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Message-Id: <20240702132349.2600605-3-libaokun@huaweicloud.com>
Date: Tue, 2 Jul 2024 21:23:49 +0800
From: libaokun@...weicloud.com
To: linux-ext4@...r.kernel.org
Cc: tytso@....edu,
adilger.kernel@...ger.ca,
jack@...e.cz,
ritesh.list@...il.com,
linux-kernel@...r.kernel.org,
yi.zhang@...wei.com,
yangerkun@...wei.com,
libaokun@...weicloud.com,
Baokun Li <libaokun1@...wei.com>,
syzbot+ae688d469e36fb5138d0@...kaller.appspotmail.com,
stable@...nel.org
Subject: [PATCH 2/2] ext4: make sure the first directory block is not a hole
From: Baokun Li <libaokun1@...wei.com>
The syzbot constructs a directory that has no dirblock but is non-inline,
i.e. the first directory block is a hole. And no errors are reported when
creating files in this directory in the following flow.
ext4_mknod
...
ext4_add_entry
// Read block 0
ext4_read_dirblock(dir, block, DIRENT)
bh = ext4_bread(NULL, inode, block, 0)
if (!bh && (type == INDEX || type == DIRENT_HTREE))
// The first directory block is a hole
// But type == DIRENT, so no error is reported.
After that, we get a directory block without '.' and '..' but with a valid
dentry. This may cause some code that relies on dot or dotdot (such as
make_indexed_dir()) to crash.
Therefore when ext4_read_dirblock() finds that the first directory block
is a hole report that the filesystem is corrupted and return an error to
avoid loading corrupted data from disk causing something bad.
Reported-by: syzbot+ae688d469e36fb5138d0@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=ae688d469e36fb5138d0
Fixes: 4e19d6b65fb4 ("ext4: allow directory holes")
Cc: stable@...nel.org
Signed-off-by: Baokun Li <libaokun1@...wei.com>
---
fs/ext4/namei.c | 17 ++++++-----------
1 file changed, 6 insertions(+), 11 deletions(-)
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 35881e3dd880..6a95713f9193 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -151,10 +151,11 @@ static struct buffer_head *__ext4_read_dirblock(struct inode *inode,
return bh;
}
- if (!bh && (type == INDEX || type == DIRENT_HTREE)) {
+ /* The first directory block must not be a hole. */
+ if (!bh && (type == INDEX || type == DIRENT_HTREE || block == 0)) {
ext4_error_inode(inode, func, line, block,
- "Directory hole found for htree %s block",
- (type == INDEX) ? "index" : "leaf");
+ "Directory hole found for htree %s block %u",
+ (type == INDEX) ? "index" : "leaf", block);
return ERR_PTR(-EFSCORRUPTED);
}
if (!bh)
@@ -3084,10 +3085,7 @@ bool ext4_empty_dir(struct inode *inode)
EXT4_ERROR_INODE(inode, "invalid size");
return false;
}
- /* The first directory block must not be a hole,
- * so treat it as DIRENT_HTREE
- */
- bh = ext4_read_dirblock(inode, 0, DIRENT_HTREE);
+ bh = ext4_read_dirblock(inode, 0, EITHER);
if (IS_ERR(bh))
return false;
@@ -3529,10 +3527,7 @@ static struct buffer_head *ext4_get_first_dir_block(handle_t *handle,
struct ext4_dir_entry_2 *de;
unsigned int offset;
- /* The first directory block must not be a hole, so
- * treat it as DIRENT_HTREE
- */
- bh = ext4_read_dirblock(inode, 0, DIRENT_HTREE);
+ bh = ext4_read_dirblock(inode, 0, EITHER);
if (IS_ERR(bh)) {
*retval = PTR_ERR(bh);
return NULL;
--
2.39.2
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