[f2fs-dev] [PATCH] f2fs: fix to do sanity check on summary info

[Chao Yu <chao@kernel.org>]

As Wenqing Liu reported in bugzilla:

https://bugzilla.kernel.org/show_bug.cgi?id=216456

BUG: KASAN: use-after-free in recover_data+0x63ae/0x6ae0 [f2fs]
Read of size 4 at addr ffff8881464dcd80 by task mount/1013

CPU: 3 PID: 1013 Comm: mount Tainted: G        W          6.0.0-rc4 #1
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014
Call Trace:
 dump_stack_lvl+0x45/0x5e
 print_report.cold+0xf3/0x68d
 kasan_report+0xa8/0x130
 recover_data+0x63ae/0x6ae0 [f2fs]
 f2fs_recover_fsync_data+0x120d/0x1fc0 [f2fs]
 f2fs_fill_super+0x4665/0x61e0 [f2fs]
 mount_bdev+0x2cf/0x3b0
 legacy_get_tree+0xed/0x1d0
 vfs_get_tree+0x81/0x2b0
 path_mount+0x47e/0x19d0
 do_mount+0xce/0xf0
 __x64_sys_mount+0x12c/0x1a0
 do_syscall_64+0x38/0x90
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

The root cause is: in fuzzed image, SSA table is corrupted: ofs_in_node
is larger than ADDRS_PER_PAGE(), result in out-of-range access on 4k-size
page.

- recover_data
 - do_recover_data
  - check_index_in_prev_nodes
   - f2fs_data_blkaddr

This patch adds sanity check on summary info in recovery and GC flow
in where the flows rely on them.

After patch:
[   29.310883] F2FS-fs (loop0): Inconsistent ofs_in_node:65286 in summary, ino:0, nid:6, max:1018

Cc: <stable@kernel.org>
Reported-by: Wenqing Liu <wenqingliu0120@gmail.com>
Signed-off-by: Chao Yu <chao@kernel.org>
---
 fs/f2fs/gc.c       | 10 +++++++++-
 fs/f2fs/recovery.c | 15 ++++++++++++---
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index fd400d148afb..3a820e5cdaee 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -1078,7 +1078,7 @@ static bool is_alive(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
 {
 	struct page *node_page;
 	nid_t nid;
-	unsigned int ofs_in_node;
+	unsigned int ofs_in_node, max_addrs;
 	block_t source_blkaddr;
 
 	nid = le32_to_cpu(sum->nid);
@@ -1104,6 +1104,14 @@ static bool is_alive(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
 		return false;
 	}
 
+	max_addrs = IS_INODE(node_page) ? DEF_ADDRS_PER_INODE :
+						DEF_ADDRS_PER_BLOCK;
+	if (ofs_in_node >= max_addrs) {
+		f2fs_err(sbi, "Inconsistent ofs_in_node:%u in summary, ino:%u, nid:%u, max:%u",
+			ofs_in_node, dni->ino, dni->nid, max_addrs);
+		return false;
+	}
+
 	*nofs = ofs_of_node(node_page);
 	source_blkaddr = data_blkaddr(NULL, node_page, ofs_in_node);
 	f2fs_put_page(node_page, 1);
diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c
index 8326003e6918..9b361fff30aa 100644
--- a/fs/f2fs/recovery.c
+++ b/fs/f2fs/recovery.c
@@ -474,7 +474,7 @@ static int check_index_in_prev_nodes(struct f2fs_sb_info *sbi,
 	struct dnode_of_data tdn = *dn;
 	nid_t ino, nid;
 	struct inode *inode;
-	unsigned int offset;
+	unsigned int offset, ofs_in_node, max_addrs;
 	block_t bidx;
 	int i;
 
@@ -501,15 +501,24 @@ static int check_index_in_prev_nodes(struct f2fs_sb_info *sbi,
 got_it:
 	/* Use the locked dnode page and inode */
 	nid = le32_to_cpu(sum.nid);
+	ofs_in_node = le16_to_cpu(sum.ofs_in_node);
+
+	max_addrs = ADDRS_PER_PAGE(dn->node_page, dn->inode);
+	if (ofs_in_node >= max_addrs) {
+		f2fs_err(sbi, "Inconsistent ofs_in_node:%u in summary, ino:%u, nid:%u, max:%u",
+			ofs_in_node, ino, nid, max_addrs);
+		return -EFSCORRUPTED;
+	}
+
 	if (dn->inode->i_ino == nid) {
 		tdn.nid = nid;
 		if (!dn->inode_page_locked)
 			lock_page(dn->inode_page);
 		tdn.node_page = dn->inode_page;
-		tdn.ofs_in_node = le16_to_cpu(sum.ofs_in_node);
+		tdn.ofs_in_node = ofs_in_node;
 		goto truncate_out;
 	} else if (dn->nid == nid) {
-		tdn.ofs_in_node = le16_to_cpu(sum.ofs_in_node);
+		tdn.ofs_in_node = ofs_in_node;
 		goto truncate_out;
 	}
 
-- 
2.25.1



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