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

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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: cf43d3b264 ("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>
This commit is contained in:
Ram Pai 2018-12-20 12:03:30 -08:00 committed by Michael Ellerman
parent 2f07229f02
commit 2cd4bd192e
2 changed files with 19 additions and 6 deletions
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15
arch/powerpc/include/asm/mmu_context.h
View File

@ -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;
}
#ifdef CONFIG_PPC_BOOK3E_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 */

10
arch/powerpc/mm/pkeys.c
View File

@ -415,3 +415,13 @@ 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;
}