uprobes/tracing: Ensure inode != NULL in create_trace_uprobe()

probe_event_enable/disable() check tu->inode != NULL at the start.
This is ugly, if igrab() can fail create_trace_uprobe() should not
succeed and "postpone" the failure.

And S_ISREG(inode->i_mode) check added by d24d7dbf is not safe.

Note: alloc_uprobe() should probably check igrab() != NULL as well.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 15b8eceeddc5e3801543606b7feeea9e866ba8fd..f7838cfd61b9393b7241ff5904f35d9ac217d16e 100644 (file)
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -256,7 +256,7 @@ static int create_trace_uprobe(int argc, char **argv)
        inode = igrab(path.dentry->d_inode);
        path_put(&path);
 
-       if (!S_ISREG(inode->i_mode)) {
+       if (!inode || !S_ISREG(inode->i_mode)) {
                ret = -EINVAL;
                goto fail_address_parse;
        }
@@ -544,7 +544,7 @@ static int probe_event_enable(struct trace_uprobe *tu, int flag)
        struct uprobe_trace_consumer *utc;
        int ret = 0;
 
-       if (!tu->inode || tu->consumer)
+       if (tu->consumer)
                return -EINTR;
 
        utc = kzalloc(sizeof(struct uprobe_trace_consumer), GFP_KERNEL);
@@ -568,7 +568,7 @@ static int probe_event_enable(struct trace_uprobe *tu, int flag)
 
 static void probe_event_disable(struct trace_uprobe *tu, int flag)
 {
-       if (!tu->inode || !tu->consumer)
+       if (!tu->consumer)
                return;
 
        uprobe_unregister(tu->inode, tu->offset, &tu->consumer->cons);