linux-kernel - Re: [PATCH 2/2] riscv: misaligned: fix sleeping function called during misaligned access handling

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Message-ID: <22a2c734-b446-4b1e-a2bc-a0080656fe29@ghiti.fr>
Date: Fri, 11 Apr 2025 10:35:21 +0200
From: Alexandre Ghiti <alex@...ti.fr>
To: Clément Léger <cleger@...osinc.com>,
 Nylon Chen <nylon.chen@...ive.com>, linux-kernel@...r.kernel.org
Cc: linux-riscv@...ts.infradead.org, paul.walmsley@...ive.com,
 palmer@...belt.com, aou@...s.berkeley.edu, charlie@...osinc.com,
 jesse@...osinc.com, evan@...osinc.com, zhangchunyan@...as.ac.cn,
 samuel.holland@...ive.com, zong.li@...ive.com
Subject: Re: [PATCH 2/2] riscv: misaligned: fix sleeping function called
 during misaligned access handling

Hi Clément,

On 11/04/2025 09:36, Clément Léger wrote:
> Hi Nylon,
>
> I already have a pending fix for that bug which is to reenable
> interrupts while handling misaligned faults. Please see:
> https://lore.kernel.org/linux-riscv/20250317170625.1142870-12-cleger@rivosinc.com/

Can you extract this fix from the series so that it can be merged in 6.15?

Thanks,

Alex

>
> Thanks,
>
> Clément
>
> On 11/04/2025 09:38, Nylon Chen wrote:
>> Use copy_from_user_nofault() and copy_to_user_nofault() instead of
>> copy_from/to_user functions in the misaligned access trap handlers.
>>
>> The following bug report was found when executing misaligned memory
>> accesses:
>>
>> BUG: sleeping function called from invalid context at ./include/linux/uaccess.h:162
>> in_atomic(): 0, irqs_disabled(): 1, non_block: 0, pid: 115, name: two
>> preempt_count: 0, expected: 0
>> CPU: 0 UID: 0 PID: 115 Comm: two Not tainted 6.14.0-rc5 #24
>> Hardware name: riscv-virtio,qemu (DT)
>> Call Trace:
>>   [<ffffffff800160ea>] dump_backtrace+0x1c/0x24
>>   [<ffffffff80002304>] show_stack+0x28/0x34
>>   [<ffffffff80010fae>] dump_stack_lvl+0x4a/0x68
>>   [<ffffffff80010fe0>] dump_stack+0x14/0x1c
>>   [<ffffffff8004e44e>] __might_resched+0xfa/0x104
>>   [<ffffffff8004e496>] __might_sleep+0x3e/0x62
>>   [<ffffffff801963c4>] __might_fault+0x1c/0x24
>>   [<ffffffff80425352>] _copy_from_user+0x28/0xaa
>>   [<ffffffff8000296c>] handle_misaligned_store+0x204/0x254
>>   [<ffffffff809eae82>] do_trap_store_misaligned+0x24/0xee
>>   [<ffffffff809f4f1a>] handle_exception+0x146/0x152
>>
>> Fixes: b686ecdeacf6 ("riscv: misaligned: Restrict user access to kernel memory")
>> Fixes: 441381506ba7 ("riscv: misaligned: remove CONFIG_RISCV_M_MODE specific code")
>>
>> Signed-off-by: Zong Li <zong.li@...ive.com>
>> Signed-off-by: Nylon Chen <nylon.chen@...ive.com>
>> ---
>>   arch/riscv/kernel/traps_misaligned.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c
>> index d7275dfb6b7e..563f73f88fa8 100644
>> --- a/arch/riscv/kernel/traps_misaligned.c
>> +++ b/arch/riscv/kernel/traps_misaligned.c
>> @@ -455,7 +455,7 @@ static int handle_scalar_misaligned_load(struct pt_regs *regs)
>>   
>>   	val.data_u64 = 0;
>>   	if (user_mode(regs)) {
>> -		if (copy_from_user(&val, (u8 __user *)addr, len))
>> +		if (copy_from_user_nofault(&val, (u8 __user *)addr, len))
>>   			return -1;
>>   	} else {
>>   		memcpy(&val, (u8 *)addr, len);
>> @@ -556,7 +556,7 @@ static int handle_scalar_misaligned_store(struct pt_regs *regs)
>>   		return -EOPNOTSUPP;
>>   
>>   	if (user_mode(regs)) {
>> -		if (copy_to_user((u8 __user *)addr, &val, len))
>> +		if (copy_to_user_nofault((u8 __user *)addr, &val, len))
>>   			return -1;
>>   	} else {
>>   		memcpy((u8 *)addr, &val, len);
>
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> linux-riscv@...ts.infradead.org
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