linux-kernel - [PATCH v3] fs/exfat: resolve memory leak from exfat_create_upcase

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Message-Id: <20240916230506.232137-1-danielyangkang@gmail.com>
Date: Mon, 16 Sep 2024 16:05:06 -0700
From: Daniel Yang <danielyangkang@...il.com>
To: viro@...iv.linux.org.uk,
	Namjae Jeon <linkinjeon@...nel.org>,
	Sungjong Seo <sj1557.seo@...sung.com>,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Daniel Yang <danielyangkang@...il.com>,
	syzbot+e1c69cadec0f1a078e3d@...kaller.appspotmail.com
Subject: [PATCH v3] fs/exfat: resolve memory leak from exfat_create_upcase_table()

    If exfat_load_upcase_table reaches end and returns -EINVAL,
    allocated memory doesn't get freed and while
    exfat_load_default_upcase_table allocates more memory, leading to a    
    memory leak.
    
    Here's link to syzkaller crash report illustrating this issue:
    https://syzkaller.appspot.com/text?tag=CrashReport&x=1406c201980000

Signed-off-by: Daniel Yang <danielyangkang@...il.com>
Reported-by: syzbot+e1c69cadec0f1a078e3d@...kaller.appspotmail.com
---
V2 -> V3: free(NULL) is no-op, removed if() check
V1 -> V2: Moved the mem free to create_upcase_table

 fs/exfat/nls.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/exfat/nls.c b/fs/exfat/nls.c
index afdf13c34..1ac011088 100644
--- a/fs/exfat/nls.c
+++ b/fs/exfat/nls.c
@@ -779,8 +779,11 @@ int exfat_create_upcase_table(struct super_block *sb)
 				le32_to_cpu(ep->dentry.upcase.checksum));
 
 			brelse(bh);
-			if (ret && ret != -EIO)
+			if (ret && ret != -EIO) {
+				/* free memory from exfat_load_upcase_table call */
+				exfat_free_upcase_table(sbi);
 				goto load_default;
+			}
 
 			/* load successfully */
 			return ret;
-- 
2.39.2