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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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1
include/l4/api/kip.h
View File

@@ -95,4 +95,5 @@ struct kip {
extern struct kip kip;
#endif /* __KERNEL__ */
#endif /* __KIP_H__ */

4
include/l4/glue/arm/utcb.h
View File

@@ -8,6 +8,10 @@
#define MR_TOTAL 6
#define MR_TAG 0
#define MR_SENDER 1
#define MR_UNUSED_START 2
/* Compact utcb for now! 8-) */
struct utcb {
u32 mr[MR_TOTAL];

15
src/api/ipc.c
View File

@@ -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;

9
src/arch/arm/exception.c
View File

@@ -16,15 +16,6 @@
#include INC_GLUE(utcb.h)
#include INC_SUBARCH(mm.h)
/*
* NOTE: These are defined in libl4 headers for userspace. Syslib uses
* these as conventional mr offsets to store ipc-related data commonly needed
* for all ipc parties.
*/
#define MR_TAG 0
#define MR_SENDER 1
#define MR_UNUSED_START 2
/* Send data fault ipc to the faulty task's pager */
void fault_ipc_to_pager(u32 faulty_pc, u32 fsr, u32 far)
{

8
tasks/libl4/include/l4lib/arch-arm/syslib.h
View File

@@ -37,11 +37,6 @@ static inline l4id_t l4_get_sender(void)
return (l4id_t)read_mr(MR_SENDER);
}
static inline void l4_set_sender(l4id_t id)
{
write_mr(MR_SENDER, (unsigned int)id);
}
static inline unsigned int l4_get_tag(void)
{
return read_mr(MR_TAG);
@@ -63,7 +58,6 @@ static inline l4id_t self_tid(void)
static inline int l4_send(l4id_t to, unsigned int tag)
{
l4_set_tag(tag);
l4_set_sender(self_tid());
return l4_ipc(to, L4_NILTHREAD);
}
@@ -72,7 +66,7 @@ static inline int l4_sendrecv(l4id_t to, l4id_t from, unsigned int tag)
{
BUG_ON(to == L4_NILTHREAD || from == L4_NILTHREAD);
l4_set_tag(tag);
l4_set_sender(self_tid());
return l4_ipc(to, from);
}