ipcs: Avoid shmall overflows

Avoid computing the number of bytes in shmall, by only
computing and printing the number of Kbytes. This avoids
some overflows, e.g.

$ echo "4503599627370496" > /proc/sys/kernel/shmall
$ ipcs -l | grep 'max total shared memory'
Before:
max total shared memory (kbytes) = 18014398509481980
After:
max total shared memory (kbytes) = 18014398509481984

$ echo "99993599627370500" > /proc/sys/kernel/shmall
99993599627370500
$ ipcs -l | grep 'max total shared memory'
Before:
max total shared memory (kbytes) = 18014398509481980
After:
max total shared memory (kbytes) = 399974398509482000

v1->v2:
  Print the non-overflow KB value only for IPC_UNIT_KB and
IPC_UNIT_DEFAULT.
  This way --bytes and --human options will still get an expected
output
  (but not avoiding the overflow).

Signed-off-by: Vasilis Liaskovitis <vliaskovitis@suse.com>
Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/sys-utils/ipcs.c b/sys-utils/ipcs.c
index fc6fba4a61de19e37cdb6b34b4c71ecc7da951a6..79a6516e6872a4821b7d7ee4fa4c407f1edebe2b 100644 (file)
--- a/sys-utils/ipcs.c
+++ b/sys-utils/ipcs.c
@@ -216,13 +216,19 @@ static void do_shm (char format, int unit)
                ipc_print_size(unit == IPC_UNIT_DEFAULT ? IPC_UNIT_KB : unit,
                               _("max seg size"), lim.shmmax, "\n", 0);
 
-               tmp = (uint64_t) lim.shmall * pgsz;
-               /* overflow handling, at least we don't print ridiculous small values */
-               if (lim.shmall != 0 && tmp / lim.shmall != pgsz) {
-                       tmp = UINT64_MAX - (UINT64_MAX % pgsz);
+               if (unit == IPC_UNIT_KB || unit == IPC_UNIT_DEFAULT) {
+                       ipc_print_size(IPC_UNIT_DEFAULT,
+                              _("max total shared memory (kbytes)"), (pgsz / 1024) *
+                              (uint64_t) lim.shmall, "\n", 0);
+               }
+               else {
+                       tmp = (uint64_t) lim.shmall * pgsz;
+                       /* overflow handling, at least we don't print ridiculous small values */
+                       if (lim.shmall != 0 && tmp / lim.shmall != pgsz)
+                               tmp = UINT64_MAX - (UINT64_MAX % pgsz);
+
+                       ipc_print_size(unit, _("max total shared memory"), tmp, "\n", 0);
                }
-               ipc_print_size(unit == IPC_UNIT_DEFAULT ? IPC_UNIT_KB : unit,
-                              _("max total shared memory"), tmp, "\n", 0);
                ipc_print_size(unit == IPC_UNIT_DEFAULT ? IPC_UNIT_BYTES : unit,
                               _("min seg size"), lim.shmmin, "\n", 0);
                return;