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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>
This commit is contained in:
Vasilis Liaskovitis 2021-01-15 15:00:11 +01:00 committed by Karel Zak
parent ff21f476f8
commit 7a08784ab0
1 changed files with 12 additions and 6 deletions
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18
sys-utils/ipcs.c
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@ -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;