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 <rus...@russell.cc>
Fixes: b11931e9adc1 ("powerpc/64s: add pte_needs_flush and
huge_pmd_needs_flush")
Signed-off-by: Benjamin Gray <bg...@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(-)
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));
base-commit: 90dbf76e470bc4b973052a8f26ea43bae30f9aec
--
2.39.2
