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Tue, 11 Oct 2022 10:30:10 +0800 Subject: Re: [PATCH v2 1/2] ARM: Fix some check warnings of tool sparse To: Ard Biesheuvel CC: Russell King , , References: <20221010095346.1957-1-thunder.leizhen@huawei.com> <20221010095346.1957-2-thunder.leizhen@huawei.com> <1ab4c651-f0ab-1107-1784-ad255dabc33a@huawei.com> From: "Leizhen (ThunderTown)" Message-ID: Date: Tue, 11 Oct 2022 10:29:58 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-Originating-IP: [10.174.178.55] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpemm500006.china.huawei.com (7.185.36.236) X-CFilter-Loop: Reflected X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221010_193013_168055_6614E0DE X-CRM114-Status: GOOD ( 21.11 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2022/10/10 19:06, Ard Biesheuvel wrote: > On Mon, 10 Oct 2022 at 12:58, Leizhen (ThunderTown) > wrote: >> >> >> >> On 2022/10/10 18:20, Ard Biesheuvel wrote: >>> On Mon, 10 Oct 2022 at 11:56, Zhen Lei wrote: >>>> >>>> Fix the following warnings: >>>> warning: incorrect type in initializer (different address spaces) >>>> expected unsigned short [noderef] __user *register __p >>>> got unsigned short [usertype] * >>>> warning: cast removes address space '__user' of expression >>>> >>>> Signed-off-by: Zhen Lei >>>> --- >>>> arch/arm/kernel/traps.c | 10 +++++----- >>>> 1 file changed, 5 insertions(+), 5 deletions(-) >>>> >>>> diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c >>>> index 20b2db6dcd1ced7..34aa80c09c508c1 100644 >>>> --- a/arch/arm/kernel/traps.c >>>> +++ b/arch/arm/kernel/traps.c >>>> @@ -188,9 +188,9 @@ static void dump_instr(const char *lvl, struct pt_regs *regs) >>>> } >>>> } else { >>>> if (thumb) >>>> - bad = get_user(val, &((u16 *)addr)[i]); >>>> + bad = get_user(val, &((u16 __user *)addr)[i]); >>>> else >>>> - bad = get_user(val, &((u32 *)addr)[i]); >>>> + bad = get_user(val, &((u32 __user *)addr)[i]); >>>> } >>>> >>>> if (!bad) >>>> @@ -455,15 +455,15 @@ asmlinkage void do_undefinstr(struct pt_regs *regs) >>>> if (processor_mode(regs) == SVC_MODE) { >>>> #ifdef CONFIG_THUMB2_KERNEL >>>> if (thumb_mode(regs)) { >>>> - instr = __mem_to_opcode_thumb16(((u16 *)pc)[0]); >>>> + instr = __mem_to_opcode_thumb16(((__force u16 *)pc)[0]); >>> >>> Shouldn't this be __user as well? (and below) >> >> unsigned int instr; >> void __user *pc; >> >> The __user can clear the warning, but a new warning will be generated. >> >> instr = __mem_to_opcode_thumb16(((u16 *)pc)[0]); >> ^new ^old >> >> arch/arm/kernel/traps.c:473:33: warning: dereference of noderef expression >> > > This is because dereferencing a __user pointer is not permitted. > > So this code should be using get_kernel_nofault() here not a plain > dereference of PC. So better to fix that properly instead of papering > over it with a __force cast just to make sparse happy. How about: @@ -451,9 +451,9 @@ int call_undef_hook(struct pt_regs *regs, unsigned int instr) asmlinkage void do_undefinstr(struct pt_regs *regs) { unsigned int instr; - void __user *pc; + void *pc; - pc = (void __user *)instruction_pointer(regs); + pc = (void *)instruction_pointer(regs); if (processor_mode(regs) == SVC_MODE) { #ifdef CONFIG_THUMB2_KERNEL @@ -497,7 +497,7 @@ asmlinkage void do_undefinstr(struct pt_regs *regs) } #endif arm_notify_die("Oops - undefined instruction", regs, - SIGILL, ILL_ILLOPC, pc, 0, 6); + SIGILL, ILL_ILLOPC, (void __user *)pc, 0, 6); } NOKPROBE_SYMBOL(do_undefinstr) The 'pc' may come from kernel or user. And I found that all the get_user() calls have already done type casts to the pc, except arm_notify_die(). I think the above changes are reasonable. > > >>> >>>> if (is_wide_instruction(instr)) { >>>> u16 inst2; >>>> - inst2 = __mem_to_opcode_thumb16(((u16 *)pc)[1]); >>>> + inst2 = __mem_to_opcode_thumb16(((__force u16 *)pc)[1]); >>>> instr = __opcode_thumb32_compose(instr, inst2); >>>> } >>>> } else >>>> #endif >>>> - instr = __mem_to_opcode_arm(*(u32 *) pc); >>>> + instr = __mem_to_opcode_arm(*(__force u32 *) pc); >>>> } else if (thumb_mode(regs)) { >>>> if (get_user(instr, (u16 __user *)pc)) >>>> goto die_sig; >>>> -- >>>> 2.25.1 >>>> >>>> >>>> _______________________________________________ >>>> linux-arm-kernel mailing list >>>> linux-arm-kernel@lists.infradead.org >>>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >>> . >>> >> >> -- >> Regards, >> Zhen Lei > . > -- Regards, Zhen Lei _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel