1. Patchew
  2. linux
  3. [RFC PATCH v5 0/7] mseal system mappings
  4. View patch

[RFC PATCH v5 2/7] selftests: x86: test_mremap_vdso: skip if vdso is msealed

jeffxu@chromium.org posted 7 patches 10 months, 1 week ago
There is a newer version of this series
[RFC PATCH v5 2/7] selftests: x86: test_mremap_vdso: skip if vdso is msealed
Posted by jeffxu@chromium.org 10 months, 1 week ago 
From: Jeff Xu <jeffxu@chromium.org>

Add code to detect if the vdso is memory sealed, skip the test
if it is.

Signed-off-by: Jeff Xu <jeffxu@chromium.org>
---
 .../testing/selftests/x86/test_mremap_vdso.c  | 38 +++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/tools/testing/selftests/x86/test_mremap_vdso.c b/tools/testing/selftests/x86/test_mremap_vdso.c
index d53959e03593..c68077c56b22 100644
--- a/tools/testing/selftests/x86/test_mremap_vdso.c
+++ b/tools/testing/selftests/x86/test_mremap_vdso.c
@@ -14,6 +14,7 @@
 #include <errno.h>
 #include <unistd.h>
 #include <string.h>
+#include <stdbool.h>
 
 #include <sys/mman.h>
 #include <sys/auxv.h>
@@ -55,13 +56,50 @@ static int try_to_remap(void *vdso_addr, unsigned long size)
 
 }
 
+#define VDSO_NAME "[vdso]"
+#define VMFLAGS "VmFlags:"
+#define MSEAL_FLAGS "sl"
+#define MAX_LINE_LEN 512
+
+bool vdso_sealed(FILE *maps)
+{
+	char line[MAX_LINE_LEN];
+	bool has_vdso = false;
+
+	while (fgets(line, sizeof(line), maps)) {
+		if (strstr(line, VDSO_NAME))
+			has_vdso = true;
+
+		if (has_vdso && !strncmp(line, VMFLAGS, strlen(VMFLAGS))) {
+			if (strstr(line, MSEAL_FLAGS))
+				return true;
+
+			return false;
+		}
+	}
+
+	return false;
+}
+
 int main(int argc, char **argv, char **envp)
 {
 	pid_t child;
+	FILE *maps;
 
 	ksft_print_header();
 	ksft_set_plan(1);
 
+	maps = fopen("/proc/self/smaps", "r");
+	if (!maps) {
+		ksft_test_result_skip("Could not open /proc/self/smaps\n");
+		return 0;
+	}
+
+	if (vdso_sealed(maps)) {
+		ksft_test_result_skip("vdso is sealed\n");
+		return 0;
+	}
+
 	child = fork();
 	if (child == -1)
 		ksft_exit_fail_msg("failed to fork (%d): %m\n", errno);
-- 
2.48.1.502.g6dc24dfdaf-goog
Re: [RFC PATCH v5 2/7] selftests: x86: test_mremap_vdso: skip if vdso is msealed
Posted by Thomas Weißschuh 10 months, 1 week ago 
On Wed, Feb 12, 2025 at 03:21:50AM +0000, jeffxu@chromium.org wrote:
> From: Jeff Xu <jeffxu@chromium.org>
> 
> Add code to detect if the vdso is memory sealed, skip the test
> if it is.
> 
> Signed-off-by: Jeff Xu <jeffxu@chromium.org>
> ---
>  .../testing/selftests/x86/test_mremap_vdso.c  | 38 +++++++++++++++++++
>  1 file changed, 38 insertions(+)
> 
> diff --git a/tools/testing/selftests/x86/test_mremap_vdso.c b/tools/testing/selftests/x86/test_mremap_vdso.c
> index d53959e03593..c68077c56b22 100644
> --- a/tools/testing/selftests/x86/test_mremap_vdso.c
> +++ b/tools/testing/selftests/x86/test_mremap_vdso.c
> @@ -14,6 +14,7 @@
>  #include <errno.h>
>  #include <unistd.h>
>  #include <string.h>
> +#include <stdbool.h>
>  
>  #include <sys/mman.h>
>  #include <sys/auxv.h>
> @@ -55,13 +56,50 @@ static int try_to_remap(void *vdso_addr, unsigned long size)
>  
>  }
>  
> +#define VDSO_NAME "[vdso]"
> +#define VMFLAGS "VmFlags:"
> +#define MSEAL_FLAGS "sl"
> +#define MAX_LINE_LEN 512
> +
> +bool vdso_sealed(FILE *maps)
> +{
> +	char line[MAX_LINE_LEN];
> +	bool has_vdso = false;
> +
> +	while (fgets(line, sizeof(line), maps)) {
> +		if (strstr(line, VDSO_NAME))
> +			has_vdso = true;
> +
> +		if (has_vdso && !strncmp(line, VMFLAGS, strlen(VMFLAGS))) {
> +			if (strstr(line, MSEAL_FLAGS))
> +				return true;
> +
> +			return false;

This only tests that any mapping after the vdso is sealed.
There is a real parser for /proc/self/smaps in
tools/testing/selftests/mm/vm_util.[ch], see check_vmflag_io().

> +		}
> +	}
> +
> +	return false;
> +}

<snip>
Re: [RFC PATCH v5 2/7] selftests: x86: test_mremap_vdso: skip if vdso is msealed
Posted by Jeff Xu 10 months, 1 week ago 
On Wed, Feb 12, 2025 at 5:04 AM Thomas Weißschuh
<thomas.weissschuh@linutronix.de> wrote:
>
> On Wed, Feb 12, 2025 at 03:21:50AM +0000, jeffxu@chromium.org wrote:
> > From: Jeff Xu <jeffxu@chromium.org>
> >
> > Add code to detect if the vdso is memory sealed, skip the test
> > if it is.
> >
> > Signed-off-by: Jeff Xu <jeffxu@chromium.org>
> > ---
> >  .../testing/selftests/x86/test_mremap_vdso.c  | 38 +++++++++++++++++++
> >  1 file changed, 38 insertions(+)
> >
> > diff --git a/tools/testing/selftests/x86/test_mremap_vdso.c b/tools/testing/selftests/x86/test_mremap_vdso.c
> > index d53959e03593..c68077c56b22 100644
> > --- a/tools/testing/selftests/x86/test_mremap_vdso.c
> > +++ b/tools/testing/selftests/x86/test_mremap_vdso.c
> > @@ -14,6 +14,7 @@
> >  #include <errno.h>
> >  #include <unistd.h>
> >  #include <string.h>
> > +#include <stdbool.h>
> >
> >  #include <sys/mman.h>
> >  #include <sys/auxv.h>
> > @@ -55,13 +56,50 @@ static int try_to_remap(void *vdso_addr, unsigned long size)
> >
> >  }
> >
> > +#define VDSO_NAME "[vdso]"
> > +#define VMFLAGS "VmFlags:"
> > +#define MSEAL_FLAGS "sl"
> > +#define MAX_LINE_LEN 512
> > +
> > +bool vdso_sealed(FILE *maps)
> > +{
> > +     char line[MAX_LINE_LEN];
> > +     bool has_vdso = false;
> > +
> > +     while (fgets(line, sizeof(line), maps)) {
> > +             if (strstr(line, VDSO_NAME))
> > +                     has_vdso = true;
> > +
> > +             if (has_vdso && !strncmp(line, VMFLAGS, strlen(VMFLAGS))) {
> > +                     if (strstr(line, MSEAL_FLAGS))
> > +                             return true;
> > +
> > +                     return false;
>
> This only tests that any mapping after the vdso is sealed.

The code above begins by searching for the "[vdso]" string, then looks
for the first line that starts with "VmFlags:", and looks for the "sl"
substring within that line. We're assuming the format of smaps won't
change from release to release.

> There is a real parser for /proc/self/smaps in
> tools/testing/selftests/mm/vm_util.[ch], see check_vmflag_io().
>
This test is in selftest/x86, which makes it hard to include the
vm_util from selftest/mm, if that's what you're asking.

If you are asking reusing the code logic from vm_util, the
check_vmflag_io() calls __get_smap_entry(addr, "VmFlags:", ...), which
begins by searching for address, then looks for the first line that
started with "VmFlags:", then check for the "io" within that line.
This is the same logic as my code, if I read the code correctly.

Thanks
-Jeff



> > +             }
> > +     }
> > +
> > +     return false;
> > +}
>
> <snip>
Re: [RFC PATCH v5 2/7] selftests: x86: test_mremap_vdso: skip if vdso is msealed
Posted by Kees Cook 10 months, 1 week ago 

On February 13, 2025 6:14:00 AM PST, Jeff Xu <jeffxu@chromium.org> wrote:
>On Wed, Feb 12, 2025 at 5:04 AM Thomas Weißschuh
><thomas.weissschuh@linutronix.de> wrote:
>>
>> On Wed, Feb 12, 2025 at 03:21:50AM +0000, jeffxu@chromium.org wrote:
>> > From: Jeff Xu <jeffxu@chromium.org>
>> >
>> > Add code to detect if the vdso is memory sealed, skip the test
>> > if it is.
>> >
>> > Signed-off-by: Jeff Xu <jeffxu@chromium.org>
>> > ---
>> >  .../testing/selftests/x86/test_mremap_vdso.c  | 38 +++++++++++++++++++
>> >  1 file changed, 38 insertions(+)
>> >
>> > diff --git a/tools/testing/selftests/x86/test_mremap_vdso.c b/tools/testing/selftests/x86/test_mremap_vdso.c
>> > index d53959e03593..c68077c56b22 100644
>> > --- a/tools/testing/selftests/x86/test_mremap_vdso.c
>> > +++ b/tools/testing/selftests/x86/test_mremap_vdso.c
>> > @@ -14,6 +14,7 @@
>> >  #include <errno.h>
>> >  #include <unistd.h>
>> >  #include <string.h>
>> > +#include <stdbool.h>
>> >
>> >  #include <sys/mman.h>
>> >  #include <sys/auxv.h>
>> > @@ -55,13 +56,50 @@ static int try_to_remap(void *vdso_addr, unsigned long size)
>> >
>> >  }
>> >
>> > +#define VDSO_NAME "[vdso]"
>> > +#define VMFLAGS "VmFlags:"
>> > +#define MSEAL_FLAGS "sl"
>> > +#define MAX_LINE_LEN 512
>> > +
>> > +bool vdso_sealed(FILE *maps)
>> > +{
>> > +     char line[MAX_LINE_LEN];
>> > +     bool has_vdso = false;
>> > +
>> > +     while (fgets(line, sizeof(line), maps)) {
>> > +             if (strstr(line, VDSO_NAME))
>> > +                     has_vdso = true;
>> > +
>> > +             if (has_vdso && !strncmp(line, VMFLAGS, strlen(VMFLAGS))) {
>> > +                     if (strstr(line, MSEAL_FLAGS))
>> > +                             return true;
>> > +
>> > +                     return false;
>>
>> This only tests that any mapping after the vdso is sealed.
>
>The code above begins by searching for the "[vdso]" string, then looks
>for the first line that starts with "VmFlags:", and looks for the "sl"
>substring within that line. We're assuming the format of smaps won't
>change from release to release.

Oh, I missed this in my reviews: nothing _resets_ has_vdso to false, so if any other mapping follows vdso that happens to be sealed, this will return true...

>
>> There is a real parser for /proc/self/smaps in
>> tools/testing/selftests/mm/vm_util.[ch], see check_vmflag_io().
>>
>This test is in selftest/x86, which makes it hard to include the
>vm_util from selftest/mm, if that's what you're asking.

Hm, we have done these kinds of inter-tests dependencies before. (E.g. seccomp includes stuff from the clone tests.) I think it should be possible if it can just be a header include. Linking across tests would be more frustrating.

-Kees

-- 
Kees Cook
Re: [RFC PATCH v5 2/7] selftests: x86: test_mremap_vdso: skip if vdso is msealed
Posted by Jeff Xu 10 months, 1 week ago 
On Thu, Feb 13, 2025 at 11:28 AM Kees Cook <kees@kernel.org> wrote:
>
>
>
> On February 13, 2025 6:14:00 AM PST, Jeff Xu <jeffxu@chromium.org> wrote:
> >On Wed, Feb 12, 2025 at 5:04 AM Thomas Weißschuh
> ><thomas.weissschuh@linutronix.de> wrote:
> >>
> >> On Wed, Feb 12, 2025 at 03:21:50AM +0000, jeffxu@chromium.org wrote:
> >> > From: Jeff Xu <jeffxu@chromium.org>
> >> >
> >> > Add code to detect if the vdso is memory sealed, skip the test
> >> > if it is.
> >> >
> >> > Signed-off-by: Jeff Xu <jeffxu@chromium.org>
> >> > ---
> >> >  .../testing/selftests/x86/test_mremap_vdso.c  | 38 +++++++++++++++++++
> >> >  1 file changed, 38 insertions(+)
> >> >
> >> > diff --git a/tools/testing/selftests/x86/test_mremap_vdso.c b/tools/testing/selftests/x86/test_mremap_vdso.c
> >> > index d53959e03593..c68077c56b22 100644
> >> > --- a/tools/testing/selftests/x86/test_mremap_vdso.c
> >> > +++ b/tools/testing/selftests/x86/test_mremap_vdso.c
> >> > @@ -14,6 +14,7 @@
> >> >  #include <errno.h>
> >> >  #include <unistd.h>
> >> >  #include <string.h>
> >> > +#include <stdbool.h>
> >> >
> >> >  #include <sys/mman.h>
> >> >  #include <sys/auxv.h>
> >> > @@ -55,13 +56,50 @@ static int try_to_remap(void *vdso_addr, unsigned long size)
> >> >
> >> >  }
> >> >
> >> > +#define VDSO_NAME "[vdso]"
> >> > +#define VMFLAGS "VmFlags:"
> >> > +#define MSEAL_FLAGS "sl"
> >> > +#define MAX_LINE_LEN 512
> >> > +
> >> > +bool vdso_sealed(FILE *maps)
> >> > +{
> >> > +     char line[MAX_LINE_LEN];
> >> > +     bool has_vdso = false;
> >> > +
> >> > +     while (fgets(line, sizeof(line), maps)) {
> >> > +             if (strstr(line, VDSO_NAME))
> >> > +                     has_vdso = true;
> >> > +
> >> > +             if (has_vdso && !strncmp(line, VMFLAGS, strlen(VMFLAGS))) {
> >> > +                     if (strstr(line, MSEAL_FLAGS))
> >> > +                             return true;
> >> > +
> >> > +                     return false;
> >>
> >> This only tests that any mapping after the vdso is sealed.
> >
> >The code above begins by searching for the "[vdso]" string, then looks
> >for the first line that starts with "VmFlags:", and looks for the "sl"
> >substring within that line. We're assuming the format of smaps won't
> >change from release to release.
>
> Oh, I missed this in my reviews: nothing _resets_ has_vdso to false, so if any other mapping follows vdso that happens to be sealed, this will return true...
>
It won't return the next mapping's sealing flag.
After finding the "[vdso]", if the next line that contains VMFLAGS
doesn't have the "sl" flag, the function returns false immediately.

> >
> >> There is a real parser for /proc/self/smaps in
> >> tools/testing/selftests/mm/vm_util.[ch], see check_vmflag_io().
> >>
> >This test is in selftest/x86, which makes it hard to include the
> >vm_util from selftest/mm, if that's what you're asking.
>
> Hm, we have done these kinds of inter-tests dependencies before. (E.g. seccomp includes stuff from the clone tests.) I think it should be possible if it can just be a header include. Linking across tests would be more frustrating.
>
I can switch to vm_util, I will need to add a new parsing function in
vm_util, the existing __get_smap_entry() only searches for vm's
starting address, not name.

Thanks
-Jeff


> -Kees

>
> --
> Kees Cook
Re: [RFC PATCH v5 2/7] selftests: x86: test_mremap_vdso: skip if vdso is msealed
Posted by Kees Cook 10 months, 1 week ago 

On February 13, 2025 2:20:01 PM PST, Jeff Xu <jeffxu@chromium.org> wrote:
>On Thu, Feb 13, 2025 at 11:28 AM Kees Cook <kees@kernel.org> wrote:
>>
>>
>>
>> On February 13, 2025 6:14:00 AM PST, Jeff Xu <jeffxu@chromium.org> wrote:
>> >On Wed, Feb 12, 2025 at 5:04 AM Thomas Weißschuh
>> ><thomas.weissschuh@linutronix.de> wrote:
>> >>
>> >> On Wed, Feb 12, 2025 at 03:21:50AM +0000, jeffxu@chromium.org wrote:
>> >> > From: Jeff Xu <jeffxu@chromium.org>
>> >> >
>> >> > Add code to detect if the vdso is memory sealed, skip the test
>> >> > if it is.
>> >> >
>> >> > Signed-off-by: Jeff Xu <jeffxu@chromium.org>
>> >> > ---
>> >> >  .../testing/selftests/x86/test_mremap_vdso.c  | 38 +++++++++++++++++++
>> >> >  1 file changed, 38 insertions(+)
>> >> >
>> >> > diff --git a/tools/testing/selftests/x86/test_mremap_vdso.c b/tools/testing/selftests/x86/test_mremap_vdso.c
>> >> > index d53959e03593..c68077c56b22 100644
>> >> > --- a/tools/testing/selftests/x86/test_mremap_vdso.c
>> >> > +++ b/tools/testing/selftests/x86/test_mremap_vdso.c
>> >> > @@ -14,6 +14,7 @@
>> >> >  #include <errno.h>
>> >> >  #include <unistd.h>
>> >> >  #include <string.h>
>> >> > +#include <stdbool.h>
>> >> >
>> >> >  #include <sys/mman.h>
>> >> >  #include <sys/auxv.h>
>> >> > @@ -55,13 +56,50 @@ static int try_to_remap(void *vdso_addr, unsigned long size)
>> >> >
>> >> >  }
>> >> >
>> >> > +#define VDSO_NAME "[vdso]"
>> >> > +#define VMFLAGS "VmFlags:"
>> >> > +#define MSEAL_FLAGS "sl"
>> >> > +#define MAX_LINE_LEN 512
>> >> > +
>> >> > +bool vdso_sealed(FILE *maps)
>> >> > +{
>> >> > +     char line[MAX_LINE_LEN];
>> >> > +     bool has_vdso = false;
>> >> > +
>> >> > +     while (fgets(line, sizeof(line), maps)) {
>> >> > +             if (strstr(line, VDSO_NAME))
>> >> > +                     has_vdso = true;
>> >> > +
>> >> > +             if (has_vdso && !strncmp(line, VMFLAGS, strlen(VMFLAGS))) {
>> >> > +                     if (strstr(line, MSEAL_FLAGS))
>> >> > +                             return true;
>> >> > +
>> >> > +                     return false;
>> >>
>> >> This only tests that any mapping after the vdso is sealed.
>> >
>> >The code above begins by searching for the "[vdso]" string, then looks
>> >for the first line that starts with "VmFlags:", and looks for the "sl"
>> >substring within that line. We're assuming the format of smaps won't
>> >change from release to release.
>>
>> Oh, I missed this in my reviews: nothing _resets_ has_vdso to false, so if any other mapping follows vdso that happens to be sealed, this will return true...
>>
>It won't return the next mapping's sealing flag.
>After finding the "[vdso]", if the next line that contains VMFLAGS
>doesn't have the "sl" flag, the function returns false immediately.

Oh! Agh, yes. You are right, this is all fine.

>I can switch to vm_util, I will need to add a new parsing function in
>vm_util, the existing __get_smap_entry() only searches for vm's
>starting address, not name.

Unless someone feels strongly about this, my instinct is to avoid the higher complexity of a cross-test thing.

-Kees


-- 
Kees Cook
Re: [RFC PATCH v5 2/7] selftests: x86: test_mremap_vdso: skip if vdso is msealed
Posted by Jeff Xu 10 months ago 
On Thu, Feb 13, 2025 at 6:52 PM Kees Cook <kees@kernel.org> wrote:
>
>
>
> On February 13, 2025 2:20:01 PM PST, Jeff Xu <jeffxu@chromium.org> wrote:
> >On Thu, Feb 13, 2025 at 11:28 AM Kees Cook <kees@kernel.org> wrote:
> >>
> >>
> >>
> >> On February 13, 2025 6:14:00 AM PST, Jeff Xu <jeffxu@chromium.org> wrote:
> >> >On Wed, Feb 12, 2025 at 5:04 AM Thomas Weißschuh
> >> ><thomas.weissschuh@linutronix.de> wrote:
> >> >>
> >> >> On Wed, Feb 12, 2025 at 03:21:50AM +0000, jeffxu@chromium.org wrote:
> >> >> > From: Jeff Xu <jeffxu@chromium.org>
> >> >> >
> >> >> > Add code to detect if the vdso is memory sealed, skip the test
> >> >> > if it is.
> >> >> >
> >> >> > Signed-off-by: Jeff Xu <jeffxu@chromium.org>
> >> >> > ---
> >> >> >  .../testing/selftests/x86/test_mremap_vdso.c  | 38 +++++++++++++++++++
> >> >> >  1 file changed, 38 insertions(+)
> >> >> >
> >> >> > diff --git a/tools/testing/selftests/x86/test_mremap_vdso.c b/tools/testing/selftests/x86/test_mremap_vdso.c
> >> >> > index d53959e03593..c68077c56b22 100644
> >> >> > --- a/tools/testing/selftests/x86/test_mremap_vdso.c
> >> >> > +++ b/tools/testing/selftests/x86/test_mremap_vdso.c
> >> >> > @@ -14,6 +14,7 @@
> >> >> >  #include <errno.h>
> >> >> >  #include <unistd.h>
> >> >> >  #include <string.h>
> >> >> > +#include <stdbool.h>
> >> >> >
> >> >> >  #include <sys/mman.h>
> >> >> >  #include <sys/auxv.h>
> >> >> > @@ -55,13 +56,50 @@ static int try_to_remap(void *vdso_addr, unsigned long size)
> >> >> >
> >> >> >  }
> >> >> >
> >> >> > +#define VDSO_NAME "[vdso]"
> >> >> > +#define VMFLAGS "VmFlags:"
> >> >> > +#define MSEAL_FLAGS "sl"
> >> >> > +#define MAX_LINE_LEN 512
> >> >> > +
> >> >> > +bool vdso_sealed(FILE *maps)
> >> >> > +{
> >> >> > +     char line[MAX_LINE_LEN];
> >> >> > +     bool has_vdso = false;
> >> >> > +
> >> >> > +     while (fgets(line, sizeof(line), maps)) {
> >> >> > +             if (strstr(line, VDSO_NAME))
> >> >> > +                     has_vdso = true;
> >> >> > +
> >> >> > +             if (has_vdso && !strncmp(line, VMFLAGS, strlen(VMFLAGS))) {
> >> >> > +                     if (strstr(line, MSEAL_FLAGS))
> >> >> > +                             return true;
> >> >> > +
> >> >> > +                     return false;
> >> >>
> >> >> This only tests that any mapping after the vdso is sealed.
> >> >
> >> >The code above begins by searching for the "[vdso]" string, then looks
> >> >for the first line that starts with "VmFlags:", and looks for the "sl"
> >> >substring within that line. We're assuming the format of smaps won't
> >> >change from release to release.
> >>
> >> Oh, I missed this in my reviews: nothing _resets_ has_vdso to false, so if any other mapping follows vdso that happens to be sealed, this will return true...
> >>
> >It won't return the next mapping's sealing flag.
> >After finding the "[vdso]", if the next line that contains VMFLAGS
> >doesn't have the "sl" flag, the function returns false immediately.
>
> Oh! Agh, yes. You are right, this is all fine.
>
> >I can switch to vm_util, I will need to add a new parsing function in
> >vm_util, the existing __get_smap_entry() only searches for vm's
> >starting address, not name.
>
> Unless someone feels strongly about this, my instinct is to avoid the higher complexity of a cross-test thing.
>
OK. I will keep the existing test.

If we decide to use vm_util, it would be best to refactor it
separately later on. The existing vm_util can't be used as is for my
needs, so some refactoring would be necessary.


Thanks
-Jeff

> -Kees
>
>
> --
> Kees Cook

Patchew 2.1-devel-b67e4c2

© 2016 - 2025 Red Hat, Inc.