From: Andreas Schwab <schwab@suse•de>
To: Paul Mackerras <paulus@samba•org>
Cc: linuxppc-dev@ozlabs•org, linux-kernel@vger•kernel.org
Subject: Re: [PATCH] Fix msr check in compat_sys_swapcontext
Date: Thu, 06 Nov 2008 11:49:00 +0100 [thread overview]
Message-ID: <jek5bh9lk3.fsf@sykes.suse.de> (raw)
In-Reply-To: <18706.51381.987014.370948@cargo.ozlabs.ibm.com> (Paul Mackerras's message of "Thu, 6 Nov 2008 21:36:37 +1100")
Paul Mackerras <paulus@samba•org> writes:
> Andreas Schwab writes:
>
>> Paul Mackerras <paulus@samba•org> writes:
>>
>> > we need to use get_user, not __get_user, since we haven't done an
>> > access_ok() check on the address.
>>
>> The address is always ok since its a compat pointer, see do_setcontext.
>
> OK, since it's inside a CONFIG_PPC64 block. I'll add a paragraph to
> the patch description pointing that out.
How about this:
diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index a6a4310..b13abf3 100644
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -941,9 +941,21 @@ long sys_swapcontext(struct ucontext __user *old_ctx,
#ifdef CONFIG_PPC64
unsigned long new_msr = 0;
- if (new_ctx &&
- get_user(new_msr, &new_ctx->uc_mcontext.mc_gregs[PT_MSR]))
- return -EFAULT;
+ if (new_ctx) {
+ struct mcontext __user *mcp;
+ u32 cmcp;
+
+ /*
+ * Get pointer to the real mcontext. No need for
+ * access_ok since we are dealing with compat
+ * pointers.
+ */
+ if (__get_user(cmcp, &new_ctx->uc_regs))
+ return -EFAULT;
+ mcp = (struct mcontext __user *)(u64)cmcp;
+ if (__get_user(new_msr, &mcp->mc_gregs[PT_MSR]))
+ return -EFAULT;
+ }
/*
* Check that the context is not smaller than the original
* size (with VMX but without VSX)
Andreas.
--
Andreas Schwab, SuSE Labs, schwab@suse•de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
PGP key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
"And now for something completely different."
prev parent reply other threads:[~2008-11-06 10:49 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-11-05 12:30 [PATCH] Fix msr check in compat_sys_swapcontext Andreas Schwab
2008-11-06 0:52 ` Paul Mackerras
2008-11-06 9:23 ` Andreas Schwab
2008-11-06 10:36 ` Paul Mackerras
2008-11-06 10:49 ` Andreas Schwab [this message]
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