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Commit cfbf227e authored by Ram Pai's avatar Ram Pai Committed by Greg Kroah-Hartman
Browse files

powerpc/pkeys: Fix handling of pkey state across fork() 



[ 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: cf43d3b2 ("powerpc: Enable pkey subsystem")
Cc: stable@vger.kernel.org # v4.16+
Reviewed-by: default avatarThiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: default avatarRam Pai <linuxram@us.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 2ad95be1

arch/powerpc/include/asm/mmu_context.h

+9 −6
Original line number Diff line number Diff line
@@ -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 */

arch/powerpc/mm/pkeys.c

+10 −0
Original line number Diff line number Diff line
@@ -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;

}