linux-kernel - [PATCH 3/7] uretprobes/x86: hijack return address

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Message-Id: <1363957745-6657-4-git-send-email-anton@redhat.com>
Date:	Fri, 22 Mar 2013 14:09:00 +0100
From:	Anton Arapov <anton@...hat.com>
To:	Anton Arapov <anton@...hat.com>, Oleg Nesterov <oleg@...hat.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Josh Stone <jistone@...hat.com>,
	Frank Eigler <fche@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	adrian.m.negreanu@...el.com, Torsten.Polle@....de
Subject: [PATCH 3/7] uretprobes/x86: hijack return address

  - Hijack the return address and replace it with a trampoline address.

RFCv5 changes:
  - change the fail return code, because orig_ret_vaddr=0 is possible
  - style fixup
RFCv2 changes:
  - remove ->doomed flag, kill task immediately

Signed-off-by: Anton Arapov <anton@...hat.com>
---
 arch/x86/include/asm/uprobes.h |  1 +
 arch/x86/kernel/uprobes.c      | 29 +++++++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/arch/x86/include/asm/uprobes.h b/arch/x86/include/asm/uprobes.h
index 8ff8be7..6e51979 100644
--- a/arch/x86/include/asm/uprobes.h
+++ b/arch/x86/include/asm/uprobes.h
@@ -55,4 +55,5 @@ extern int  arch_uprobe_post_xol(struct arch_uprobe *aup, struct pt_regs *regs);
 extern bool arch_uprobe_xol_was_trapped(struct task_struct *tsk);
 extern int  arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val, void *data);
 extern void arch_uprobe_abort_xol(struct arch_uprobe *aup, struct pt_regs *regs);
+extern unsigned long arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs *regs);
 #endif	/* _ASM_UPROBES_H */
diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 0ba4cfb..05d357e 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -697,3 +697,32 @@ bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
 		send_sig(SIGTRAP, current, 0);
 	return ret;
 }
+
+unsigned long
+arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs *regs)
+{
+	int rasize, ncopied;
+	unsigned long orig_ret_vaddr = 0; /* clear high bits for 32-bit apps */
+
+	rasize = is_ia32_task() ? 4 : 8;
+	ncopied = copy_from_user(&orig_ret_vaddr, (void __user *)regs->sp, rasize);
+	if (unlikely(ncopied))
+		return -1;
+
+	/* check whether address has been already hijacked */
+	if (orig_ret_vaddr == trampoline_vaddr)
+		return orig_ret_vaddr;
+
+	ncopied = copy_to_user((void __user *)regs->sp, &trampoline_vaddr, rasize);
+	if (unlikely(ncopied)) {
+		if (ncopied != rasize) {
+			printk(KERN_ERR "uprobe: return address clobbered: "
+					"pid=%d, %%sp=%#lx, %%ip=%#lx\n",
+					current->pid, regs->sp, regs->ip);
+			/* kill task immediately */
+			send_sig(SIGSEGV, current, 0);
+		}
+	}
+
+	return orig_ret_vaddr;
+}
-- 
1.8.1.4

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