[Trusty SRU][PATCH] f2fs: sanity check checkpoint segno and blkoff

[Shrirang Bagul]

From: Jin Qian <jinqian at google.com>

Make sure segno and blkoff read from raw image are valid.

Cc: stable at vger.kernel.org
Signed-off-by: Jin Qian <jinqian at google.com>
[Jaegeuk Kim: adjust minor coding style]
Signed-off-by: Jaegeuk Kim <jaegeuk at kernel.org>

Fixes CVE-2017-10663

(backported from commit 15d3042a937c13f5d9244241c7a9c8416ff6e82a)
Signed-off-by: Shrirang Bagul <shrirang.bagul at canonical.com>
---
 fs/f2fs/super.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index bafff72de8e8..7426751570db 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -724,6 +724,8 @@ static int sanity_check_ckpt(struct f2fs_sb_info *sbi)
 	unsigned int total, fsmeta;
 	struct f2fs_super_block *raw_super = F2FS_RAW_SUPER(sbi);
 	struct f2fs_checkpoint *ckpt = F2FS_CKPT(sbi);
+	unsigned int main_segs, blocks_per_seg;
+	int i;
 
 	total = le32_to_cpu(raw_super->segment_count);
 	fsmeta = le32_to_cpu(raw_super->segment_count_ckpt);
@@ -735,6 +737,20 @@ static int sanity_check_ckpt(struct f2fs_sb_info *sbi)
 	if (fsmeta >= total)
 		return 1;
 
+	main_segs = le32_to_cpu(raw_super->segment_count_main);
+	blocks_per_seg = sbi->blocks_per_seg;
+
+	for (i = 0; i < NR_CURSEG_NODE_TYPE; i++) {
+		if (le32_to_cpu(ckpt->cur_node_segno[i]) >= main_segs ||
+			le16_to_cpu(ckpt->cur_node_blkoff[i]) >= blocks_per_seg)
+			return 1;
+	}
+	for (i = 0; i < NR_CURSEG_DATA_TYPE; i++) {
+		if (le32_to_cpu(ckpt->cur_data_segno[i]) >= main_segs ||
+			le16_to_cpu(ckpt->cur_data_blkoff[i]) >= blocks_per_seg)
+			return 1;
+	}
+
 	if (is_set_ckpt_flags(ckpt, CP_ERROR_FLAG)) {
 		f2fs_msg(sbi->sb, KERN_ERR, "A bug case: need to run fsck");
 		return 1;
-- 
2.11.0