Bad code path in DoSyscall
mporter at kernel.crashing.org
Tue Nov 11 03:46:24 EST 2003
On Mon, Nov 10, 2003 at 10:56:08AM -0500, John Whitney wrote:
> There seems to be a bad code path in the assembly routine DoSyscall()
> (arch/ppc/kernel/entry.S). In the case of an invalid syscall being made (in
> my case, from user space), DoSyscall is called and eventually branches to
> label 66. Note that before the branch, r12 is set to zero.
> /* disable interrupts so current_thread_info()->flags can't change */
> 30: LOAD_MSR_KERNEL(r10,MSR_KERNEL) /* doesn't include MSR_EE */
> lwz r9,TI_FLAGS(r12)
> Which immediately causes a bad page fault kernel oops. I haven't come up
> with a patch yet, but will try to when I get the time unless someone with
> more knowledge in this area wants to do it. Just wanted to let the list
> know about the problem.
Thanks, here's a patch to grab the thread info when you go down the
no syscall path. This should cure the problem.
It's against linuxppc-2.5. I think that's what you meant since this
bug isn't in 2.4.
===== arch/ppc/kernel/entry.S 1.40 vs edited =====
--- 1.40/arch/ppc/kernel/entry.S Sat Sep 27 03:58:48 2003
+++ edited/arch/ppc/kernel/entry.S Mon Nov 10 09:36:55 2003
@@ -234,6 +234,7 @@
66: li r3,ENOSYS
+ rlwinm r12,r1,0,0,18 /* current_thread_info() */
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