Messages in this thread | | | From | Ard Biesheuvel <> | Date | Mon, 10 Oct 2022 13:06:19 +0200 | Subject | Re: [PATCH v2 1/2] ARM: Fix some check warnings of tool sparse |
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On Mon, 10 Oct 2022 at 12:58, Leizhen (ThunderTown) <thunder.leizhen@huawei.com> wrote: > > > > On 2022/10/10 18:20, Ard Biesheuvel wrote: > > On Mon, 10 Oct 2022 at 11:56, Zhen Lei <thunder.leizhen@huawei.com> 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 <thunder.leizhen@huawei.com> > >> --- > >> 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.
> > > >> 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
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