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Subject[RFC PATCH v4 2/6] uretprobes/x86: hijack return address
Date

hijack the return address and replace it with a "trampoline"

v2:
- remove ->doomed flag, kill task immediately

Signed-off-by: Anton Arapov <anton@redhat.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..c353555 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 rp_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..85e2153 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;
}
+
+extern unsigned long arch_uretprobe_hijack_return_addr(unsigned long
+ rp_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 0;
+
+ /* check whether address has been already hijacked */
+ if (orig_ret_vaddr == rp_trampoline_vaddr)
+ return orig_ret_vaddr;
+
+ ncopied = copy_to_user((void __user *)regs->sp, &rp_trampoline_vaddr, rasize);
+ if (unlikely(ncopied)) {
+ if (ncopied != rasize) {
+ printk(KERN_ERR "uretprobe: 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;
+}
--
1.8.1.2


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