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Message-ID: <300ba40f-4dce-44f1-8809-5a0abcb41aa4@rivosinc.com>
Date: Mon, 27 Nov 2023 13:46:31 +0100
From: Clément Léger <cleger@...osinc.com>
To: Ben Dooks <ben.dooks@...ethink.co.uk>,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc: Christoph Hellwig <hch@...radead.org>,
kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v2] riscv: fix incorrect use of __user pointer
On 27/11/2023 13:02, Ben Dooks wrote:
> On 24/11/2023 11:38, Clément Léger wrote:
>> These warnings were reported by sparse and were due to lack of __user
>> annotation as well as dereferencing such pointer:
>>
>> arch/riscv/kernel/traps_misaligned.c:361:21: warning: dereference of
>> noderef expression
>> arch/riscv/kernel/traps_misaligned.c:373:21: warning: dereference of
>> noderef expression
>> arch/riscv/kernel/traps_misaligned.c:381:21: warning: dereference of
>> noderef expression
>> arch/riscv/kernel/traps_misaligned.c:322:24: warning: incorrect type
>> in initializer (different address spaces)
>> arch/riscv/kernel/traps_misaligned.c:322:24: expected unsigned char
>> const [noderef] __user *__gu_ptr
>> arch/riscv/kernel/traps_misaligned.c:322:24: got unsigned char
>> const [usertype] *addr
>> arch/riscv/kernel/traps_misaligned.c:361:21: warning: dereference of
>> noderef expression
>> arch/riscv/kernel/traps_misaligned.c:373:21: warning: dereference of
>> noderef expression
>> arch/riscv/kernel/traps_misaligned.c:381:21: warning: dereference of
>> noderef expression
>> arch/riscv/kernel/traps_misaligned.c:332:24: warning: incorrect type
>> in initializer (different address spaces)
>> arch/riscv/kernel/traps_misaligned.c:332:24: expected unsigned char
>> [noderef] __user *__gu_ptr
>> arch/riscv/kernel/traps_misaligned.c:332:24: got unsigned char
>> [usertype] *addr
>>
>> As suggested by Christoph Hellwig, casting pointers from an address
>> space to another is not a good idea and we should rather cast the
>> untyped unsigned long to their final address space. Fix the ones in
>> load_u8()/store_u8()/__read_insn() by passing a unsigned long and then
>> casting it to the appropriate type (__user of not) depending if used in
>> kernel/ user mode. Also remove unneeded else construct in store_u8()/
>> load_u8().
>>
>> Reported-by: kernel test robot <lkp@...el.com>
>> Closes:
>> https://lore.kernel.org/oe-kbuild-all/202311160606.obGOOwB3-lkp@intel.com/
>> Signed-off-by: Clément Léger <cleger@...osinc.com>
>> ---
>> arch/riscv/kernel/traps_misaligned.c | 55 +++++++++++++---------------
>> 1 file changed, 25 insertions(+), 30 deletions(-)
>>
>> diff --git a/arch/riscv/kernel/traps_misaligned.c
>> b/arch/riscv/kernel/traps_misaligned.c
>> index 5eba37147caa..a92b88af855a 100644
>> --- a/arch/riscv/kernel/traps_misaligned.c
>> +++ b/arch/riscv/kernel/traps_misaligned.c
>> @@ -265,19 +265,19 @@ static unsigned long get_f32_rs(unsigned long
>> insn, u8 fp_reg_offset,
>> #define GET_F32_RS2S(insn, regs) (get_f32_rs(RVC_RS2S(insn), 0, regs))
>> #ifdef CONFIG_RISCV_M_MODE
>> -static inline int load_u8(struct pt_regs *regs, const u8 *addr, u8
>> *r_val)
>> +static inline int load_u8(struct pt_regs *regs, const unsigned long
>> addr, u8 *r_val)
>> {
>> u8 val;
>> - asm volatile("lbu %0, %1" : "=&r" (val) : "m" (*addr));
>> + asm volatile("lbu %0, %1" : "=&r" (val) : "m" (*(const u8 *)addr));
>> *r_val = val;
>> return 0;
>> }
>> -static inline int store_u8(struct pt_regs *regs, u8 *addr, u8 val)
>> +static inline int store_u8(struct pt_regs *regs, unsigned long addr,
>> u8 val)
>> {
>> - asm volatile ("sb %0, %1\n" : : "r" (val), "m" (*addr));
>> + asm volatile ("sb %0, %1\n" : : "r" (val), "m" (*(u8 *)addr));
>> return 0;
>> }
>> @@ -316,34 +316,32 @@ static inline int get_insn(struct pt_regs *regs,
>> ulong mepc, ulong *r_insn)
>> return 0;
>> }
>> #else
>> -static inline int load_u8(struct pt_regs *regs, const u8 *addr, u8
>> *r_val)
>> +static inline int load_u8(struct pt_regs *regs, const unsigned long
>> addr, u8 *r_val)
>> {
>> - if (user_mode(regs)) {
>> - return __get_user(*r_val, addr);
>> - } else {
>> - *r_val = *addr;
>> - return 0;
>> - }
>> + if (user_mode(regs))
>> + return __get_user(*r_val, (u8 __user *)addr);
>> +
>> + *r_val = *(const u8 *)addr;
>> + return 0;
>> }
>> -static inline int store_u8(struct pt_regs *regs, u8 *addr, u8 val)
>> +static inline int store_u8(struct pt_regs *regs, unsigned long addr,
>> u8 val)
>> {
>> - if (user_mode(regs)) {
>> - return __put_user(val, addr);
>> - } else {
>> - *addr = val;
>> - return 0;
>> - }
>> + if (user_mode(regs))
>> + return __put_user(val, (u8 __user *)addr);
>> +
>> + *(u8 *)addr = val;
>> + return 0;
>> }
>> -#define __read_insn(regs, insn, insn_addr) \
>> +#define __read_insn(regs, insn, insn_addr, type) \
>> ({ \
>> int __ret; \
>> \
>> if (user_mode(regs)) { \
>> - __ret = __get_user(insn, insn_addr); \
>> + __ret = __get_user(insn, (type __user *) insn_addr); \
>> } else { \
>> - insn = *insn_addr; \
>> + insn = *(type *)insn_addr; \
>> __ret = 0; \
>> } \
>> \
>> @@ -356,9 +354,8 @@ static inline int get_insn(struct pt_regs *regs,
>> ulong epc, ulong *r_insn)
>> if (epc & 0x2) {
>> ulong tmp = 0;
>> - u16 __user *insn_addr = (u16 __user *)epc;
>> - if (__read_insn(regs, insn, insn_addr))
>> + if (__read_insn(regs, insn, epc, u16))
>> return -EFAULT;
>> /* __get_user() uses regular "lw" which sign extend the loaded
>> * value make sure to clear higher order bits in case we
>> "or" it
>> @@ -369,16 +366,14 @@ static inline int get_insn(struct pt_regs *regs,
>> ulong epc, ulong *r_insn)
>> *r_insn = insn;
>> return 0;
>> }
>> - insn_addr++;
>> - if (__read_insn(regs, tmp, insn_addr))
>> + epc += sizeof(u16);
>> + if (__read_insn(regs, tmp, epc, u16))
>> return -EFAULT;
>> *r_insn = (tmp << 16) | insn;
>> return 0;
>> } else {
>> - u32 __user *insn_addr = (u32 __user *)epc;
>> -
>> - if (__read_insn(regs, insn, insn_addr))
>> + if (__read_insn(regs, insn, epc, u32))
>> return -EFAULT;
>> if ((insn & __INSN_LENGTH_MASK) == __INSN_LENGTH_32) {
>> *r_insn = insn;
>> @@ -491,7 +486,7 @@ int handle_misaligned_load(struct pt_regs *regs)
>> val.data_u64 = 0;
>> for (i = 0; i < len; i++) {
>> - if (load_u8(regs, (void *)(addr + i), &val.data_bytes[i]))
>> + if (load_u8(regs, addr + i, &val.data_bytes[i]))
>> return -1;
>> }
>> @@ -589,7 +584,7 @@ int handle_misaligned_store(struct pt_regs *regs)
>> return -EOPNOTSUPP;
>> for (i = 0; i < len; i++) {
>> - if (store_u8(regs, (void *)(addr + i), val.data_bytes[i]))
>> + if (store_u8(regs, addr + i, val.data_bytes[i]))
>>
>
> Would it not be easier to have a switch here for memcpy or copy_to_user?
Most probably yes. I'll update the V3 with these modifications. We'll
get rid of store_u8()/load_u8() entirely.
Thanks,
Clément
>
> return -1;
>> }
>>
>
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