Hi kernel hackers,
While looking into msg.c, I noticed that in
sys_msgsnd, there is the test :
if(msgsz + msq->q_cbytes > msq->q_qbytes ||
1 + msq->q_qnum > msq->q_qbytes) {
so that you can send a message only if ressources won't
be exhausted.
The second case means I can send at most MSGMNB messages
to a queue, which is by default 16384.
Now suppose we send messages of length 0 (only type is used).
Knowing that load_msg calls :
msg = (struct msg_msg *) kmalloc (sizeof(*msg) + alen, GFP_KERNEL);
it will result in allocating 36 bytes of memory (suppose we
are on a ia32) per message.
We have 16 queues by default, so if we use the 16 queues this way,
we have :
16 * 36 * 16384 = 9437184, more than 9 MB used.
I hope I am right :-)
Don't you think it is far beyond the 256 KB someone is
expected to be used at maximum for the msg stuff ?
If it is seen as a problem, a solution might be to add
the memory overhead usage into the queue size, or add a
variable that counts the real memory used, and limits it
to a reasonable amount.
C?dric.
PS: I am not on the kernel mailing list, so CC is welcome. (I know it is
bad practice.)
--
main(){int i,j;{printf("\n Who did you say ? Sierpinski ? \n");}
for(i=0;i<80;i++){for(j=0;j<80;j++)printf("%c",i&j?'.':' ');printf("\n");}
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