linux-kernel - [PATCH] hugetlb: fix NULL pointer dereference in trace_hugetlbfs_alloc

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Message-Id: <20250106033118.4640-1-songmuchun@bytedance.com>
Date: Mon,  6 Jan 2025 11:31:17 +0800
From: Muchun Song <songmuchun@...edance.com>
To: muchun.song@...ux.dev,
	brauner@...nel.org,
	lihongbo22@...wei.com,
	akpm@...ux-foundation.org
Cc: linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Muchun Song <songmuchun@...edance.com>,
	stable@...r.kernel.org,
	Cheung Wall <zzqq0103.hey@...il.com>
Subject: [PATCH] hugetlb: fix NULL pointer dereference in trace_hugetlbfs_alloc_inode

hugetlb_file_setup() will pass a NULL @dir to hugetlbfs_get_inode(), so
we will access a NULL pointer for @dir. Fix it and set __entry->dr to
0 if @dir is NULL. Because ->i_ino cannot be 0 (see get_next_ino()),
there is no confusing if user sees a 0 inode number.

Fixes: 318580ad7f28 ("hugetlbfs: support tracepoint")
Cc: stable@...r.kernel.org
Reported-by: Cheung Wall <zzqq0103.hey@...il.com>
Closes: https://lore.kernel.org/linux-mm/02858D60-43C1-4863-A84F-3C76A8AF1F15@linux.dev/T/#
Signed-off-by: Muchun Song <songmuchun@...edance.com>
---
 include/trace/events/hugetlbfs.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/trace/events/hugetlbfs.h b/include/trace/events/hugetlbfs.h
index 8331c904a9ba8..59605dfaeeb43 100644
--- a/include/trace/events/hugetlbfs.h
+++ b/include/trace/events/hugetlbfs.h
@@ -23,7 +23,7 @@ TRACE_EVENT(hugetlbfs_alloc_inode,
 	TP_fast_assign(
 		__entry->dev		= inode->i_sb->s_dev;
 		__entry->ino		= inode->i_ino;
-		__entry->dir		= dir->i_ino;
+		__entry->dir		= dir ? dir->i_ino : 0;
 		__entry->mode		= mode;
 	),
 
-- 
2.20.1