diff options
| author | Dave Hansen <dave.hansen@linux.intel.com> | 2020-01-22 08:53:46 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-10-01 13:12:35 +0200 |
| commit | 6c71f82c25ac40b386a9e6a97bf2e94aa36e9eb4 (patch) | |
| tree | 0125e7a1551bb7abb22e7266069b79d7a558949a /arch | |
| parent | 95b2fe652ca2508b77a1979e53771f01db885880 (diff) | |
x86/pkeys: Add check for pkey "overflow"
[ Upstream commit 16171bffc829272d5e6014bad48f680cb50943d9 ]
Alex Shi reported the pkey macros above arch_set_user_pkey_access()
to be unused. They are unused, and even refer to a nonexistent
CONFIG option.
But, they might have served a good use, which was to ensure that
the code does not try to set values that would not fit in the
PKRU register. As it stands, a too-large 'pkey' value would
be likely to silently overflow the u32 new_pkru_bits.
Add a check to look for overflows. Also add a comment to remind
any future developer to closely examine the types used to store
pkey values if arch_max_pkey() ever changes.
This boots and passes the x86 pkey selftests.
Reported-by: Alex Shi <alex.shi@linux.alibaba.com>
Signed-off-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200122165346.AD4DA150@viggo.jf.intel.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/include/asm/pkeys.h | 5 | ||||
| -rw-r--r-- | arch/x86/kernel/fpu/xstate.c | 9 |
2 files changed, 12 insertions, 2 deletions
diff --git a/arch/x86/include/asm/pkeys.h b/arch/x86/include/asm/pkeys.h index 851c04b7a092..1572a436bc08 100644 --- a/arch/x86/include/asm/pkeys.h +++ b/arch/x86/include/asm/pkeys.h @@ -4,6 +4,11 @@ #define ARCH_DEFAULT_PKEY 0 +/* + * If more than 16 keys are ever supported, a thorough audit + * will be necessary to ensure that the types that store key + * numbers and masks have sufficient capacity. + */ #define arch_max_pkey() (boot_cpu_has(X86_FEATURE_OSPKE) ? 16 : 1) extern int arch_set_user_pkey_access(struct task_struct *tsk, int pkey, diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index 4b900035f220..601a5da1d196 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -907,8 +907,6 @@ const void *get_xsave_field_ptr(int xsave_state) #ifdef CONFIG_ARCH_HAS_PKEYS -#define NR_VALID_PKRU_BITS (CONFIG_NR_PROTECTION_KEYS * 2) -#define PKRU_VALID_MASK (NR_VALID_PKRU_BITS - 1) /* * This will go out and modify PKRU register to set the access * rights for @pkey to @init_val. @@ -927,6 +925,13 @@ int arch_set_user_pkey_access(struct task_struct *tsk, int pkey, if (!boot_cpu_has(X86_FEATURE_OSPKE)) return -EINVAL; + /* + * This code should only be called with valid 'pkey' + * values originating from in-kernel users. Complain + * if a bad value is observed. + */ + WARN_ON_ONCE(pkey >= arch_max_pkey()); + /* Set the bits we need in PKRU: */ if (init_val & PKEY_DISABLE_ACCESS) new_pkru_bits |= PKRU_AD_BIT; |