On Tue, Feb 25, 2025 at 02:37:46PM -0800, Jeff Xu wrote:
> On Mon, Feb 24, 2025 at 10:15 PM Lorenzo Stoakes
> <lorenzo.stoakes@xxxxxxxxxx> wrote:
> >
> > On Mon, Feb 24, 2025 at 10:52:41PM +0000, jeffxu@xxxxxxxxxxxx wrote:
> > > From: Jeff Xu <jeffxu@xxxxxxxxxxxx>
> > >
> > > Add code to detect if the vdso is memory sealed, skip the test
> > > if it is.
> >
> > I feel this is a little succinct of a commit message, but I guess it gets to the
> > heart of what you're doing here.
> >
> > Fundamentally I mean it makes sense, but I'm concerned that x86 has a test
> > -expliictly checking- whether mremap() of VDSO is possible - are there cases
> > where x86 might want to do this internal to the kernel?
> >
> > I guess not since this is essentially a userland self test and probably
> > asserting you can do this in the way rr, etc. do.
> >
> > >
> > > Signed-off-by: Jeff Xu <jeffxu@xxxxxxxxxxxx>
> > > Reviewed-by: Kees Cook <kees@xxxxxxxxxx>
> >
> > Anyway, this aside, this looks fine, aside from nit below, so:
> >
> > Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
> >
> > > ---
> > > .../testing/selftests/x86/test_mremap_vdso.c | 43 +++++++++++++++++++
> > > 1 file changed, 43 insertions(+)
> > >
> > > diff --git a/tools/testing/selftests/x86/test_mremap_vdso.c b/tools/testing/selftests/x86/test_mremap_vdso.c
> > > index d53959e03593..94bee6e0c813 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 +56,55 @@ 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)
> >
> > Should be static?
> >
> sure.
Thanks! :)
>
> > > +{
> > > + 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, errno=%d\n",
> > > + errno);
> > > +
> > > + return 0;
> > > + }
> > > +
> > > + if (vdso_sealed(maps)) {
> > > + ksft_test_result_skip("vdso is sealed\n");
> > > + return 0;
> > > + }
> > > +
> > > + fclose(maps);
> > > +
> > > child = fork();
> > > if (child == -1)
> > > ksft_exit_fail_msg("failed to fork (%d): %m\n", errno);
> > > --
> > > 2.48.1.658.g4767266eb4-goog
> > >
