[PATCH 05/23] m68k: allow pte_offset_map[_lock]() to fail

Hugh Dickins
2023-05-10T04:48:28Z

In rare transient cases, not yet made possible, pte_offset_map() and
pte_offset_map_lock() may not find a page table: handle appropriately.

Restructure cf_tlb_miss() with a pte_unmap() (previously omitted)
at label out, followed by one local_irq_restore() for all.

Signed-off-by: Hugh Dickins <hughd@google.com>
---
arch/m68k/include/asm/mmu_context.h | 6 ++--
arch/m68k/kernel/sys_m68k.c | 2 ++
arch/m68k/mm/mcfmmu.c | 52 ++++++++++++-----------------
3 files changed, 27 insertions(+), 33 deletions(-)

diff --git a/arch/m68k/include/asm/mmu_context.h b/arch/m68k/include/asm/mmu_context.h
index 8ed6ac14d99f..141bbdfad960 100644
--- a/arch/m68k/include/asm/mmu_context.h
+++ b/arch/m68k/include/asm/mmu_context.h
@@ -99,7 +99,7 @@ static inline void load_ksp_mmu(struct task_struct *task)
p4d_t *p4d;
pud_t *pud;
pmd_t *pmd;
- pte_t *pte;
+ pte_t *pte = NULL;
unsigned long mmuar;

local_irq_save(flags);
@@ -139,7 +139,7 @@ static inline void load_ksp_mmu(struct task_struct *task)

pte = (mmuar >= PAGE_OFFSET) ? pte_offset_kernel(pmd, mmuar)
: pte_offset_map(pmd, mmuar);
- if (pte_none(*pte) || !pte_present(*pte))
+ if (!pte || pte_none(*pte) || !pte_present(*pte))
goto bug;

set_pte(pte, pte_mkyoung(*pte));
@@ -161,6 +161,8 @@ static inline void load_ksp_mmu(struct task_struct *task)
bug:
pr_info("ksp load failed: mm=0x%p ksp=0x08%lx\n", mm, mmuar);
end:
+ if (pte && mmuar < PAGE_OFFSET)
+ pte_unmap(pte);
local_irq_restore(flags);
}

diff --git a/arch/m68k/kernel/sys_m68k.c b/arch/m68k/kernel/sys_m68k.c
index bd0274c7592e..c586034d2a7a 100644
--- a/arch/m68k/kernel/sys_m68k.c
+++ b/arch/m68k/kernel/sys_m68k.c
@@ -488,6 +488,8 @@ sys_atomic_cmpxchg_32(unsigned long newval, int oldval, int d3, int d4, int d5,
if (!pmd_present(*pmd))
goto bad_access;
pte = pte_offset_map_lock(mm, pmd, (unsigned long)mem, &ptl);
+ if (!pte)
+ goto bad_access;
if (!pte_present(*pte) || !pte_dirty(*pte)
|| !pte_write(*pte)) {
pte_unmap_unlock(pte, ptl);
diff --git a/arch/m68k/mm/mcfmmu.c b/arch/m68k/mm/mcfmmu.c
index 70aa0979e027..42f45abea37a 100644
--- a/arch/m68k/mm/mcfmmu.c
+++ b/arch/m68k/mm/mcfmmu.c
@@ -91,7 +91,8 @@ int cf_tlb_miss(struct pt_regs *regs, int write, int dtlb, int extension_word)
p4d_t *p4d;
pud_t *pud;
pmd_t *pmd;
- pte_t *pte;
+ pte_t *pte = NULL;
+ int ret = -1;
int asid;

local_irq_save(flags);
@@ -100,47 +101,33 @@ int cf_tlb_miss(struct pt_regs *regs, int write, int dtlb, int extension_word)
regs->pc + (extension_word * sizeof(long));

mm = (!user_mode(regs) && KMAPAREA(mmuar)) ? &init_mm : current->mm;
- if (!mm) {
- local_irq_restore(flags);
- return -1;
- }
+ if (!mm)
+ goto out;

pgd = pgd_offset(mm, mmuar);
- if (pgd_none(*pgd)) {
- local_irq_restore(flags);
- return -1;
- }
+ if (pgd_none(*pgd))
+ goto out;

p4d = p4d_offset(pgd, mmuar);
- if (p4d_none(*p4d)) {
- local_irq_restore(flags);
- return -1;
- }
+ if (p4d_none(*p4d))
+ goto out;

pud = pud_offset(p4d, mmuar);
- if (pud_none(*pud)) {
- local_irq_restore(flags);
- return -1;
- }
+ if (pud_none(*pud))
+ goto out;

pmd = pmd_offset(pud, mmuar);
- if (pmd_none(*pmd)) {
- local_irq_restore(flags);
- return -1;
- }
+ if (pmd_none(*pmd))
+ goto out;

pte = (KMAPAREA(mmuar)) ? pte_offset_kernel(pmd, mmuar)
: pte_offset_map(pmd, mmuar);
- if (pte_none(*pte) || !pte_present(*pte)) {
- local_irq_restore(flags);
- return -1;
- }
+ if (!pte || pte_none(*pte) || !pte_present(*pte))
+ goto out;

if (write) {
- if (!pte_write(*pte)) {
- local_irq_restore(flags);
- return -1;
- }
+ if (!pte_write(*pte))
+ goto out;
set_pte(pte, pte_mkdirty(*pte));
}

@@ -161,9 +148,12 @@ int cf_tlb_miss(struct pt_regs *regs, int write, int dtlb, int extension_word)
mmu_write(MMUOR, MMUOR_ACC | MMUOR_UAA);
else
mmu_write(MMUOR, MMUOR_ITLB | MMUOR_ACC | MMUOR_UAA);
-
+ ret = 0;
+out:
+ if (pte && !KMAPAREA(mmuar))
+ pte_unmap(pte);
local_irq_restore(flags);
- return 0;
+ return ret;
}

void __init cf_bootmem_alloc(void)
--
2.35.3