[PATCH 4.19 072/190] powerpc/pkeys: Fix handling of pkey state across fork()

Greg Kroah-Hartman
2019-09-13T13:15:27Z

[ Upstream commit 2cd4bd192ee94848695c1c052d87913260e10f36 ]

Protection key tracking information is not copied over to the
mm_struct of the child during fork(). This can cause the child to
erroneously allocate keys that were already allocated. Any allocated
execute-only key is lost aswell.

Add code; called by dup_mmap(), to copy the pkey state from parent to
child explicitly.

This problem was originally found by Dave Hansen on x86, which turns
out to be a problem on powerpc aswell.

Fixes: cf43d3b26452 ("powerpc: Enable pkey subsystem")
Cc: stable@vger.kernel.org # v4.16+
Reviewed-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/powerpc/include/asm/mmu_context.h | 15 +++++++++------
arch/powerpc/mm/pkeys.c | 10 ++++++++++
2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
index b694d6af11508..ae953958c0f33 100644
--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h
@@ -217,12 +217,6 @@ static inline void enter_lazy_tlb(struct mm_struct *mm,
#endif
}

-static inline int arch_dup_mmap(struct mm_struct *oldmm,
- struct mm_struct *mm)
-{
- return 0;
-}
-
#ifndef CONFIG_PPC_BOOK3S_64
static inline void arch_exit_mmap(struct mm_struct *mm)
{
@@ -247,6 +241,7 @@ static inline void arch_bprm_mm_init(struct mm_struct *mm,
#ifdef CONFIG_PPC_MEM_KEYS
bool arch_vma_access_permitted(struct vm_area_struct *vma, bool write,
bool execute, bool foreign);
+void arch_dup_pkeys(struct mm_struct *oldmm, struct mm_struct *mm);
#else /* CONFIG_PPC_MEM_KEYS */
static inline bool arch_vma_access_permitted(struct vm_area_struct *vma,
bool write, bool execute, bool foreign)
@@ -259,6 +254,7 @@ static inline bool arch_vma_access_permitted(struct vm_area_struct *vma,
#define thread_pkey_regs_save(thread)
#define thread_pkey_regs_restore(new_thread, old_thread)
#define thread_pkey_regs_init(thread)
+#define arch_dup_pkeys(oldmm, mm)

static inline u64 pte_to_hpte_pkey_bits(u64 pteflags)
{
@@ -267,5 +263,12 @@ static inline u64 pte_to_hpte_pkey_bits(u64 pteflags)

#endif /* CONFIG_PPC_MEM_KEYS */

+static inline int arch_dup_mmap(struct mm_struct *oldmm,
+ struct mm_struct *mm)
+{
+ arch_dup_pkeys(oldmm, mm);
+ return 0;
+}
+
#endif /* __KERNEL__ */
#endif /* __ASM_POWERPC_MMU_CONTEXT_H */
diff --git a/arch/powerpc/mm/pkeys.c b/arch/powerpc/mm/pkeys.c
index b271b283c785e..25a8dd9cd71db 100644
--- a/arch/powerpc/mm/pkeys.c
+++ b/arch/powerpc/mm/pkeys.c
@@ -414,3 +414,13 @@ bool arch_vma_access_permitted(struct vm_area_struct *vma, bool write,

return pkey_access_permitted(vma_pkey(vma), write, execute);
}
+
+void arch_dup_pkeys(struct mm_struct *oldmm, struct mm_struct *mm)
+{
+ if (static_branch_likely(&pkey_disabled))
+ return;
+
+ /* Duplicate the oldmm pkey state in mm: */
+ mm_pkey_allocation_map(mm) = mm_pkey_allocation_map(oldmm);
+ mm->context.execute_only_pkey = oldmm->context.execute_only_pkey;
+}
--
2.20.1