On 32-bit book3s with hash-MMUs, tlb_flush() was a no-op. This was unnoticed because all uses until recently were for unmaps, and thus handled by __tlb_remove_tlb_entry().

After commit 4a18419f71cd ("mm/mprotect: use mmu_gather") in kernel 5.19, tlb_gather_mmu() started being used for mprotect as well. This caused mprotect to simply not work on these machines:

int *ptr = mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0); *ptr = 1; // force HPTE to be created mprotect(ptr, 4096, PROT_READ); *ptr = 2; // should segfault, but succeeds

Fixed by making tlb_flush() actually flush TLB pages. This finally agrees with the behaviour of boot3s64's tlb_flush().

Fixes: 4a18419f71cd ("mm/mprotect: use mmu_gather") Cc: stable@vger.kernel.org Reviewed-by: Christophe Leroy christophe.leroy@csgroup.eu Reviewed-by: Ritesh Harjani (IBM) ritesh.list@gmail.com Signed-off-by: Dave Vasilevsky dave@vasilevsky.ca --- Changes in v3: - Fix formatting - Link to v2: https://lore.kernel.org/r/20251111-vasi-mprotect-g3-v2-1-881c94afbc42@vasile...

Changes in v2: - Flush entire TLB if full mm is requested. - Link to v1: https://lore.kernel.org/r/20251027-vasi-mprotect-g3-v1-1-3c5187085f9a@vasile... --- arch/powerpc/include/asm/book3s/32/tlbflush.h | 5 ++++- arch/powerpc/mm/book3s32/tlb.c | 9 +++++++++ 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/book3s/32/tlbflush.h b/arch/powerpc/include/asm/book3s/32/tlbflush.h index e43534da5207aa3b0cb3c07b78e29b833c141f3f..4be2200a3c7e1e8307f5ce1f1d5d28047429c106 100644 --- a/arch/powerpc/include/asm/book3s/32/tlbflush.h +++ b/arch/powerpc/include/asm/book3s/32/tlbflush.h @@ -11,6 +11,7 @@ void hash__flush_tlb_mm(struct mm_struct *mm); void hash__flush_tlb_page(struct vm_area_struct *vma, unsigned long vmaddr); void hash__flush_range(struct mm_struct *mm, unsigned long start, unsigned long end); +void hash__flush_gather(struct mmu_gather *tlb);

#ifdef CONFIG_SMP void _tlbie(unsigned long address); @@ -29,7 +30,9 @@ void _tlbia(void); static inline void tlb_flush(struct mmu_gather *tlb) { /* 603 needs to flush the whole TLB here since it doesn't use a hash table. */ - if (!mmu_has_feature(MMU_FTR_HPTE_TABLE)) + if (mmu_has_feature(MMU_FTR_HPTE_TABLE)) + hash__flush_gather(tlb); + else _tlbia(); }

diff --git a/arch/powerpc/mm/book3s32/tlb.c b/arch/powerpc/mm/book3s32/tlb.c index 9ad6b56bfec96e989b96f027d075ad5812500854..e54a7b0112322e5818d80facd2e3c7722e6dd520 100644 --- a/arch/powerpc/mm/book3s32/tlb.c +++ b/arch/powerpc/mm/book3s32/tlb.c @@ -105,3 +105,12 @@ void hash__flush_tlb_page(struct vm_area_struct *vma, unsigned long vmaddr) flush_hash_pages(mm->context.id, vmaddr, pmd_val(*pmd), 1); } EXPORT_SYMBOL(hash__flush_tlb_page); + +void hash__flush_gather(struct mmu_gather *tlb) +{ + if (tlb->fullmm || tlb->need_flush_all) + hash__flush_tlb_mm(tlb->mm); + else + hash__flush_range(tlb->mm, tlb->start, tlb->end); +} +EXPORT_SYMBOL(hash__flush_gather);

--- base-commit: 24172e0d79900908cf5ebf366600616d29c9b417 change-id: 20251027-vasi-mprotect-g3-f8f5278d4140

Best regards,