[PATCH] kprobes-changed-from-using-spinlock-to-mutex fix

Based on some feedback from Oleg Nesterov, I have made few changes to
previously posted patch.

Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 20 insertions, 19 deletions

diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 331e169e8629..2cd32dd6898b 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -35,7 +35,6 @@
 #include <asm/kdebug.h>
 #include <asm/sstep.h>
 
-static DECLARE_MUTEX(kprobe_mutex);
 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
 
@@ -54,9 +53,7 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
 
         /* insn must be on a special executable page on ppc64 */
         if (!ret) {
-                down(&kprobe_mutex);
                 p->ainsn.insn = get_insn_slot();
-                up(&kprobe_mutex);
                 if (!p->ainsn.insn)
                         ret = -ENOMEM;
         }
diff --git a/arch/x86_64/kernel/kprobes.c b/arch/x86_64/kernel/kprobes.c
index 8b8943bfb89e..128e18190f99 100644
--- a/arch/x86_64/kernel/kprobes.c
+++ b/arch/x86_64/kernel/kprobes.c
@@ -43,7 +43,7 @@
 #include <asm/kdebug.h>
 
 void jprobe_return_end(void);
-void __kprobes arch_copy_kprobe(struct kprobe *p);
+static void __kprobes arch_copy_kprobe(struct kprobe *p);
 
 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
@@ -180,7 +180,7 @@ static inline s32 *is_riprel(u8 *insn)
         return NULL;
 }
 
-void __kprobes arch_copy_kprobe(struct kprobe *p)
+static void __kprobes arch_copy_kprobe(struct kprobe *p)
 {
         s32 *ripdisp;
         memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE);
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index f14ccd35e9b6..f1c0e61a2cb4 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -431,7 +431,7 @@ static int __kprobes register_aggr_kprobe(struct kprobe *old_p,
                 copy_kprobe(old_p, p);
                 ret = add_new_kprobe(old_p, p);
         } else {
-                ap = kcalloc(1, sizeof(struct kprobe), GFP_ATOMIC);
+                ap = kcalloc(1, sizeof(struct kprobe), GFP_KERNEL);
                 if (!ap)
                         return -ENOMEM;
                 add_aggr_kprobe(ap, old_p);
@@ -491,7 +491,8 @@ out:
 void __kprobes unregister_kprobe(struct kprobe *p)
 {
         struct module *mod;
-        struct kprobe *old_p, *cleanup_p;
+        struct kprobe *old_p, *list_p;
+        int cleanup_p;
 
         down(&kprobe_mutex);
         old_p = get_kprobe(p->addr);
@@ -499,22 +500,25 @@ void __kprobes unregister_kprobe(struct kprobe *p)
                 up(&kprobe_mutex);
                 return;
         }
-
-        if ((old_p->pre_handler == aggr_pre_handler) &&
+        if (p != old_p) {
+                list_for_each_entry_rcu(list_p, &old_p->list, list)
+                        if (list_p == p)
+                        /* kprobe p is a valid probe */
+                                goto valid_p;
+                up(&kprobe_mutex);
+                return;
+        }
+valid_p:
+        if ((old_p == p) || ((old_p->pre_handler == aggr_pre_handler) &&
                 (p->list.next == &old_p->list) &&
-                (p->list.prev == &old_p->list)) {
-                /* Only one element in the aggregate list */
+                (p->list.prev == &old_p->list))) {
+                /* Only probe on the hash list */
                 arch_disarm_kprobe(p);
                 hlist_del_rcu(&old_p->hlist);
-                cleanup_p = old_p;
-        } else if (old_p == p) {
-                /* Only one kprobe element in the hash list */
-                arch_disarm_kprobe(p);
-                hlist_del_rcu(&p->hlist);
-                cleanup_p = p;
+                cleanup_p = 1;
         } else {
                 list_del_rcu(&p->list);
-                cleanup_p = NULL;
+                cleanup_p = 0;
         }
 
         up(&kprobe_mutex);
@@ -524,7 +528,7 @@ void __kprobes unregister_kprobe(struct kprobe *p)
                 module_put(mod);
 
         if (cleanup_p) {
-                if (cleanup_p->pre_handler == aggr_pre_handler) {
+                if (p != old_p) {
                         list_del_rcu(&p->list);
                         kfree(old_p);
                 }