Commit-ID:  d8e92de8ef952bed88c56c7a44c02d8dcae0984e
Gitweb:     https://git.kernel.org/tip/d8e92de8ef952bed88c56c7a44c02d8dcae0984e
Author:     Dominik Brodowski <li...@dominikbrodowski.net>
AuthorDate: Sun, 11 Feb 2018 21:59:24 +0100
Committer:  Ingo Molnar <mi...@kernel.org>
CommitDate: Tue, 13 Feb 2018 09:04:56 +0100

selftests/x86: Clean up and document sscanf() usage

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 <mi...@kernel.org>
Signed-off-by: Dominik Brodowski <li...@dominikbrodowski.net>
Cc: Andrew Lutomirski <l...@kernel.org>
Cc: Andy Lutomirski <l...@kernel.org>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: linux-kselft...@vger.kernel.org
Cc: sh...@kernel.org
Link: http://lkml.kernel.org/r/20180211205924.ga23...@light.dominikbrodowski.net
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---
 tools/testing/selftests/x86/test_vdso.c     | 11 ++++++++---
 tools/testing/selftests/x86/test_vsyscall.c | 11 ++++++++---
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/x86/test_vdso.c 
b/tools/testing/selftests/x86/test_vdso.c
index 558c820..2352590 100644
--- 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;
diff --git a/tools/testing/selftests/x86/test_vsyscall.c 
b/tools/testing/selftests/x86/test_vsyscall.c
index 7a744fa..be81621 100644
--- 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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