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Don't allow userland to set hardware watch points on kernel memory at all.

Browse source 
Previously, we tried to allow this only for root.  However, we were calling
suser() on the *target* process rather than the current process.  This
means that if you can ptrace() a process running as root you can set a
hardware watch point in the kernel.  In practice I think you probably have
to be root in order to pass the p_candebug() checks in ptrace() to attach
to a process running as root anyway.  Rather than fix the suser(), I just
axed the entire idea, as I can't think of any good reason _at all_ for
userland to set hardware watch points for KVM.

MFC after:	3 days
Also thinks hardware watch points on KVM from userland are bad:	bde, rwatson
This commit is contained in:
John Baldwin 2006-03-14 16:13:55 +00:00
parent e170bfda56
commit 39092e79ed
3 changed files with 60 additions and 69 deletions
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43
sys/amd64/amd64/machdep.c
View file

@ -1749,8 +1749,7 @@ set_dbregs(struct thread *td, struct dbreg *dbregs)
* could halt the system by setting a breakpoint in the kernel
* (if ddb was enabled). Thus, we need to check to make sure
* that no breakpoints are being enabled for addresses outside
* process's address space, unless, perhaps, we were called by
* uid 0.
* process's address space.
*
* XXX - what about when the watched area of the user's
* address space is written into from within the kernel
@ -1758,27 +1757,25 @@ set_dbregs(struct thread *td, struct dbreg *dbregs)
* from within kernel mode?
*/
if (suser(td) != 0) {
if (dbregs->dr[7] & 0x3) {
/* dr0 is enabled */
if (dbregs->dr[0] >= VM_MAXUSER_ADDRESS)
return (EINVAL);
}
if (dbregs->dr[7] & 0x3<<2) {
/* dr1 is enabled */
if (dbregs->dr[1] >= VM_MAXUSER_ADDRESS)
return (EINVAL);
}
if (dbregs->dr[7] & 0x3<<4) {
/* dr2 is enabled */
if (dbregs->dr[2] >= VM_MAXUSER_ADDRESS)
return (EINVAL);
}
if (dbregs->dr[7] & 0x3<<6) {
/* dr3 is enabled */
if (dbregs->dr[3] >= VM_MAXUSER_ADDRESS)
return (EINVAL);
}
if (dbregs->dr[7] & 0x3) {
/* dr0 is enabled */
if (dbregs->dr[0] >= VM_MAXUSER_ADDRESS)
return (EINVAL);
}
if (dbregs->dr[7] & 0x3<<2) {
/* dr1 is enabled */
if (dbregs->dr[1] >= VM_MAXUSER_ADDRESS)
return (EINVAL);
}
if (dbregs->dr[7] & 0x3<<4) {
/* dr2 is enabled */
if (dbregs->dr[2] >= VM_MAXUSER_ADDRESS)
return (EINVAL);
}
if (dbregs->dr[7] & 0x3<<6) {
/* dr3 is enabled */
if (dbregs->dr[3] >= VM_MAXUSER_ADDRESS)
return (EINVAL);
}
pcb->pcb_dr0 = dbregs->dr[0];

43
sys/i386/i386/machdep.c
View file

@ -2801,8 +2801,7 @@ set_dbregs(struct thread *td, struct dbreg *dbregs)
* could halt the system by setting a breakpoint in the kernel
* (if ddb was enabled). Thus, we need to check to make sure
* that no breakpoints are being enabled for addresses outside
* process's address space, unless, perhaps, we were called by
* uid 0.
* process's address space.
*
* XXX - what about when the watched area of the user's
* address space is written into from within the kernel
@ -2810,30 +2809,28 @@ set_dbregs(struct thread *td, struct dbreg *dbregs)
* from within kernel mode?
*/
if (suser(td) != 0) {
if (dbregs->dr[7] & 0x3) {
/* dr0 is enabled */
if (dbregs->dr[0] >= VM_MAXUSER_ADDRESS)
return (EINVAL);
}
if (dbregs->dr[7] & 0x3) {
/* dr0 is enabled */
if (dbregs->dr[0] >= VM_MAXUSER_ADDRESS)
return (EINVAL);
}
if (dbregs->dr[7] & (0x3<<2)) {
/* dr1 is enabled */
if (dbregs->dr[1] >= VM_MAXUSER_ADDRESS)
return (EINVAL);
}
if (dbregs->dr[7] & (0x3<<2)) {
/* dr1 is enabled */
if (dbregs->dr[1] >= VM_MAXUSER_ADDRESS)
return (EINVAL);
}
if (dbregs->dr[7] & (0x3<<4)) {
/* dr2 is enabled */
if (dbregs->dr[2] >= VM_MAXUSER_ADDRESS)
return (EINVAL);
}
if (dbregs->dr[7] & (0x3<<4)) {
/* dr2 is enabled */
if (dbregs->dr[2] >= VM_MAXUSER_ADDRESS)
return (EINVAL);
}
if (dbregs->dr[7] & (0x3<<6)) {
/* dr3 is enabled */
if (dbregs->dr[3] >= VM_MAXUSER_ADDRESS)
return (EINVAL);
}
if (dbregs->dr[7] & (0x3<<6)) {
/* dr3 is enabled */
if (dbregs->dr[3] >= VM_MAXUSER_ADDRESS)
return (EINVAL);
}
pcb->pcb_dr0 = dbregs->dr[0];

43
sys/pc98/pc98/machdep.c
View file

@ -2632,8 +2632,7 @@ set_dbregs(struct thread *td, struct dbreg *dbregs)
* could halt the system by setting a breakpoint in the kernel
* (if ddb was enabled). Thus, we need to check to make sure
* that no breakpoints are being enabled for addresses outside
* process's address space, unless, perhaps, we were called by
* uid 0.
* process's address space.
*
* XXX - what about when the watched area of the user's
* address space is written into from within the kernel
@ -2641,30 +2640,28 @@ set_dbregs(struct thread *td, struct dbreg *dbregs)
* from within kernel mode?
*/
if (suser(td) != 0) {
if (dbregs->dr[7] & 0x3) {
/* dr0 is enabled */
if (dbregs->dr[0] >= VM_MAXUSER_ADDRESS)
return (EINVAL);
}
if (dbregs->dr[7] & 0x3) {
/* dr0 is enabled */
if (dbregs->dr[0] >= VM_MAXUSER_ADDRESS)
return (EINVAL);
}
if (dbregs->dr[7] & (0x3<<2)) {
/* dr1 is enabled */
if (dbregs->dr[1] >= VM_MAXUSER_ADDRESS)
return (EINVAL);
}
if (dbregs->dr[7] & (0x3<<2)) {
/* dr1 is enabled */
if (dbregs->dr[1] >= VM_MAXUSER_ADDRESS)
return (EINVAL);
}
if (dbregs->dr[7] & (0x3<<4)) {
/* dr2 is enabled */
if (dbregs->dr[2] >= VM_MAXUSER_ADDRESS)
return (EINVAL);
}
if (dbregs->dr[7] & (0x3<<4)) {
/* dr2 is enabled */
if (dbregs->dr[2] >= VM_MAXUSER_ADDRESS)
return (EINVAL);
}
if (dbregs->dr[7] & (0x3<<6)) {
/* dr3 is enabled */
if (dbregs->dr[3] >= VM_MAXUSER_ADDRESS)
return (EINVAL);
}
if (dbregs->dr[7] & (0x3<<6)) {
/* dr3 is enabled */
if (dbregs->dr[3] >= VM_MAXUSER_ADDRESS)
return (EINVAL);
}
pcb->pcb_dr0 = dbregs->dr[0];