Commit 8faaed1b authored by Oleg Nesterov's avatar Oleg Nesterov
Browse files

uprobes/x86: Introduce sizeof_long(), cleanup adjust_ret_addr() and... 


uprobes/x86: Introduce sizeof_long(), cleanup adjust_ret_addr() and arch_uretprobe_hijack_return_addr()

1. Add the trivial sizeof_long() helper and change other callers of
   is_ia32_task() to use it.

   TODO: is_ia32_task() is not what we actually want, TS_COMPAT does
   not necessarily mean 32bit. Fortunately syscall-like insns can't be
   probed so it actually works, but it would be better to rename and
   use is_ia32_frame().

2. As Jim pointed out "ncopied" in arch_uretprobe_hijack_return_addr()
   and adjust_ret_addr() should be named "nleft". And in fact only the
   last copy_to_user() in arch_uretprobe_hijack_return_addr() actually
   needs to inspect the non-zero error code.

TODO: adjust_ret_addr() should die. We can always calculate the value
we need to write into *regs->sp, just UPROBE_FIX_CALL should record
insn->length.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Reviewed-by: default avatarJim Keniston <jkenisto@us.ibm.com>
parent 75f9ef0b

arch/x86/kernel/uprobes.c

+15 −22
Original line number Diff line number Diff line
@@ -408,6 +408,11 @@ struct uprobe_xol_ops { 
	int	(*post_xol)(struct arch_uprobe *, struct pt_regs *);

};



static inline int sizeof_long(void)

{

	return is_ia32_task() ? 4 : 8;

}



static int default_pre_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs)

{

	pre_xol_rip_insn(auprobe, regs, &current->utask->autask);
@@ -419,21 +424,14 @@ static int default_pre_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs) 
 */

static int adjust_ret_addr(unsigned long sp, long correction)

{

	int rasize, ncopied;

	long ra = 0;

	int rasize = sizeof_long();

	long ra;



	if (is_ia32_task())

		rasize = 4;

	else

		rasize = 8;



	ncopied = copy_from_user(&ra, (void __user *)sp, rasize);

	if (unlikely(ncopied))

	if (copy_from_user(&ra, (void __user *)sp, rasize))

		return -EFAULT;



	ra += correction;

	ncopied = copy_to_user((void __user *)sp, &ra, rasize);

	if (unlikely(ncopied))

	if (copy_to_user((void __user *)sp, &ra, rasize))

		return -EFAULT;



	return 0;
@@ -450,10 +448,7 @@ static int default_post_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs 


	if (auprobe->fixups & UPROBE_FIX_CALL) {

		if (adjust_ret_addr(regs->sp, correction)) {

			if (is_ia32_task())

				regs->sp += 4;

			else

				regs->sp += 8;

			regs->sp += sizeof_long();

			return -ERESTART;

		}

	}
@@ -714,23 +709,21 @@ bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs) 
unsigned long

arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs *regs)

{

	int rasize, ncopied;

	int rasize = sizeof_long(), nleft;

	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))

	if (copy_from_user(&orig_ret_vaddr, (void __user *)regs->sp, rasize))

		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 (likely(!ncopied))

	nleft = copy_to_user((void __user *)regs->sp, &trampoline_vaddr, rasize);

	if (likely(!nleft))

		return orig_ret_vaddr;



	if (ncopied != rasize) {

	if (nleft != rasize) {

		pr_err("uprobe: return address clobbered: pid=%d, %%sp=%#lx, "

			"%%ip=%#lx\n", current->pid, regs->sp, regs->ip);

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