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SubjectRe: [PATCH v1] qnx4_match: do not over run the buffer
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> On Nov 21, 2020, at 4:40 PM, Anders Larsen <al@alarsen.net> wrote:
>
> On Friday, 2020-11-20 22:21 Tong Zhang wrote:
>> the di_fname may not terminated by '\0', use strnlen to prevent buffer
>> overrun
>>
>> ---
>> fs/qnx4/namei.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/fs/qnx4/namei.c b/fs/qnx4/namei.c
>> index 8d72221735d7..c0e79094f578 100644
>> --- a/fs/qnx4/namei.c
>> +++ b/fs/qnx4/namei.c
>> @@ -40,7 +40,7 @@ static int qnx4_match(int len, const char *name,
>> } else {
>> namelen = QNX4_SHORT_NAME_MAX;
>> }
>> - thislen = strlen( de->di_fname );
>> + thislen = strnlen( de->di_fname, QNX4_SHORT_NAME_MAX );
>
> that should be
> + thislen = strnlen( de->di_fname, namelen );
> otherwise the length of a filename would always be limited to QNX4_SHORT_NAME_MAX (16) characters.
>
Why should we put something bigger here if the size of qnx4_inode_entry->di_fname is QNX4_SHORT_NAME_MAX.
Won’t that be a problem?

>> if ( thislen > namelen )
>> thislen = namelen;
>
> These two lines can be dropped now, as the result of strnlen() cannot exceed namelen anyway.
>
> Cheers
> Anders
>
>

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