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Subject[RFC PATCH 3/6] 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.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
arch/x86/kernel/uprobes.c | 37 +++++++++++++++----------------------
1 files changed, 15 insertions(+), 22 deletions(-)

diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index dd5f51a..3bcc121 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -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;
-
- if (is_ia32_task())
- rasize = 4;
- else
- rasize = 8;
+ int rasize = sizeof_long();
+ long ra;

- 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;
}
}
@@ -738,23 +733,21 @@ if (ret) pr_crit("EMULATE: %lx -> %lx\n", ip, regs->ip);
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);

--
1.5.5.1


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