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Subject[PATCH] kprobes: avoid the kprobe being re-registered
Date
Old code use check_kprobe_rereg() to check if the kprobe has been
registered already, but check_kprobe_rereg() will release the
kprobe_mutex then, so maybe two paths will pass the check and
register the same kprobe. This patch put the check inside the mutex.

Signed-off-by: Zhou Chengming <zhouchengming1@huawei.com>
---
kernel/kprobes.c | 23 ++++++-----------------
1 file changed, 6 insertions(+), 17 deletions(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index a1606a4..2a4873a 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1443,19 +1443,6 @@ static struct kprobe *__get_valid_kprobe(struct kprobe *p)
return ap;
}

-/* Return error if the kprobe is being re-registered */
-static inline int check_kprobe_rereg(struct kprobe *p)
-{
- int ret = 0;
-
- mutex_lock(&kprobe_mutex);
- if (__get_valid_kprobe(p))
- ret = -EINVAL;
- mutex_unlock(&kprobe_mutex);
-
- return ret;
-}
-
int __weak arch_check_ftrace_location(struct kprobe *p)
{
unsigned long ftrace_addr;
@@ -1536,10 +1523,6 @@ int register_kprobe(struct kprobe *p)
return PTR_ERR(addr);
p->addr = addr;

- ret = check_kprobe_rereg(p);
- if (ret)
- return ret;
-
/* User can pass only KPROBE_FLAG_DISABLED to register_kprobe */
p->flags &= KPROBE_FLAG_DISABLED;
p->nmissed = 0;
@@ -1551,6 +1534,12 @@ int register_kprobe(struct kprobe *p)

mutex_lock(&kprobe_mutex);

+ /* Return error if the kprobe is being re-registered */
+ if (__get_valid_kprobe(p)) {
+ ret = -EINVAL;
+ goto out;
+ }
+
old_p = get_kprobe(p->addr);
if (old_p) {
/* Since this may unoptimize old_p, locking text_mutex. */
--
1.8.3.1
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