linux ttyname{_r}: Make tty checks consistent

In the ttyname and ttyname_r routines on Linux, at several points it needs to
check if a given TTY is the TTY we are looking for. It used to be that this
check was (to see if `maybe` is `mytty`):

       __xstat64(_STAT_VER, maybe_filename, &maybe) == 0
    #ifdef _STATBUF_ST_RDEV
       && S_ISCHR(maybe.st_mode) && maybe.st_rdev == mytty.st_rdev
    #else
       && maybe.st_ino == mytty.st_ino && maybe.st_dev == mytty.st_dev
    #endif

This check appears in several places.

Then, one of the changes made in commit 15e9a4f378c8607c2ae1aa465436af4321db0e23
was to change that check to:

       __xstat64(_STAT_VER, maybe_filename, &maybe) == 0
    #ifdef _STATBUF_ST_RDEV
       && S_ISCHR(maybe.st_mode) && maybe.st_rdev == mytty.st_rdev
    #endif
       && maybe.st_ino == mytty.st_ino && maybe.st_dev == mytty.st_dev

That is, it made the st_ino and st_dev parts of the check happen even if we have
the st_rdev member. This is an important change, because the kernel allows
multiple devpts filesystem instances to be created; a device file in one devpts
instance may share the same st_rdev with a file in another devpts instance, but
they aren't the same file.

This check appears twice in each file (ttyname.c and ttyname_r.c), once (in
ttyname and __ttyname_r) to check if a candidate file found by inspecting /proc
is the desired TTY, and once (in getttyname and getttyname_r) to check if a
candidate file found by searching /dev is the desired TTY. However, 15e9a4f
only updated the checks for files found via /proc; but the concern about
collisions between devpts instances is just as valid for files found via /dev.

So, update all 4 occurrences the check to be consistent with the version of the
check introduced in 15e9a4f. Make it easy to keep all 4 occurrences of the
check consistent by pulling it in to a static inline function, is_mytty.

Reviewed-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/ChangeLog b/ChangeLog
index bb960c04bdda7754ffd94077d502c550be30e7c9..00f388369f70cd9a69a515bfa32811c7c6beb358 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,12 @@
 2017-11-15  Luke Shumaker  <lukeshu@parabola.nu>
 
+       [BZ #22145]
+       * sysdeps/unix/sysv/linux/ttyname.h (is_mytty): New function.
+       * sysdeps/unix/sysv/linux/ttyname.c (getttyname): Call is_mytty.
+       (ttyname): Likewise.
+       * sysdeps/unix/sysv/linux/ttyname_r.c (getttyname_r): Likewise.
+       (__ttyname_r): Likewise.
+
        * sysdeps/unix/sysv/linux/ttyname.h (is_pty): Change return type from
        int to bool.
 

diff --git a/sysdeps/unix/sysv/linux/ttyname.c b/sysdeps/unix/sysv/linux/ttyname.c
index 116cf350e562fa0b6f9d1255d542dafbea4292ac..6e97d2d4554cc87d5b714003db3651393149d153 100644 (file)
--- a/sysdeps/unix/sysv/linux/ttyname.c
+++ b/sysdeps/unix/sysv/linux/ttyname.c
@@ -35,14 +35,14 @@
 char *__ttyname;
 #endif
 
-static char *getttyname (const char *dev, dev_t mydev,
-                        ino64_t myino, int save, int *dostat);
+static char *getttyname (const char *dev, const struct stat64 *mytty,
+                        int save, int *dostat);
 
 libc_freeres_ptr (static char *getttyname_name);
 
 static char *
 attribute_compat_text_section
-getttyname (const char *dev, dev_t mydev, ino64_t myino, int save, int *dostat)
+getttyname (const char *dev, const struct stat64 *mytty, int save, int *dostat)
 {
   static size_t namelen;
   struct stat64 st;
@@ -63,7 +63,7 @@ getttyname (const char *dev, dev_t mydev, ino64_t myino, int save, int *dostat)
     *((char *) __mempcpy (getttyname_name, dev, devlen - 1)) = '/';
 
   while ((d = __readdir64 (dirstream)) != NULL)
-    if ((d->d_fileno == myino || *dostat)
+    if ((d->d_fileno == mytty->st_ino || *dostat)
        && strcmp (d->d_name, "stdin")
        && strcmp (d->d_name, "stdout")
        && strcmp (d->d_name, "stderr"))
@@ -85,12 +85,7 @@ getttyname (const char *dev, dev_t mydev, ino64_t myino, int save, int *dostat)
          }
        memcpy (&getttyname_name[devlen], d->d_name, dlen);
        if (__xstat64 (_STAT_VER, getttyname_name, &st) == 0
-#ifdef _STATBUF_ST_RDEV
-           && S_ISCHR (st.st_mode) && st.st_rdev == mydev
-#else
-           && d->d_fileno == myino && st.st_dev == mydev
-#endif
-          )
+           && is_mytty (mytty, &st))
          {
            (void) __closedir (dirstream);
 #if 0
@@ -167,12 +162,7 @@ ttyname (int fd)
       /* Verify readlink result, fall back on iterating through devices.  */
       if (ttyname_buf[0] == '/'
          && __xstat64 (_STAT_VER, ttyname_buf, &st1) == 0
-#ifdef _STATBUF_ST_RDEV
-         && S_ISCHR (st1.st_mode)
-         && st1.st_rdev == st.st_rdev
-#endif
-         && st1.st_ino == st.st_ino
-         && st1.st_dev == st.st_dev)
+         && is_mytty (&st, &st1))
        return ttyname_buf;
 
       /* If the link doesn't exist, then it points to a device in another
@@ -186,11 +176,7 @@ ttyname (int fd)
 
   if (__xstat64 (_STAT_VER, "/dev/pts", &st1) == 0 && S_ISDIR (st1.st_mode))
     {
-#ifdef _STATBUF_ST_RDEV
-      name = getttyname ("/dev/pts", st.st_rdev, st.st_ino, save, &dostat);
-#else
-      name = getttyname ("/dev/pts", st.st_dev, st.st_ino, save, &dostat);
-#endif
+      name = getttyname ("/dev/pts", &st, save, &dostat);
     }
   else
     {
@@ -200,21 +186,13 @@ ttyname (int fd)
 
   if (!name && dostat != -1)
     {
-#ifdef _STATBUF_ST_RDEV
-      name = getttyname ("/dev", st.st_rdev, st.st_ino, save, &dostat);
-#else
-      name = getttyname ("/dev", st.st_dev, st.st_ino, save, &dostat);
-#endif
+      name = getttyname ("/dev", &st, save, &dostat);
     }
 
   if (!name && dostat != -1)
     {
       dostat = 1;
-#ifdef _STATBUF_ST_RDEV
-      name = getttyname ("/dev", st.st_rdev, st.st_ino, save, &dostat);
-#else
-      name = getttyname ("/dev", st.st_dev, st.st_ino, save, &dostat);
-#endif
+      name = getttyname ("/dev", &st, save, &dostat);
     }
 
   return name;

diff --git a/sysdeps/unix/sysv/linux/ttyname.h b/sysdeps/unix/sysv/linux/ttyname.h
index cdaf60fb871e2af0ce73dc76df5893ca0fbd93a6..48181330a9d055ca78f1cdbe25225b0462780a01 100644 (file)
--- a/sysdeps/unix/sysv/linux/ttyname.h
+++ b/sysdeps/unix/sysv/linux/ttyname.h
@@ -34,3 +34,15 @@ is_pty (struct stat64 *sb)
   return false;
 #endif
 }
+
+static inline bool
+is_mytty (const struct stat64 *mytty, const struct stat64 *maybe)
+{
+  return (maybe->st_ino == mytty->st_ino
+         && maybe->st_dev == mytty->st_dev
+#ifdef _STATBUF_ST_RDEV
+         && S_ISCHR (maybe->st_mode)
+         && maybe->st_rdev == mytty->st_rdev
+#endif
+         );
+}

diff --git a/sysdeps/unix/sysv/linux/ttyname_r.c b/sysdeps/unix/sysv/linux/ttyname_r.c
index 18f35ef2b73c92bff8eef545aa96979399763fd6..58eb919c3fe61ed8f8e9aff5d5564e6e1ae3841c 100644 (file)
--- a/sysdeps/unix/sysv/linux/ttyname_r.c
+++ b/sysdeps/unix/sysv/linux/ttyname_r.c
@@ -31,12 +31,12 @@
 #include "ttyname.h"
 
 static int getttyname_r (char *buf, size_t buflen,
-                        dev_t mydev, ino64_t myino, int save,
+                        const struct stat64 *mytty, int save,
                         int *dostat);
 
 static int
 attribute_compat_text_section
-getttyname_r (char *buf, size_t buflen, dev_t mydev, ino64_t myino,
+getttyname_r (char *buf, size_t buflen, const struct stat64 *mytty,
              int save, int *dostat)
 {
   struct stat64 st;
@@ -52,7 +52,7 @@ getttyname_r (char *buf, size_t buflen, dev_t mydev, ino64_t myino,
     }
 
   while ((d = __readdir64 (dirstream)) != NULL)
-    if ((d->d_fileno == myino || *dostat)
+    if ((d->d_fileno == mytty->st_ino || *dostat)
        && strcmp (d->d_name, "stdin")
        && strcmp (d->d_name, "stdout")
        && strcmp (d->d_name, "stderr"))
@@ -72,12 +72,7 @@ getttyname_r (char *buf, size_t buflen, dev_t mydev, ino64_t myino,
        cp[0] = '\0';
 
        if (__xstat64 (_STAT_VER, buf, &st) == 0
-#ifdef _STATBUF_ST_RDEV
-           && S_ISCHR (st.st_mode) && st.st_rdev == mydev
-#else
-           && d->d_fileno == myino && st.st_dev == mydev
-#endif
-          )
+           && is_mytty (mytty, &st))
          {
            (void) __closedir (dirstream);
            __set_errno (save);
@@ -151,12 +146,7 @@ __ttyname_r (int fd, char *buf, size_t buflen)
       /* Verify readlink result, fall back on iterating through devices.  */
       if (buf[0] == '/'
          && __xstat64 (_STAT_VER, buf, &st1) == 0
-#ifdef _STATBUF_ST_RDEV
-         && S_ISCHR (st1.st_mode)
-         && st1.st_rdev == st.st_rdev
-#endif
-         && st1.st_ino == st.st_ino
-         && st1.st_dev == st.st_dev)
+         && is_mytty (&st, &st1))
        return 0;
 
       /* If the link doesn't exist, then it points to a device in another
@@ -175,13 +165,8 @@ __ttyname_r (int fd, char *buf, size_t buflen)
 
   if (__xstat64 (_STAT_VER, buf, &st1) == 0 && S_ISDIR (st1.st_mode))
     {
-#ifdef _STATBUF_ST_RDEV
-      ret = getttyname_r (buf, buflen, st.st_rdev, st.st_ino, save,
+      ret = getttyname_r (buf, buflen, &st, save,
                          &dostat);
-#else
-      ret = getttyname_r (buf, buflen, st.st_dev, st.st_ino, save,
-                         &dostat);
-#endif
     }
   else
     {
@@ -193,26 +178,16 @@ __ttyname_r (int fd, char *buf, size_t buflen)
     {
       buf[sizeof ("/dev/") - 1] = '\0';
       buflen += sizeof ("pts/") - 1;
-#ifdef _STATBUF_ST_RDEV
-      ret = getttyname_r (buf, buflen, st.st_rdev, st.st_ino, save,
-                         &dostat);
-#else
-      ret = getttyname_r (buf, buflen, st.st_dev, st.st_ino, save,
+      ret = getttyname_r (buf, buflen, &st, save,
                          &dostat);
-#endif
     }
 
   if (ret && dostat != -1)
     {
       buf[sizeof ("/dev/") - 1] = '\0';
       dostat = 1;
-#ifdef _STATBUF_ST_RDEV
-      ret = getttyname_r (buf, buflen, st.st_rdev, st.st_ino,
-                         save, &dostat);
-#else
-      ret = getttyname_r (buf, buflen, st.st_dev, st.st_ino,
+      ret = getttyname_r (buf, buflen, &st,
                          save, &dostat);
-#endif
     }
 
   return ret;