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 <[email protected]>
---
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};
/* Set LAM mode in parent process */
if (set_lam(lam) != 0)
base-commit: ce9ecca0238b140b88f43859b211c9fdfd8e5b70
--
2.25.1
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 <[email protected]>
> ---
> 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?
>
> /* Set LAM mode in parent process */
> if (set_lam(lam) != 0)
>
> base-commit: ce9ecca0238b140b88f43859b211c9fdfd8e5b70
> --
> 2.25.1
>
--
Kiryl Shutsemau / Kirill A. Shutemov
On 9/27/2023 7:02 PM, [email protected] 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 <[email protected]>
>> ---
>> 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
>>
On Tue, Oct 10, 2023 at 11:51:32AM +0800, Binbin Wu wrote:
>
>
> On 9/27/2023 7:02 PM, [email protected] 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 <[email protected]>
> > > ---
> > > 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.
Consider the case when kernel bump PATH_MAX to 8192. The binary that
compiled from lam.c against the older kernel headers will get compromised.
Increase the size of the buffer by one or pass PATH_MAX - 1 as buffer size
to readlink(2).
--
Kiryl Shutsemau / Kirill A. Shutemov
On 10/10/2023 1:46 PM, [email protected] wrote:
> On Tue, Oct 10, 2023 at 11:51:32AM +0800, Binbin Wu wrote:
>>
>> On 9/27/2023 7:02 PM, [email protected] 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 <[email protected]>
>>>> ---
>>>> 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.
> Consider the case when kernel bump PATH_MAX to 8192. The binary that
> compiled from lam.c against the older kernel headers will get compromised.
>
> Increase the size of the buffer by one or pass PATH_MAX - 1 as buffer size
> to readlink(2).
Make sense, thanks!
I will send a new version as following:
diff --git a/tools/testing/selftests/x86/lam.c
b/tools/testing/selftests/x86/lam.c
index eb0e46905bf9..8f9b06d9ce03 100644
--- a/tools/testing/selftests/x86/lam.c
+++ b/tools/testing/selftests/x86/lam.c
@@ -573,7 +573,7 @@ int do_uring(unsigned long lam)
char path[PATH_MAX] = {0};
/* get current process path */
- if (readlink("/proc/self/exe", path, PATH_MAX) <= 0)
+ if (readlink("/proc/self/exe", path, PATH_MAX - 1) <= 0)
return 1;
int file_fd = open(path, O_RDONLY);
@@ -680,14 +680,14 @@ 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};
/* Set LAM mode in parent process */
if (set_lam(lam) != 0)
return 1;
/* Get current binary's path and the binary was run by
execve */
- if (readlink("/proc/self/exe", path, PATH_MAX) <= 0)
+ if (readlink("/proc/self/exe", path, PATH_MAX - 1) <= 0)
exit(-1);
/* run binary to get LAM mode and return to parent
process */
>