[PATCH v9 2/4] Uprobes/sdt: Prevent multiple reference counter for same uprobe

From: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
To: srikar@linux.vnet.ibm.com, oleg@redhat.com, rostedt@goodmis.org,
	mhiramat@kernel.org, liu.song.a23@gmail.com
Cc: peterz@infradead.org, mingo@redhat.com, acme@kernel.org,
	alexander.shishkin@linux.intel.com, jolsa@redhat.com,
	namhyung@kernel.org, linux-kernel@vger.kernel.org,
	ananth@linux.vnet.ibm.com, alexis.berlemont@gmail.com,
	naveen.n.rao@linux.vnet.ibm.com,
	linux-arm-kernel@lists.infradead.org, linux-mips@linux-mips.org,
	linux@armlinux.org.uk, ralf@linux-mips.org, paul.burton@mips.com,
	Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Subject: [PATCH v9 2/4] Uprobes/sdt: Prevent multiple reference counter for same uprobe
Date: Mon, 20 Aug 2018 10:12:48 +0530	[thread overview]
Message-ID: <20180820044250.11659-3-ravi.bangoria@linux.ibm.com> (raw)
In-Reply-To: <20180820044250.11659-1-ravi.bangoria@linux.ibm.com>

We assume to have only one reference counter for one uprobe.
Don't allow user to register multiple uprobes having same
inode+offset but different reference counter.

Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
---
 kernel/events/uprobes.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 35065febcb6c..ecee371a59c7 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -679,6 +679,16 @@ static struct uprobe *insert_uprobe(struct uprobe *uprobe)
 	return u;
 }
 
+static void
+ref_ctr_mismatch_warn(struct uprobe *cur_uprobe, struct uprobe *uprobe)
+{
+	pr_warn("ref_ctr_offset mismatch. inode: 0x%lx offset: 0x%llx "
+		"ref_ctr_offset(old): 0x%llx ref_ctr_offset(new): 0x%llx\n",
+		uprobe->inode->i_ino, (unsigned long long) uprobe->offset,
+		(unsigned long long) cur_uprobe->ref_ctr_offset,
+		(unsigned long long) uprobe->ref_ctr_offset);
+}
+
 static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset,
 				   loff_t ref_ctr_offset)
 {
@@ -698,6 +708,12 @@ static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset,
 	cur_uprobe = insert_uprobe(uprobe);
 	/* a uprobe exists for this inode:offset combination */
 	if (cur_uprobe) {
+		if (cur_uprobe->ref_ctr_offset != uprobe->ref_ctr_offset) {
+			ref_ctr_mismatch_warn(cur_uprobe, uprobe);
+			put_uprobe(cur_uprobe);
+			kfree(uprobe);
+			return ERR_PTR(-EINVAL);
+		}
 		kfree(uprobe);
 		uprobe = cur_uprobe;
 	}
@@ -1112,6 +1128,9 @@ static int __uprobe_register(struct inode *inode, loff_t offset,
 	uprobe = alloc_uprobe(inode, offset, ref_ctr_offset);
 	if (!uprobe)
 		return -ENOMEM;
+	if (IS_ERR(uprobe))
+		return PTR_ERR(uprobe);
+
 	/*
 	 * We can race with uprobe_unregister()->delete_uprobe().
 	 * Check uprobe_is_active() and retry if it is false.
-- 
2.14.4

