linux-kernel - [PATCH] f2fs: add a condition to detect overflow in f2fs_ioc_gc

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Date:   Tue, 17 Sep 2019 10:19:23 +0530
From:   Sahitya Tummala <stummala@...eaurora.org>
To:     Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <yuchao0@...wei.com>,
        linux-f2fs-devel@...ts.sourceforge.net
Cc:     Sahitya Tummala <stummala@...eaurora.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] f2fs: add a condition to detect overflow in f2fs_ioc_gc_range()

end = range.start + range.len;

If the range.start/range.len is a very large value, then end can overflow
in this operation. It results into a crash in get_valid_blocks() when
accessing the invalid range.start segno.

This issue is reported in ioctl fuzz testing.

Signed-off-by: Sahitya Tummala <stummala@...eaurora.org>
---
 fs/f2fs/file.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 5474aaa..c2b4767 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -2123,9 +2123,8 @@ static int f2fs_ioc_gc_range(struct file *filp, unsigned long arg)
 		return -EROFS;
 
 	end = range.start + range.len;
-	if (range.start < MAIN_BLKADDR(sbi) || end >= MAX_BLKADDR(sbi)) {
+	if (end < range.start || range.start < MAIN_BLKADDR(sbi) || end >= MAX_BLKADDR(sbi))
 		return -EINVAL;
-	}
 
 	ret = mnt_want_write_file(filp);
 	if (ret)
-- 
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