* [PATCH] smb: avoid field overflow warning
@ 2023-06-16 9:07 Arnd Bergmann
2023-06-16 14:40 ` Namjae Jeon
0 siblings, 1 reply; 4+ messages in thread
From: Arnd Bergmann @ 2023-06-16 9:07 UTC (permalink / raw)
To: Namjae Jeon, Steve French
Cc: Arnd Bergmann, Sergey Senozhatsky, Tom Talpey, Nathan Chancellor,
Nick Desaulniers, Tom Rix, Christian Brauner, Dave Chinner,
Kees Cook, Mickaël Salaün, Ronnie Sahlberg,
Hyunchul Lee, linux-cifs, linux-kernel, llvm
From: Arnd Bergmann <arnd@arndb.de>
clang warns about a possible field overflow in a memcpy:
In file included from fs/smb/server/smb_common.c:7:
include/linux/fortify-string.h:583:4: error: call to '__write_overflow_field' declared with 'warning' attribute: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror,-Wattribute-warning]
__write_overflow_field(p_size_field, size);
It appears to interpret the "&out[baselen + 4]" as referring to a single
byte of the character array, while the equivalen "out + baselen + 4" is
seen as an offset into the array.
I don't see that kind of warning elsewhere, so just go with the simple
rework.
Fixes: e2f34481b24db ("cifsd: add server-side procedures for SMB3")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
fs/smb/server/smb_common.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/smb/server/smb_common.c b/fs/smb/server/smb_common.c
index a7e81067bc991..e3273fa640b07 100644
--- a/fs/smb/server/smb_common.c
+++ b/fs/smb/server/smb_common.c
@@ -536,7 +536,7 @@ int ksmbd_extract_shortname(struct ksmbd_conn *conn, const char *longname,
out[baselen + 3] = PERIOD;
if (dot_present)
- memcpy(&out[baselen + 4], extension, 4);
+ memcpy(out + baselen + 4, extension, 1);
else
out[baselen + 4] = '\0';
smbConvertToUTF16((__le16 *)shortname, out, PATH_MAX,
--
2.39.2
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] smb: avoid field overflow warning
2023-06-16 9:07 [PATCH] smb: avoid field overflow warning Arnd Bergmann
@ 2023-06-16 14:40 ` Namjae Jeon
2023-06-16 14:42 ` Arnd Bergmann
0 siblings, 1 reply; 4+ messages in thread
From: Namjae Jeon @ 2023-06-16 14:40 UTC (permalink / raw)
To: Arnd Bergmann
Cc: Steve French, Arnd Bergmann, Sergey Senozhatsky, Tom Talpey,
Nathan Chancellor, Nick Desaulniers, Tom Rix, Christian Brauner,
Dave Chinner, Kees Cook, Mickaël Salaün,
Ronnie Sahlberg, Hyunchul Lee, linux-cifs, linux-kernel, llvm
2023-06-16 18:07 GMT+09:00, Arnd Bergmann <arnd@kernel.org>:
> From: Arnd Bergmann <arnd@arndb.de>
Hi Arnd,
>
> clang warns about a possible field overflow in a memcpy:
>
> In file included from fs/smb/server/smb_common.c:7:
> include/linux/fortify-string.h:583:4: error: call to
> '__write_overflow_field' declared with 'warning' attribute: detected write
> beyond size of field (1st parameter); maybe use struct_group()?
> [-Werror,-Wattribute-warning]
> __write_overflow_field(p_size_field, size);
>
> It appears to interpret the "&out[baselen + 4]" as referring to a single
> byte of the character array, while the equivalen "out + baselen + 4" is
> seen as an offset into the array.
>
> I don't see that kind of warning elsewhere, so just go with the simple
> rework.
>
> Fixes: e2f34481b24db ("cifsd: add server-side procedures for SMB3")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> fs/smb/server/smb_common.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/smb/server/smb_common.c b/fs/smb/server/smb_common.c
> index a7e81067bc991..e3273fa640b07 100644
> --- a/fs/smb/server/smb_common.c
> +++ b/fs/smb/server/smb_common.c
> @@ -536,7 +536,7 @@ int ksmbd_extract_shortname(struct ksmbd_conn *conn,
> const char *longname,
> out[baselen + 3] = PERIOD;
>
> if (dot_present)
> - memcpy(&out[baselen + 4], extension, 4);
> + memcpy(out + baselen + 4, extension, 1);
Is there any reason to change copy bytes from 4 bytes to 1 byte?
Thanks!
> else
> out[baselen + 4] = '\0';
> smbConvertToUTF16((__le16 *)shortname, out, PATH_MAX,
> --
> 2.39.2
>
>
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] smb: avoid field overflow warning
2023-06-16 14:40 ` Namjae Jeon
@ 2023-06-16 14:42 ` Arnd Bergmann
2023-06-16 14:49 ` Namjae Jeon
0 siblings, 1 reply; 4+ messages in thread
From: Arnd Bergmann @ 2023-06-16 14:42 UTC (permalink / raw)
To: Namjae Jeon, Arnd Bergmann
Cc: Steve French, Sergey Senozhatsky, Tom Talpey, Nathan Chancellor,
Nick Desaulniers, Tom Rix, Christian Brauner, Dave Chinner,
Kees Cook, Mickaël Salaün, Ronnie Sahlberg,
Hyunchul Lee, linux-cifs, linux-kernel, llvm
On Fri, Jun 16, 2023, at 16:40, Namjae Jeon wrote:
> 2023-06-16 18:07 GMT+09:00, Arnd Bergmann <arnd@kernel.org>:
>> From: Arnd Bergmann <arnd@arndb.de>
>>
>> clang warns about a possible field overflow in a memcpy:
>>
>> In file included from fs/smb/server/smb_common.c:7:
>> include/linux/fortify-string.h:583:4: error: call to
>> '__write_overflow_field' declared with 'warning' attribute: detected write
>> beyond size of field (1st parameter); maybe use struct_group()?
>> [-Werror,-Wattribute-warning]
>> __write_overflow_field(p_size_field, size);
>>
>> It appears to interpret the "&out[baselen + 4]" as referring to a single
>> byte of the character array, while the equivalen "out + baselen + 4" is
>> seen as an offset into the array.
>>
>> I don't see that kind of warning elsewhere, so just go with the simple
>> rework.
>>
>> Fixes: e2f34481b24db ("cifsd: add server-side procedures for SMB3")
>> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>> ---
>> fs/smb/server/smb_common.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/fs/smb/server/smb_common.c b/fs/smb/server/smb_common.c
>> index a7e81067bc991..e3273fa640b07 100644
>> --- a/fs/smb/server/smb_common.c
>> +++ b/fs/smb/server/smb_common.c
>> @@ -536,7 +536,7 @@ int ksmbd_extract_shortname(struct ksmbd_conn *conn,
>> const char *longname,
>> out[baselen + 3] = PERIOD;
>>
>> if (dot_present)
>> - memcpy(&out[baselen + 4], extension, 4);
>> + memcpy(out + baselen + 4, extension, 1);
> Is there any reason to change copy bytes from 4 bytes to 1 byte?
>
No, that was an accident, this patch is wrong.
I have to revisit this one and check if my change actually still works
after I change it back to the correct length.
Arnd
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] smb: avoid field overflow warning
2023-06-16 14:42 ` Arnd Bergmann
@ 2023-06-16 14:49 ` Namjae Jeon
0 siblings, 0 replies; 4+ messages in thread
From: Namjae Jeon @ 2023-06-16 14:49 UTC (permalink / raw)
To: Arnd Bergmann
Cc: Arnd Bergmann, Steve French, Sergey Senozhatsky, Tom Talpey,
Nathan Chancellor, Nick Desaulniers, Tom Rix, Christian Brauner,
Dave Chinner, Kees Cook, Mickaël Salaün,
Ronnie Sahlberg, Hyunchul Lee, linux-cifs, linux-kernel, llvm
2023-06-16 23:42 GMT+09:00, Arnd Bergmann <arnd@arndb.de>:
> On Fri, Jun 16, 2023, at 16:40, Namjae Jeon wrote:
>> 2023-06-16 18:07 GMT+09:00, Arnd Bergmann <arnd@kernel.org>:
>>> From: Arnd Bergmann <arnd@arndb.de>
>>>
>>> clang warns about a possible field overflow in a memcpy:
>>>
>>> In file included from fs/smb/server/smb_common.c:7:
>>> include/linux/fortify-string.h:583:4: error: call to
>>> '__write_overflow_field' declared with 'warning' attribute: detected
>>> write
>>> beyond size of field (1st parameter); maybe use struct_group()?
>>> [-Werror,-Wattribute-warning]
>>> __write_overflow_field(p_size_field, size);
>>>
>>> It appears to interpret the "&out[baselen + 4]" as referring to a single
>>> byte of the character array, while the equivalen "out + baselen + 4" is
>>> seen as an offset into the array.
>>>
>>> I don't see that kind of warning elsewhere, so just go with the simple
>>> rework.
>>>
>>> Fixes: e2f34481b24db ("cifsd: add server-side procedures for SMB3")
>>> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>>> ---
>>> fs/smb/server/smb_common.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/fs/smb/server/smb_common.c b/fs/smb/server/smb_common.c
>>> index a7e81067bc991..e3273fa640b07 100644
>>> --- a/fs/smb/server/smb_common.c
>>> +++ b/fs/smb/server/smb_common.c
>>> @@ -536,7 +536,7 @@ int ksmbd_extract_shortname(struct ksmbd_conn *conn,
>>> const char *longname,
>>> out[baselen + 3] = PERIOD;
>>>
>>> if (dot_present)
>>> - memcpy(&out[baselen + 4], extension, 4);
>>> + memcpy(out + baselen + 4, extension, 1);
>> Is there any reason to change copy bytes from 4 bytes to 1 byte?
>>
>
> No, that was an accident, this patch is wrong.
>
> I have to revisit this one and check if my change actually still works
> after I change it back to the correct length.
Okay:)
Thanks for your check!
>
> Arnd
>
^ permalink raw reply [flat|nested] 4+ messages in thread
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2023-06-16 9:07 [PATCH] smb: avoid field overflow warning Arnd Bergmann
2023-06-16 14:40 ` Namjae Jeon
2023-06-16 14:42 ` Arnd Bergmann
2023-06-16 14:49 ` Namjae Jeon
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