From 06b7bcd8cbd7eb1af331e437ec3d8f5182ae1b7e Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <oleg@redhat.com>
Date: Sun, 25 Nov 2012 22:01:42 +0100
Subject: uprobes: Introduce uprobe_is_active()
The lifetime of uprobe->rb_node and uprobe->inode is not refcounted,
delete_uprobe() is called when we detect that uprobe has no consumers,
and it would be deadly wrong to do this twice.
Change delete_uprobe() to WARN() if it was already called. We use
RB_CLEAR_NODE() to mark uprobe "inactive", then RB_EMPTY_NODE() can
be used to detect this case.
RB_EMPTY_NODE() is not used directly, we add the trivial helper for
the next change.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Anton Arapov <anton@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
---
kernel/events/uprobes.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 5d38b40644b8..358baddc8ac2 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -669,6 +669,10 @@ remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, unsigned long vad
return set_orig_insn(&uprobe->arch, mm, vaddr);
}
+static inline bool uprobe_is_active(struct uprobe *uprobe)
+{
+ return !RB_EMPTY_NODE(&uprobe->rb_node);
+}
/*
* There could be threads that have already hit the breakpoint. They
* will recheck the current insn and restart if find_uprobe() fails.
@@ -676,9 +680,13 @@ remove_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, unsigned long vad
*/
static void delete_uprobe(struct uprobe *uprobe)
{
+ if (WARN_ON(!uprobe_is_active(uprobe)))
+ return;
+
spin_lock(&uprobes_treelock);
rb_erase(&uprobe->rb_node, &uprobes_tree);
spin_unlock(&uprobes_treelock);
+ RB_CLEAR_NODE(&uprobe->rb_node); /* for uprobe_is_active() */
iput(uprobe->inode);
put_uprobe(uprobe);
}
--
cgit