4.15-stable review patch. If anyone has any objections, please let me know.

------------------

From: Dominik Brodowski linux@dominikbrodowski.net

commit d8e92de8ef952bed88c56c7a44c02d8dcae0984e upstream.

Replace a couple of magically connected buffer length literal constants with a common definition that makes their relationship obvious. Also document why our sscanf() usage is safe.

No intended functional changes.

Suggested-by: Ingo Molnar mingo@kernel.org Signed-off-by: Dominik Brodowski linux@dominikbrodowski.net Cc: Andrew Lutomirski luto@kernel.org Cc: Andy Lutomirski luto@kernel.org Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Cc: linux-kselftest@vger.kernel.org Cc: shuah@kernel.org Link: http://lkml.kernel.org/r/20180211205924.GA23210@light.dominikbrodowski.net Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- tools/testing/selftests/x86/test_vdso.c | 11 ++++++++--- tools/testing/selftests/x86/test_vsyscall.c | 11 ++++++++--- 2 files changed, 16 insertions(+), 6 deletions(-)

--- a/tools/testing/selftests/x86/test_vdso.c +++ b/tools/testing/selftests/x86/test_vdso.c @@ -26,6 +26,9 @@ # endif #endif

+/* max length of lines in /proc/self/maps - anything longer is skipped here */ +#define MAPS_LINE_LEN 128 + int nerrs = 0;

typedef long (*getcpu_t)(unsigned *, unsigned *, void *); @@ -37,17 +40,19 @@ static void *vsyscall_getcpu(void) { #ifdef __x86_64__ FILE *maps; - char line[128]; + char line[MAPS_LINE_LEN]; bool found = false;

maps = fopen("/proc/self/maps", "r"); if (!maps) /* might still be present, but ignore it here, as we test vDSO not vsyscall */ return NULL;

- while (fgets(line, sizeof(line), maps)) { + while (fgets(line, MAPS_LINE_LEN, maps)) { char r, x; void *start, *end; - char name[128]; + char name[MAPS_LINE_LEN]; + + /* sscanf() is safe here as strlen(name) >= strlen(line) */ if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s", &start, &end, &r, &x, name) != 5) continue; --- a/tools/testing/selftests/x86/test_vsyscall.c +++ b/tools/testing/selftests/x86/test_vsyscall.c @@ -33,6 +33,9 @@ # endif #endif

+/* max length of lines in /proc/self/maps - anything longer is skipped here */ +#define MAPS_LINE_LEN 128 + static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *), int flags) { @@ -98,7 +101,7 @@ static int init_vsys(void) #ifdef __x86_64__ int nerrs = 0; FILE *maps; - char line[128]; + char line[MAPS_LINE_LEN]; bool found = false;

maps = fopen("/proc/self/maps", "r"); @@ -108,10 +111,12 @@ static int init_vsys(void) return 0; }

- while (fgets(line, sizeof(line), maps)) { + while (fgets(line, MAPS_LINE_LEN, maps)) { char r, x; void *start, *end; - char name[128]; + char name[MAPS_LINE_LEN]; + + /* sscanf() is safe here as strlen(name) >= strlen(line) */ if (sscanf(line, "%p-%p %c-%cp %*x %*x:%*x %*u %s", &start, &end, &r, &x, name) != 5) continue;

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