linux-kernel - [PATCH AUTOSEL 4.9 04/30] f2fs: fix to check segment boundary during SIT page readahead

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Message-Id: <20201027001044.1027349-4-sashal@kernel.org>
Date:   Mon, 26 Oct 2020 20:10:18 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Chao Yu <yuchao0@...wei.com>,
        syzbot+3698081bcf0bb2d12174@...kaller.appspotmail.com,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        Sasha Levin <sashal@...nel.org>,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: [PATCH AUTOSEL 4.9 04/30] f2fs: fix to check segment boundary during SIT page readahead

From: Chao Yu <yuchao0@...wei.com>

[ Upstream commit 6a257471fa42c8c9c04a875cd3a2a22db148e0f0 ]

As syzbot reported:

kernel BUG at fs/f2fs/segment.h:657!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 16220 Comm: syz-executor.0 Not tainted 5.9.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:f2fs_ra_meta_pages+0xa51/0xdc0 fs/f2fs/segment.h:657
Call Trace:
 build_sit_entries fs/f2fs/segment.c:4195 [inline]
 f2fs_build_segment_manager+0x4b8a/0xa3c0 fs/f2fs/segment.c:4779
 f2fs_fill_super+0x377d/0x6b80 fs/f2fs/super.c:3633
 mount_bdev+0x32e/0x3f0 fs/super.c:1417
 legacy_get_tree+0x105/0x220 fs/fs_context.c:592
 vfs_get_tree+0x89/0x2f0 fs/super.c:1547
 do_new_mount fs/namespace.c:2875 [inline]
 path_mount+0x1387/0x2070 fs/namespace.c:3192
 do_mount fs/namespace.c:3205 [inline]
 __do_sys_mount fs/namespace.c:3413 [inline]
 __se_sys_mount fs/namespace.c:3390 [inline]
 __x64_sys_mount+0x27f/0x300 fs/namespace.c:3390
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

@blkno in f2fs_ra_meta_pages could exceed max segment count, causing panic
in following sanity check in current_sit_addr(), add check condition to
avoid this issue.

Reported-by: syzbot+3698081bcf0bb2d12174@...kaller.appspotmail.com
Signed-off-by: Chao Yu <yuchao0@...wei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/f2fs/checkpoint.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index c1b24d7aa6ef1..5e9f8ec8251d3 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -201,6 +201,8 @@ int ra_meta_pages(struct f2fs_sb_info *sbi, block_t start, int nrpages,
 					blkno * NAT_ENTRY_PER_BLOCK);
 			break;
 		case META_SIT:
+			if (unlikely(blkno >= TOTAL_SEGS(sbi)))
+				goto out;
 			/* get sit block addr */
 			fio.new_blkaddr = current_sit_addr(sbi,
 					blkno * SIT_ENTRY_PER_BLOCK);
-- 
2.25.1