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Date:   Tue, 10 Oct 2023 11:51:32 +0800
From:   Binbin Wu <binbin.wu@...ux.intel.com>
To:     kirill.shutemov@...ux.intel.com
Cc:     dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
        shuah@...nel.org, linux-kselftest@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, weihong.zhang@...el.com
Subject: Re: [PATCH] selftests/x86/lam: Zero out buffer for readlink()



On 9/27/2023 7:02 PM, kirill.shutemov@...ux.intel.com wrote:
> On Sun, Sep 24, 2023 at 07:33:46AM +0800, Binbin Wu wrote:
>> Zero out the buffer for readlink() since readlink() does not append a
>> terminating null byte to the buffer.
>>
>> Fixes: 833c12ce0f430 ("selftests/x86/lam: Add inherit test cases for linear-address masking")
>>
>> Signed-off-by: Binbin Wu <binbin.wu@...ux.intel.com>
>> ---
>>   tools/testing/selftests/x86/lam.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/tools/testing/selftests/x86/lam.c b/tools/testing/selftests/x86/lam.c
>> index eb0e46905bf9..9f06942a8e25 100644
>> --- a/tools/testing/selftests/x86/lam.c
>> +++ b/tools/testing/selftests/x86/lam.c
>> @@ -680,7 +680,7 @@ static int handle_execve(struct testcases *test)
>>   		perror("Fork failed.");
>>   		ret = 1;
>>   	} else if (pid == 0) {
>> -		char path[PATH_MAX];
>> +		char path[PATH_MAX] = {0};
> Shouldn't it be PATH_MAX+1 to handle the case when readlink(2) stores
> exactly PATH_MAX bytes into the buffer?
According to the definition of PATH_MAX in include/uapi/linux/limits.h
#define PATH_MAX        4096    /* # chars in a path name including nul */

IIUC, Linux limits the path length to 4095 and PATH_MAX includes the 
terminating nul.


>
>>   
>>   		/* Set LAM mode in parent process */
>>   		if (set_lam(lam) != 0)
>>
>> base-commit: ce9ecca0238b140b88f43859b211c9fdfd8e5b70
>> -- 
>> 2.25.1
>>

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