linux-kernel - Re: [syzbot] [ext4?] KASAN: use-after-free Read in ext4_search

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Message-ID: <ZsSh4NUWT7MlvlSL@quatroqueijos.cascardo.eti.br>
Date: Tue, 20 Aug 2024 11:02:08 -0300
From: Thadeu Lima de Souza Cascardo <cascardo@...lia.com>
To: syzbot <syzbot+0c2508114d912a54ee79@...kaller.appspotmail.com>
Cc: linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [ext4?] KASAN: use-after-free Read in ext4_search_dir
 (2)

#syz test: upstream 47ac09b91befbb6a235ab620c32af719f8208399


diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c
index e7a09a99837b..44a5f6df59ec 100644
--- a/fs/ext4/inline.c
+++ b/fs/ext4/inline.c
@@ -1664,24 +1664,36 @@ struct buffer_head *ext4_find_inline_entry(struct inode *dir,
 					struct ext4_dir_entry_2 **res_dir,
 					int *has_inline_data)
 {
+	struct ext4_xattr_ibody_find is = {
+		.s = { .not_found = -ENODATA, },
+	};
+	struct ext4_xattr_info i = {
+		.name_index = EXT4_XATTR_INDEX_SYSTEM,
+		.name = EXT4_XATTR_SYSTEM_DATA,
+	};
 	int ret;
-	struct ext4_iloc iloc;
 	void *inline_start;
 	int inline_size;
 
-	if (ext4_get_inode_loc(dir, &iloc))
-		return NULL;
+	ret = ext4_get_inode_loc(dir, &is.iloc);
+	if (ret)
+		return ERR_PTR(ret);
 
 	down_read(&EXT4_I(dir)->xattr_sem);
+
+	ret = ext4_xattr_ibody_find(dir, &i, &is);
+	if (ret)
+		goto out;
+
 	if (!ext4_has_inline_data(dir)) {
 		*has_inline_data = 0;
 		goto out;
 	}
 
-	inline_start = (void *)ext4_raw_inode(&iloc)->i_block +
+	inline_start = (void *)ext4_raw_inode(&is.iloc)->i_block +
 						EXT4_INLINE_DOTDOT_SIZE;
 	inline_size = EXT4_MIN_INLINE_DATA_SIZE - EXT4_INLINE_DOTDOT_SIZE;
-	ret = ext4_search_dir(iloc.bh, inline_start, inline_size,
+	ret = ext4_search_dir(is.iloc.bh, inline_start, inline_size,
 			      dir, fname, 0, res_dir);
 	if (ret == 1)
 		goto out_find;
@@ -1691,20 +1703,23 @@ struct buffer_head *ext4_find_inline_entry(struct inode *dir,
 	if (ext4_get_inline_size(dir) == EXT4_MIN_INLINE_DATA_SIZE)
 		goto out;
 
-	inline_start = ext4_get_inline_xattr_pos(dir, &iloc);
+	inline_start = ext4_get_inline_xattr_pos(dir, &is.iloc);
 	inline_size = ext4_get_inline_size(dir) - EXT4_MIN_INLINE_DATA_SIZE;
 
-	ret = ext4_search_dir(iloc.bh, inline_start, inline_size,
+	ret = ext4_search_dir(is.iloc.bh, inline_start, inline_size,
 			      dir, fname, 0, res_dir);
 	if (ret == 1)
 		goto out_find;
 
 out:
-	brelse(iloc.bh);
-	iloc.bh = NULL;
+	brelse(is.iloc.bh);
+	if (ret < 0)
+		is.iloc.bh = ERR_PTR(ret);
+	else
+		is.iloc.bh = NULL;
 out_find:
 	up_read(&EXT4_I(dir)->xattr_sem);
-	return iloc.bh;
+	return is.iloc.bh;
 }
 
 int ext4_delete_inline_entry(handle_t *handle,
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 6a95713f9193..14163b32eddb 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -1482,7 +1482,7 @@ static bool ext4_match(struct inode *parent,
 }
 
 /*
- * Returns 0 if not found, -1 on failure, and 1 on success
+ * Returns 0 if not found, -EFSCORRUPTED on failure, and 1 on success
  */
 int ext4_search_dir(struct buffer_head *bh, char *search_buf, int buf_size,
 		    struct inode *dir, struct ext4_filename *fname,
@@ -1503,7 +1503,7 @@ int ext4_search_dir(struct buffer_head *bh, char *search_buf, int buf_size,
 			 * a full check */
 			if (ext4_check_dir_entry(dir, NULL, de, bh, search_buf,
 						 buf_size, offset))
-				return -1;
+				return -EFSCORRUPTED;
 			*res_dir = de;
 			return 1;
 		}
@@ -1511,7 +1511,7 @@ int ext4_search_dir(struct buffer_head *bh, char *search_buf, int buf_size,
 		de_len = ext4_rec_len_from_disk(de->rec_len,
 						dir->i_sb->s_blocksize);
 		if (de_len <= 0)
-			return -1;
+			return -EFSCORRUPTED;
 		offset += de_len;
 		de = (struct ext4_dir_entry_2 *) ((char *) de + de_len);
 	}
@@ -1574,7 +1574,7 @@ static struct buffer_head *__ext4_find_entry(struct inode *dir,
 					     &has_inline_data);
 		if (inlined)
 			*inlined = has_inline_data;
-		if (has_inline_data)
+		if (has_inline_data || IS_ERR(ret))
 			goto cleanup_and_exit;
 	}
 
@@ -1663,8 +1663,10 @@ static struct buffer_head *__ext4_find_entry(struct inode *dir,
 			goto cleanup_and_exit;
 		} else {
 			brelse(bh);
-			if (i < 0)
+			if (i < 0) {
+				ret = ERR_PTR(i);
 				goto cleanup_and_exit;
+			}
 		}
 	next:
 		if (++block >= nblocks)
@@ -1758,7 +1760,7 @@ static struct buffer_head * ext4_dx_find_entry(struct inode *dir,
 		if (retval == 1)
 			goto success;
 		brelse(bh);
-		if (retval == -1) {
+		if (retval < 0) {
 			bh = ERR_PTR(ERR_BAD_DX_DIR);
 			goto errout;
 		}