linux-kernel - [PATCH] f2fs: fix to do sanity check on block address in f2fs_do_zero

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Message-Id: <20220427095140.227316-1-chao@kernel.org>
Date:   Wed, 27 Apr 2022 17:51:40 +0800
From:   Chao Yu <chao@...nel.org>
To:     jaegeuk@...nel.org
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, Chao Yu <chao@...nel.org>,
        stable@...r.kernel.org, Ming Yan <yanming@....edu.cn>,
        Chao Yu <chao.yu@...o.com>
Subject: [PATCH] f2fs: fix to do sanity check on block address in f2fs_do_zero_range()

As Yanming reported in bugzilla:

https://bugzilla.kernel.org/show_bug.cgi?id=215894

I have encountered a bug in F2FS file system in kernel v5.17.

I have uploaded the system call sequence as case.c, and a fuzzed image can
be found in google net disk

The kernel should enable CONFIG_KASAN=y and CONFIG_KASAN_INLINE=y. You can
reproduce the bug by running the following commands:

kernel BUG at fs/f2fs/segment.c:2291!
Call Trace:
 f2fs_invalidate_blocks+0x193/0x2d0
 f2fs_fallocate+0x2593/0x4a70
 vfs_fallocate+0x2a5/0xac0
 ksys_fallocate+0x35/0x70
 __x64_sys_fallocate+0x8e/0xf0
 do_syscall_64+0x3b/0x90
 entry_SYSCALL_64_after_hwframe+0x44/0xae

The root cause is, after image was fuzzed, block mapping info in inode
will be inconsistent with SIT table, so in f2fs_fallocate(), it will cause
panic when updating SIT with invalid blkaddr.

Let's fix the issue by adding sanity check on block address before updating
SIT table with it.

Cc: stable@...r.kernel.org
Reported-by: Ming Yan <yanming@....edu.cn>
Signed-off-by: Chao Yu <chao.yu@...o.com>
---
 fs/f2fs/file.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index f08e6208e183..342b1f17a033 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1437,11 +1437,19 @@ static int f2fs_do_zero_range(struct dnode_of_data *dn, pgoff_t start,
 			ret = -ENOSPC;
 			break;
 		}
-		if (dn->data_blkaddr != NEW_ADDR) {
-			f2fs_invalidate_blocks(sbi, dn->data_blkaddr);
-			dn->data_blkaddr = NEW_ADDR;
-			f2fs_set_data_blkaddr(dn);
+
+		if (dn->data_blkaddr == NEW_ADDR)
+			continue;
+
+		if (!f2fs_is_valid_blkaddr(sbi, dn->data_blkaddr,
+					DATA_GENERIC_ENHANCE)) {
+			ret = -EFSCORRUPTED;
+			break;
 		}
+
+		f2fs_invalidate_blocks(sbi, dn->data_blkaddr);
+		dn->data_blkaddr = NEW_ADDR;
+		f2fs_set_data_blkaddr(dn);
 	}

 	f2fs_update_extent_cache_range(dn, start, 0, index - start);
-- 
2.25.1