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Kernel inspects and sets sender id instead of userspace.

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Modified ipc handling so that from now on the kernel inspects and sets
the sender id if the receiver is receiving from L4_ANYTHREAD. This posed
a security problem since the receiver could not trust the sender for
sender information.
This commit is contained in:
Bahadir Balban
2008-02-11 11:11:17 +00:00
parent 0c7d2bbfd1
commit e0492d672f
5 changed files with 19 additions and 18 deletions
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15
src/api/ipc.c
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@@ -12,6 +12,7 @@
#include <l4/lib/bit.h>
#include <l4/generic/kmalloc.h>
#include INC_API(syscall.h)
#include INC_GLUE(utcb.h)
enum IPC_TYPE {
IPC_INVALID = 0,
@@ -22,8 +23,12 @@ enum IPC_TYPE {
/*
* Copies message registers from one ktcb stack to another. During the return
* from system call, the registers are popped from the stack. On fast ipc path
* they shouldn't even be pushed to the stack to avoid extra copying.
* from system call, the registers are popped from the stack. In the future
* this should be optimised so that they shouldn't even be pushed to the stack
*
* This also copies the sender into MR0 in case the receiver receives from
* L4_ANYTHREAD. This is done for security since the receiver cannot trust
* the sender info provided by the sender task.
*/
int ipc_msg_copy(struct ktcb *to, struct ktcb *from)
{
@@ -35,6 +40,10 @@ int ipc_msg_copy(struct ktcb *to, struct ktcb *from)
*/
memcpy(mr0_dst, mr0_src, MR_TOTAL * sizeof(unsigned int));
/* Save the sender id in case of ANYTHREAD receiver */
if (to->senderid == L4_ANYTHREAD)
mr0_dst[MR_SENDER] = from->tid;
return 0;
}
@@ -241,6 +250,8 @@ int sys_ipc(struct syscall_args *regs)
ret = -EINVAL;
goto error;
}
/* Cannot send to self, or receive from self */
if (from == current->tid || to == current->tid) {
ret = -EINVAL;
goto error;