58ab9a088d
Kirill reported a warning from UBSAN about undefined behavior when using protection keys. He is running on hardware that actually has support for it, which is not widely available. The warning triggers because of very large shifts of integers when doing a pkey_free() of a large, invalid value. This happens because we never check that the pkey "fits" into the mm_pkey_allocation_map(). I do not believe there is any danger here of anything bad happening other than some aliasing issues where somebody could do: pkey_free(35); and the kernel would effectively execute: pkey_free(8); While this might be confusing to an app that was doing something stupid, it has to do something stupid and the effects are limited to the app shooting itself in the foot. Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Cc: stable@vger.kernel.org Cc: linux-kselftest@vger.kernel.org Cc: shuah@kernel.org Cc: kirill.shutemov@linux.intel.com Link: http://lkml.kernel.org/r/20170223222603.A022ED65@viggo.jf.intel.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
109 lines
2.7 KiB
C
109 lines
2.7 KiB
C
#ifndef _ASM_X86_PKEYS_H
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#define _ASM_X86_PKEYS_H
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#define arch_max_pkey() (boot_cpu_has(X86_FEATURE_OSPKE) ? 16 : 1)
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extern int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
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unsigned long init_val);
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/*
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* Try to dedicate one of the protection keys to be used as an
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* execute-only protection key.
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*/
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extern int __execute_only_pkey(struct mm_struct *mm);
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static inline int execute_only_pkey(struct mm_struct *mm)
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{
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if (!boot_cpu_has(X86_FEATURE_OSPKE))
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return 0;
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return __execute_only_pkey(mm);
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}
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extern int __arch_override_mprotect_pkey(struct vm_area_struct *vma,
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int prot, int pkey);
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static inline int arch_override_mprotect_pkey(struct vm_area_struct *vma,
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int prot, int pkey)
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{
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if (!boot_cpu_has(X86_FEATURE_OSPKE))
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return 0;
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return __arch_override_mprotect_pkey(vma, prot, pkey);
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}
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extern int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
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unsigned long init_val);
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#define ARCH_VM_PKEY_FLAGS (VM_PKEY_BIT0 | VM_PKEY_BIT1 | VM_PKEY_BIT2 | VM_PKEY_BIT3)
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#define mm_pkey_allocation_map(mm) (mm->context.pkey_allocation_map)
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#define mm_set_pkey_allocated(mm, pkey) do { \
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mm_pkey_allocation_map(mm) |= (1U << pkey); \
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} while (0)
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#define mm_set_pkey_free(mm, pkey) do { \
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mm_pkey_allocation_map(mm) &= ~(1U << pkey); \
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} while (0)
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static inline
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bool mm_pkey_is_allocated(struct mm_struct *mm, int pkey)
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{
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/*
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* "Allocated" pkeys are those that have been returned
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* from pkey_alloc(). pkey 0 is special, and never
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* returned from pkey_alloc().
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*/
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if (pkey <= 0)
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return false;
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if (pkey >= arch_max_pkey())
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return false;
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return mm_pkey_allocation_map(mm) & (1U << pkey);
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}
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/*
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* Returns a positive, 4-bit key on success, or -1 on failure.
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*/
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static inline
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int mm_pkey_alloc(struct mm_struct *mm)
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{
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/*
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* Note: this is the one and only place we make sure
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* that the pkey is valid as far as the hardware is
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* concerned. The rest of the kernel trusts that
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* only good, valid pkeys come out of here.
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*/
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u16 all_pkeys_mask = ((1U << arch_max_pkey()) - 1);
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int ret;
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/*
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* Are we out of pkeys? We must handle this specially
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* because ffz() behavior is undefined if there are no
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* zeros.
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*/
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if (mm_pkey_allocation_map(mm) == all_pkeys_mask)
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return -1;
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ret = ffz(mm_pkey_allocation_map(mm));
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mm_set_pkey_allocated(mm, ret);
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return ret;
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}
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static inline
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int mm_pkey_free(struct mm_struct *mm, int pkey)
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{
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if (!mm_pkey_is_allocated(mm, pkey))
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return -EINVAL;
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mm_set_pkey_free(mm, pkey);
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return 0;
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}
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extern int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
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unsigned long init_val);
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extern int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
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unsigned long init_val);
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extern void copy_init_pkru_to_fpregs(void);
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#endif /*_ASM_X86_PKEYS_H */
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