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Allow kernel accesses to a small region of the user stack which is used

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by the Linux emulator (and other emulators) for syscall argument
translation. The x86 port currently seems to allow unrestricted kernel
accesses to user memory.

Reviewed by: alc, gallatin
This commit is contained in:
Doug Rabson 1999-12-11 09:58:06 +00:00
parent 273a8aae1c
commit 1c61bdc8eb
1 changed files with 21 additions and 4 deletions
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25
sys/alpha/alpha/trap.c
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@ -39,6 +39,7 @@
#include <sys/signalvar.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/exec.h>
#include <sys/lock.h>
#include <sys/vmmeter.h>
#include <sys/buf.h>
@ -387,11 +388,27 @@ trap(a0, a1, a2, entry, framep)
* 3. pcb_onfault set but kernel space data fault
* The last can occur during an exec() copyin where the
* argument space is lazy-allocated.
*
* For the purposes of the Linux emulator, we allow
* kernel accesses to a small region of the
* user stack which the emulator uses to
* translate syscall arguments.
*/
if (!user && (a0 >= VM_MIN_KERNEL_ADDRESS ||
p == NULL || p->p_addr->u_pcb.pcb_onfault == 0))
map = kernel_map;
else {
if (!user
&& ((a0 >= VM_MIN_KERNEL_ADDRESS)
|| (p == NULL)
|| (p->p_addr->u_pcb.pcb_onfault == 0))) {
if (a0 >= trunc_page(PS_STRINGS
- szsigcode
- SPARE_USRSPACE)
&& a0 < round_page(PS_STRINGS
- szsigcode)) {
vm = p->p_vmspace;
map = &vm->vm_map;
} else {
map = kernel_map;
}
} else {
vm = p->p_vmspace;
map = &vm->vm_map;
}