Changes from v1: - We should put the modifies of the kprobe after the re-reg check. - And then the address_safe check. - When check_kprobe_address_safe() return fail, the *probed_mod should be set to NULL, and no module refcount held.
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 <[email protected]> --- kernel/kprobes.c | 28 +++++++++------------------- 1 file changed, 9 insertions(+), 19 deletions(-) diff --git a/kernel/kprobes.c b/kernel/kprobes.c index a1606a4..f622639 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; @@ -1501,6 +1488,7 @@ static int check_kprobe_address_safe(struct kprobe *p, * its code to prohibit unexpected unloading. */ if (unlikely(!try_module_get(*probed_mod))) { + *probed_mod = NULL; ret = -ENOENT; goto out; } @@ -1536,9 +1524,13 @@ int register_kprobe(struct kprobe *p) return PTR_ERR(addr); p->addr = addr; - ret = check_kprobe_rereg(p); - if (ret) - return ret; + mutex_lock(&kprobe_mutex); + + /* Return error if the kprobe is being re-registered */ + if (__get_valid_kprobe(p)) { + ret = -EINVAL; + goto out; + } /* User can pass only KPROBE_FLAG_DISABLED to register_kprobe */ p->flags &= KPROBE_FLAG_DISABLED; @@ -1547,9 +1539,7 @@ int register_kprobe(struct kprobe *p) ret = check_kprobe_address_safe(p, &probed_mod); if (ret) - return ret; - - mutex_lock(&kprobe_mutex); + goto out; old_p = get_kprobe(p->addr); if (old_p) { -- 1.8.3.1
