & _PAGE_PRIVILEGED); + VM_WARN_ON_ONCE(!__pte_protnone(newval) && newval & _PAGE_PRIVILEGED); VM_WARN_ON_ONCE(!(oldval & _PAGE_PTE)); VM_WARN_ON_ONCE(!(newval & _PAGE_PTE)); VM_WARN_ON_ONCE(!(oldval & _PAGE_PRESENT));
Userspace PROT_NONE ptes set _PAGE_PRIVILEGED, triggering a false positive debug assertion that __pte_flags_need_flush() is not called on a kernel mapping. Detect when it is a userspace PROT_NONE page by checking the required bits of PAGE_NONE are set, and none of the RWX bits are set. pte_protnone() is insufficient here because it always returns 0 when CONFIG_NUMA_BALANCING=n. Reported-by: Russell Currey <ruscur@russell.cc> Fixes: b11931e9adc1 ("powerpc/64s: add pte_needs_flush and huge_pmd_needs_flush") Signed-off-by: Benjamin Gray <bgray@linux.ibm.com> --- v2: removed an auto-import that slipped in MRE (CONFIG_DEBUG_VM must be enabled): int main(int argc, char **argv) { char *buf = mmap(NULL, getpagesize(), PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0); buf[0] = '1'; mprotect(buf, getpagesize(), PROT_NONE); return 0; } --- arch/powerpc/include/asm/book3s/64/tlbflush.h | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) base-commit: 90dbf76e470bc4b973052a8f26ea43bae30f9aec