sysvipc: Fix IPC_INFO and SHM_INFO handling [BZ #26636]

Both commands are Linux extensions where the third argument is either
a 'struct shminfo' (IPC_INFO) or a 'struct shm_info' (SHM_INFO) instead
of 'struct shmid_ds'.  And their information does not contain any time
related fields, so there is no need to extra conversion for __IPC_TIME64.

The regression testcase checks for Linux specifix SysV ipc message
control extension.  For SHM_INFO it tries to match the values against the
tunable /proc values and for MSG_STAT/MSG_STAT_ANY it check if the create\
shared memory is within the global list returned by the kernel.

Checked on x86_64-linux-gnu and on i686-linux-gnu (Linux v5.4 and on
Linux v4.15).

3 files changed, 204 insertions, 7 deletions

diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index d760debf40..09604e128b 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -103,7 +103,7 @@ tests += tst-clone tst-clone2 tst-clone3 tst-fanotify tst-personality \
 	 tst-quota tst-sync_file_range tst-sysconf-iov_max tst-ttyname \
 	 test-errno-linux tst-memfd_create tst-mlock2 tst-pkey \
 	 tst-rlimit-infinity tst-ofdlocks tst-gettid tst-gettid-kill \
-	 tst-tgkill tst-sysvsem-linux tst-sysvmsg-linux
+	 tst-tgkill tst-sysvsem-linux tst-sysvmsg-linux tst-sysvshm-linux
 tests-internal += tst-ofdlocks-compat tst-sigcontext-get_pc
 
 CFLAGS-tst-sigcontext-get_pc.c = -fasynchronous-unwind-tables
diff --git a/sysdeps/unix/sysv/linux/shmctl.c b/sysdeps/unix/sysv/linux/shmctl.c
index 76d88441f1..1d19a798b1 100644
--- a/sysdeps/unix/sysv/linux/shmctl.c
+++ b/sysdeps/unix/sysv/linux/shmctl.c
@@ -90,8 +90,15 @@ __shmctl64 (int shmid, int cmd, struct __shmid64_ds *buf)
   struct kernel_shmid64_ds kshmid, *arg = NULL;
   if (buf != NULL)
     {
-      shmid64_to_kshmid64 (buf, &kshmid);
-      arg = &kshmid;
+      /* This is a Linux extension where kernel expects either a
+	 'struct shminfo' (IPC_INFO) or 'struct shm_info' (SHM_INFO).  */
+      if (cmd == IPC_INFO || cmd == SHM_INFO)
+	arg = (struct kernel_shmid64_ds *) buf;
+      else
+	{
+	  shmid64_to_kshmid64 (buf, &kshmid);
+	  arg = &kshmid;
+	}
     }
 # ifdef __ASSUME_SYSVIPC_BROKEN_MODE_T
   if (cmd == IPC_SET)
@@ -107,7 +114,6 @@ __shmctl64 (int shmid, int cmd, struct __shmid64_ds *buf)
 
   switch (cmd)
     {
-      case IPC_INFO:
       case IPC_STAT:
       case SHM_STAT:
       case SHM_STAT_ANY:
@@ -168,8 +174,15 @@ __shmctl (int shmid, int cmd, struct shmid_ds *buf)
   struct __shmid64_ds shmid64, *buf64 = NULL;
   if (buf != NULL)
     {
-      shmid_to_shmid64 (&shmid64, buf);
-      buf64 = &shmid64;
+      /* This is a Linux extension where kernel expects either a
+	 'struct shminfo' (IPC_INFO) or 'struct shm_info' (SHM_INFO).  */
+      if (cmd == IPC_INFO || cmd == SHM_INFO)
+	buf64 = (struct __shmid64_ds *) buf;
+      else
+	{
+	  shmid_to_shmid64 (&shmid64, buf);
+	  buf64 = &shmid64;
+	}
     }
 
   int ret = __shmctl64 (shmid, cmd, buf64);
@@ -178,7 +191,6 @@ __shmctl (int shmid, int cmd, struct shmid_ds *buf)
 
   switch (cmd)
     {
-      case IPC_INFO:
       case IPC_STAT:
       case SHM_STAT:
       case SHM_STAT_ANY:
diff --git a/sysdeps/unix/sysv/linux/tst-sysvshm-linux.c b/sysdeps/unix/sysv/linux/tst-sysvshm-linux.c
new file mode 100644
index 0000000000..7128ae2e14
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-sysvshm-linux.c
@@ -0,0 +1,185 @@
+/* Basic tests for Linux SYSV shared memory extensions.
+   Copyright (C) 2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <sys/ipc.h>
+#include <sys/shm.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <inttypes.h>
+#include <limits.h>
+
+#include <support/check.h>
+#include <support/temp_file.h>
+
+#define SHM_MODE 0644
+
+/* These are for the temporary file we generate.  */
+static char *name;
+static int shmid;
+static long int pgsz;
+
+static void
+remove_shm (void)
+{
+  /* Enforce message queue removal in case of early test failure.
+     Ignore error since the shm may already have being removed.  */
+  shmctl (shmid, IPC_RMID, NULL);
+}
+
+static void
+do_prepare (int argc, char *argv[])
+{
+  TEST_VERIFY_EXIT (create_temp_file ("tst-sysvshm.", &name) != -1);
+}
+
+#define PREPARE do_prepare
+
+struct test_shminfo
+{
+  unsigned long int shmall;
+  unsigned long int shmmax;
+  unsigned long int shmmni;
+};
+
+/* It tries to obtain some system-wide SysV shared memory information from
+   /proc to check against IPC_INFO/SHM_INFO.  The /proc only returns the
+   tunables value of SHMALL, SHMMAX, and SHMMNI.  */
+
+static uint64_t
+read_proc_file (const char *file)
+{
+  FILE *f = fopen (file, "r");
+  if (f == NULL)
+    FAIL_UNSUPPORTED ("/proc is not mounted or %s is not available", file);
+
+  /* Handle 32-bit binaries running on 64-bit kernels.  */
+  uint64_t v;
+  int r = fscanf (f, "%" SCNu64, &v);
+  TEST_VERIFY_EXIT (r == 1);
+
+  fclose (f);
+  return v;
+}
+
+
+/* Check if the message queue with IDX (index into the kernel's internal
+   array) matches the one with KEY.  The CMD is either SHM_STAT or
+   SHM_STAT_ANY.  */
+
+static bool
+check_shminfo (int idx, key_t key, int cmd)
+{
+  struct shmid_ds shminfo;
+  int sid = shmctl (idx, cmd, &shminfo);
+  /* Ignore unused array slot returned by the kernel or information from
+     unknown message queue.  */
+  if ((sid == -1 && errno == EINVAL) || sid != shmid)
+    return false;
+
+  if (sid == -1)
+    FAIL_EXIT1 ("shmctl with %s failed: %m",
+		cmd == SHM_STAT ? "SHM_STAT" : "SHM_STAT_ANY");
+
+  TEST_COMPARE (shminfo.shm_perm.__key, key);
+  TEST_COMPARE (shminfo.shm_perm.mode, SHM_MODE);
+  TEST_COMPARE (shminfo.shm_segsz, pgsz);
+
+  return true;
+}
+
+static int
+do_test (void)
+{
+  atexit (remove_shm);
+
+  pgsz = sysconf (_SC_PAGESIZE);
+  if (pgsz == -1)
+    FAIL_EXIT1 ("sysconf (_SC_PAGESIZE) failed: %m");
+
+  key_t key = ftok (name, 'G');
+  if (key == -1)
+    FAIL_EXIT1 ("ftok failed: %m");
+
+  shmid = shmget (key, pgsz, IPC_CREAT | IPC_EXCL | SHM_MODE);
+  if (shmid == -1)
+    FAIL_EXIT1 ("shmget failed: %m");
+
+  struct test_shminfo tipcinfo;
+  {
+    uint64_t v = read_proc_file ("/proc/sys/kernel/shmmax");
+#if LONG_MAX == INT_MAX
+    /* Kernel explicit clamp the value for shmmax on compat symbol (32-bit
+       binaries running on 64-bit kernels).  */
+    if (v > INT_MAX)
+      v = INT_MAX;
+#endif
+    tipcinfo.shmmax = v;
+  }
+  tipcinfo.shmall = read_proc_file ("/proc/sys/kernel/shmall");
+  tipcinfo.shmmni = read_proc_file ("/proc/sys/kernel/shmmni");
+
+  int shmidx;
+
+  /* Note: SHM_INFO does not return a shminfo, but rather a 'struct shm_info'.
+     It is tricky to verify its values since the syscall returns system wide
+     resources consumed by shared memory.  The shmctl implementation handles
+     SHM_INFO as IPC_INFO, so the IPC_INFO test should validate SHM_INFO as
+     well.  */
+
+  {
+    struct shminfo ipcinfo;
+    shmidx = shmctl (shmid, IPC_INFO, (struct shmid_ds *) &ipcinfo);
+    if (shmidx == -1)
+      FAIL_EXIT1 ("shmctl with IPC_INFO failed: %m");
+
+    TEST_COMPARE (ipcinfo.shmall, tipcinfo.shmall);
+    TEST_COMPARE (ipcinfo.shmmax, tipcinfo.shmmax);
+    TEST_COMPARE (ipcinfo.shmmni, tipcinfo.shmmni);
+  }
+
+  /* We check if the created shared memory shows in the global list.  */
+  bool found = false;
+  for (int i = 0; i <= shmidx; i++)
+    {
+      /* We can't tell apart if SHM_STAT_ANY is not supported (kernel older
+	 than 4.17) or if the index used is invalid.  So it just check if
+	 value returned from a valid call matches the created message
+	 queue.  */
+      check_shminfo (i, key, SHM_STAT_ANY);
+
+      if (check_shminfo (i, key, SHM_STAT))
+	{
+	  found = true;
+	  break;
+	}
+    }
+
+  if (!found)
+    FAIL_EXIT1 ("shmctl with SHM_STAT/SHM_STAT_ANY could not find the "
+		"created shared memory");
+
+  if (shmctl (shmid, IPC_RMID, NULL) == -1)
+    FAIL_EXIT1 ("shmctl failed");
+
+  return 0;
+}
+
+#include <support/test-driver.c>