uprobes: simplify error handling for alloc_uprobe()

Return -ENOMEM instead of NULL, which makes caller's error handling just
a touch simpler.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Reviewed-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20240801132719.GA8788@redhat.com
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 698bb22..e9b092a 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -725,7 +725,7 @@ static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset,
 
 	uprobe = kzalloc(sizeof(struct uprobe), GFP_KERNEL);
 	if (!uprobe)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	uprobe->inode = inode;
 	uprobe->offset = offset;
@@ -1167,8 +1167,6 @@ static int __uprobe_register(struct inode *inode, loff_t offset,
 
  retry:
 	uprobe = alloc_uprobe(inode, offset, ref_ctr_offset);
-	if (!uprobe)
-		return -ENOMEM;
 	if (IS_ERR(uprobe))
 		return PTR_ERR(uprobe);